Low Tunnels

by: Dean Gunderson

One of the most adaptable items in the gardens is a good set of wire or pvc hoops to create low tunnels.  Depending on what fabric goes over your low tunnel hoops it can protect crops from early or late frosts, overwinter cold hardy crops, shade crops to keep them cooler in summer and fall, minimize pests, or minimize disease. 

So what is a low tunnel?  Low tunnels, also called quick hoops, are like a small greenhouse that covers a raised bed or rows of in ground plantings that you can’t walk into, unlike a greenhouse or high tunnel.  The structure of the low tunnel that holds the fabric up is usually made of wire or pvc pipes and are bent into an arch shape and just pushed into the ground at the edges of the raised bed or on the edges of the in ground rows of plants.  These hoops hold the fabric material up above the plants so the fabric isn’t just laying on the leaves of the plants.  The fabric it pulled taught and secured to the ground to hold it in place.

How to Build a Low Tunnel

The first step of building a low tunnel is putting the hoops in.  You can use any material that can be made into an arch but the most popular is a heavy wire, which you can bend into a hoop or can be purchased prebent, like these.  Another readily accessible material that can easily be bent into an arch is a thin pvc pipe.  You just push the ends of the hoops into the ground at least 4”-6”.  You should place one hoop on each end of the raised bed or planting row and then another hoop every 3-4’ between those end hoops.  

Wire hoops ready to be covered with low tunnel plastic
Wire hoops ready to be covered with low tunnel plastic

Then cut your cover fabric of choice 4’ longer than the bed or row you are trying to cover and drape it over the hoops (different fabric options and the uses for each type will be discussed later). 

Draping the low tunnel plastic over the wire hoops
Draping the low tunnel plastic over the wire hoops
Low tunnel plastic in place and ready to be secured
The low tunnel plastic is in place and ready to be secured with sod staples or bricks

Then secure the ends of the fabric to the ground.  This can be done in several ways.  The cheapest and simplest is just to put rocks or bricks all along the ends of the fabric to weight it down to the ground.  You can also secure the fabric with sod staples, like these.  Just bundle up the ends of your fabric and push the staple through the bundled edge and all the way down into the soil.  Space these staples every 9”-12” along the sides that don’t need to be opened regularly.  Knowing if it needs to be opened regularly brings us to management considerations.

showing pushing the sod staple through bundled up plastic to secure it
This is how you bundle up the fabric on the end and apply the sod staple
Showing that you want to push the staple all the way into the soil
Make sure you push the staple all the way through the plastic and down into the soil to hold the plastic down tight.

One of the most important things to remember is that you need to access the plants under the low tunnel.  So you can put the sod staples all the way around the low tunnel but it might be easier to do sod staples on both short sides and one long side but use rocks on the other long side so it’s easier to open and close that size so you have easy access to your plants.  Another thing to remember is that if you are covering the plants to protect from frost for season extension in spring and/or fall remember that our weather can swing wildly in St. Louis in those seasons so having the cover on when it’s cold is important but if then there is a day that is a little warmer, even if it’s not hot, but it’s sunny the plants can actually overheat just like a car sitting in the sun.  So especially those times of years you might need to vent your low tunnel.  This would mean opening up an end of the tunnel during the morning and then closing it again in the evening if it will be cold that night.

The Fabric Options

There are several different options of material to cover the low tunnel with and, which material to use depends on what the goals are.  Below are 4 different cover options for a low tunnel.  Each section describes the material, what it can be used for, and how to manage a low tunnel for that use.

  1. Insect Netting: This mesh material is great for covering crops if you are trying to keep pests away from your crops, especially in the summer.  It is airy enough that it doesn’t cast shade and also doesn’t retain heat.  It is also airy enough that rain will go through it so you don’t need to open the low tunnel to vent heat or to water your plants with insect netting.  This can be especially helpful to set up and put over brassica crops to keep out cabbage worms and cabbage loopers and to put over squash to keep out squash vine borers.  It can really be used over any plant to keep out pests and the diseases those pests might be carrying.  The main thing to keep in mind with using insect netting is that a net that keeps out pest insects will also keep out pollinators.  So if you need pollinators in order for your crop to produce, like with squash, you will need to remove the netting once the plant starts flowering or you will need to hand pollinate.  An important note about insect netting is that it is best to cover your plants as soon as you plant them.  If you wait there is the possibility that the insects will already have laid eggs in the soil or on the plant and then if you put the barrier over you are trapping the pest in with your plant.
  2. Low Tunnel Plastic: This plastic is simply sheet plastic that can be put over low tunnel hoops for season extension and/or overwintering.  This type of plastic is perfect for putting on in early spring to warm up the soil faster in order to plant sooner or putting on in late fall to keep the soil warm longer in order to continue harvesting later in the year.  If put up in late fall over cold hardy crops it can help to overwinter those crops so they can be harvested all winter long.  Clear plastic will heat up more than white plastic but both are used.  Plastic is the material that will heat up the most so is the best option if you are tying to overwinter crops.  Since plastic doesn’t allow air flow it will definitely need to be vented on sunny days to prevent overheating especially in the spring and fall if used for season extension.  There are also types of low tunnel plastic that have either slits or holes punched in it to prevent overheating, like this low tunnel plastic.  These types don’t need to be vented manually.  Plastic also doesn’t allow rain to go through it so you will periodically need to open it up to water the plants.
  3. Shade Cloth: This material looks like a loose weave mesh and is usually made of a colored plastic material, oftentimes black.  It is designed to cast shade on the crops underneath it.  Shade is particularly helpful in late spring-early summer when trying to keep your spring crops cool so they are less liable to bolt and will keep producing as it starts getting hot.  It can also be put on in late summer in order to keep your fall crops cool as the seeds germinate and start growing in the hot sun of summer.  As this is just to cast shade it doesn’t need to go all the way to the ground and leaving some gaps at the bottom helps increase airflow.  As it is a loose mesh rain will go through to water the crops.
  4. Row Cover: This is maybe the most adaptable cover for a low tunnel.  It can be used for all 3 of the things the above fabrics can be used for but generally not as good as the fabric that is specially for those 3 things.  It is a spun fabric that looks similar to the type of fabric that dryer sheets are made of.  It traps heat and therefore is often used for season extension.  For protecting from early or late frosts it is generally easier to used than plastic because is less liable to overheat but it is not as good for overwintering because it doesn’t trap as much heat and allows more airflow increasing cold winds.  It is also nicer than plastic in regards to watering because it allows rain to get through which plastic doesn’t.  Row cover also casts shade but only about 15% whereas most shade cloth for vegetables is 30%-40% shade so if doubled or tripled up it could serve as this purpose a little better.  However, as it does trap heat unless you can allow a lot of airflow it can actually be counterproductive if you are casting shade to try and keep things cool.  It is also good as an insect barrier.  In this regard it does just as good of a job as insect netting with all of the same considerations discussed above when it comes to insect netting.  The main problem with using row cover to keep insects out is that as mentioned it also retains heat so can cause overheating when trying to cover squash, brassicas, or any other crop in the middle of summer, when there are so many pests.

Another thing to consider when it comes to selecting and using your low tunnel fabric is that you don’t necessarily have to just do one layer or even just one type of fabric.  As mentioned you could double or triple up row cover to make it cast more shade.  It is also common to do multiple layers of row cover in order to increase how much insulation it provides to protect crops from lower temperatures.  A similar thing can be done with plastic.  Doing two layers of plastic will protect the crops they cover from lower temperatures than a single layer of plastic.  This works because the air between the two layers of plastic acts like an insulation layer.  If you are trying to protect your brassicas from cabbage worms and loopers and also want to cast some shade to help them through the heat of summer you could put on a layer of insect netting and then a layer of shade cloth on top.  

All in all the next time you have an issue in the garden don’t overlook how useful a low tunnel can be and maybe consider using one to increase your yields and lower your work load.

Demonstration Garden Update August 19, 2020

by: Dean Gunderson

This has been an interesting year in the demonstration garden for sure. We miss all the people we usually get to see on Saturdays so wanted to give everyone an update on some successes and failures so far this year. Our biggest challenge was for several months we didn’t have any of our wonderful volunteers to help us and we were struggling.  Thankfully we are now able to have some volunteer help and it has been incredibly beneficial in getting the garden growing beautifully.  Our other challenges are things that I’m sure many of you have been dealing with in your own gardens. The frequent heavy rains have led to a lot of our tomatoes splitting and our brassicas have been inundated by cabbage worms, cabbage loopers, and harlequin beetles. We also have a seemingly endless number of rabbits that have forced us to put fencing up around nearly every bed to prevent them from eating absolutely everything. These issues have forced us to be more vigilant about getting our fencing up, picking off harlequin bugs, cabbage worms, and cabbage loopers, and using DE and BT when necessary to control those pests.

An image of one of a caterpillar eating a collard leaf and the damage they cause.
One of the several types of caterpillars that like to eat brassicas such as collards and cabbage.

Despite these challenges we have been able to grow some really delicious produce that is being donated to a local food pantry in East St. Louis every week. We have also done experiments that have already yielded interesting results and have several more in process that are progressing nicely. 

Cauliflower is a vegetable that is one of the hardest vegetables to grow in St. Louis’ climate for most gardeners we know.  So this spring we did a cauliflower trial in an attempt to find one that would be easy to grow in St. Louis.  We selected varieties that were stated to be heat tolerant and fast maturing.  They were all disappointing……except one. The variety named ‘Minuteman’ produced a small, but decent sized, head of cauliflower. We harvested the heads in late June, at which point they had endured 12 days of 90F degree or higher temperatures and yet the heads were still tender and delicious. So we are doing a larger planting of ‘Minuteman’ this fall to see how well it does as a fall-planted variety here.

A picture of our 'Minuteman' cauliflower head with a hand next to it for scale.  It's about 4-5" in diameter
Our first head of ‘Minuteman’ cauliflower from our trial

In addition to the cauliflower trial, we are also growing several different types of white-fleshed and purple-fleshed sweet potatoes.  We selected varieties that are claimed to mature in a similar number of days to the ever popular orange-fleshed ‘Beauregard’ sweet potato that we have always grown to see how they compare and if they would be good varieties to start growing regularly.  So far they are all growing well so stay tuned for the update this fall when we harvest and do the comparison.

A few years ago we started on the adventure of making a “paddy” and growing flooded rice and it has been very successful (you can read all about it on our blog if you are interested).  So this year we decided to go bigger and try other aquatic edible crops. We are growing water chestnuts in two flooded old plastic kiddie pools.  We are also growing wapato (aka duck potato) in an old tank we used to use to wash lettuce.  Water chestnuts and wapato both create nice crunchy edible tubers. We are also growing 4 different types water lotus. We are growing one tank with the native water lotus and three domesticated varieties of the Asian water lotus. Water lotus create large crunchy tubers similar in flavor and texture to a water chestnut but also create really interesting leaves and gorgeous flowers during the growing season that give way to seed pods with edible seeds.

A pictures showing water lotus, rice, and water chestnuts growing
Water lotus blooming with our rice paddy in the background with rice on the left and water chestnuts on the right.

Gateway Greening’s Growing Gardeners Contest

For the month of July, we want to challenge youth gardeners to engineer an original solution to a problem in the garden. Send in your pictures or videos and a written description and we will choose a winner at the end of the month. The contest is open to students entering grades 2-5 and students entering grades 6-8. Winners will be featured on Gateway Greening’s social media pages and receive a Gateway Greening stuffed gardener bear or a Gateway Greening t-shirt! See below for contest details.

Grades 2-5

July: Engineering in the Garden

Plants need space in order to be happy and healthy, but you do not need a big yard or a garden bed to grow a plant! Many people use small containers to grow vegetables and herbs on their porch or in their windowsill. 

Scientists use the word engineering to describe the process of creating a solution to a problem. For the month of July, we want to see what creative ways you can find to grow plants in a small space. Find a container to repurpose as a planter or build your own! Then fill it with soil and drop a few seeds of your choice in it. Be sure to give it lots of water and sunshine. Send in your pictures or videos of your new planter with a written description of how you created it, and we will choose a winner at the end of the month. 


Who: Open to students entering grades 2-5

What: Engineer a solution to gardening in a small space by creating a planter or repurposing something you already have as a planter. Submit photos or videos of your new planter and a written paragraph explaining how you created it. Include your full name, contact information, school, and the grade you will be entering in fall 2020 in your email. 

When: Entries must be submitted via email by July 31st. The winner will be contacted by August 7th. 

Where: Submit entries to [email protected] with the subject line “July Youth Contest 2-5”

Winner will be determined based on creativity and resourcefulness. Upon receiving permission from your guardian to share your name and photos, winners will be featured on Gateway Greening’s social media account and receive their choice of either a Gateway Greening stuffed gardener bear or a Gateway Greening t-shirt.

Happy engineering!

For inspiration, see some of the containers Gateway Greening has turned into planters at our Demonstration Garden! 

Grades 6-8

July: Engineering in the Garden

Watching the plants in your garden grow from tiny sprouts to towering fruit-bearing plants sure is fun! But even the strongest plants have competition from predators. Pests like beetles and caterpillars love to munch the leaves of plants, while birds, rabbits, and squirrels will sometimes eat the seeds, fruits, or other parts of the plant. This pesky problem leaves gardeners in need of solutions. 

Scientists use the word engineering to describe the process of creating a solution to a problem.  For the month of July, we want to challenge youth gardeners to engineer an original solution to a pest problem in the garden. Send in your pictures or videos and a written description and we will choose a winner at the end of the month. 


Who: Open to students entering grades 6-8

What: Engineer a solution to a pest problem in the garden. Submit photos or videos of your solution and a written paragraph explaining your solution. Include your full name, contact information, school, and the grade you will be entering in fall 2020 in your email. 

When: Entries must be submitted via email by July 31st. The winner will be contacted by August 7th. 

Where: Submit entries to [email protected] with the subject line “July Youth Contest 6-8”

Winner will be determined based on creativity and resourcefulness. Upon receiving permission from your guardian to share your name and photos, winners will be featured on Gateway Greening’s social media account and receive a Gateway Greening stuffed gardener bear or a Gateway Greening t-shirt.

Happy engineering!

For inspiration, see some of the ways Gateway Greening keeps pests out of garden beds using fencing and onions along the perimeter of the beds.

The Ever Controversial Japanese Beetle Trap

by: Dean Gunderson

To trap or not to trap, that is the ever present question when it comes to Japanese beetles. The shiny green Japanese beetle was introduced to the northeastern United States from East Asia in the early 1900’s and has made its slow march south and west ever since. It has been in the St. Louis region for quite some time now and most gardeners have had at least one run in with this pernicious pest. Although it doesn’t feed on many vegetable crops it likes quite a few fruit trees and shrubs. These voracious eaters can defoliate whole plants if allowed. The way they eat leaves is pretty characteristic as when they feed on leaves they will eat everything except the veins of the leaves leaving a skeletonized leaf behind.  

characteristic Japanese beetle leaf damage
Characteristic Japanese beetle leaf damage on a hazelnut bush

The hardest thing about Japanese beetles isn’t identifying them or figuring out what damage they do, it’s how to get rid of them! Since they are an invasive species they have very few predators so their populations can get quite large and controlling them is left to the gardener or orchardist.  

But what is the best way to control the population? You could, of course, use synthetic insecticides or organic broad spectrum insecticides such as spinosad or pyrethum. However, using these as the main control would require multiple applications over several months and this option will have a negative impact on insects other than Japanese beetles including beneficial insects and pollinators.

The main tactic recommended by those who want to avoid using insecticide sprays is to knock the Japanese beetles off the leaves of the plant into a container of soapy water below where they will drown. Although this tactic works on small garden plants and for a small infestation, it’s not a feasible option if they are eating your apple or cherry tree since you can’t reach the top, where they usually start feeding on a tree.  It’s also not very feasible if you have a major infestation. I can personally attest to a time when I had it on some hazelnut bushes and after knocking off the beetles into a bucket of soapy water 5 times in 1 day there were just as many at the end of the day on the bush as there were at the beginning.

There are other options for control that are less work and non toxic to beneficial insects like milky spore, a natural soil dwelling bacteria that can kill a significant amount of the Japanese beetle grubs in the soil before they emerge to eat your plants. This bacteria can be very effective at controlling Japanese beetles long term but can also have some problems. First it’s a long term tactic. If you have Japanese beetles feeding on your plants right now milky spore isn’t going to do anything to stop that. Also, it doesn’t control those flying in from neighboring properties as Japanese beetles can fly several hundred yards (1). This means for those in urban and suburban areas milky spore will only have limited success unless you get neighbors to join in. Those with large properties would typically have better success with milky spore but then there is the issue of cost. Although milky spore can remain effective for 10-20 years once applied, it can cost as much as $35 for enough to treat 2,500 square feet. So for a large property it can get costly. 

The ultimate control is if there could be an insect that naturally feeds on the Japanese beetle. In fact, two predatory insects that feed on Japanese beetles have been found and introduced to the United States for just such a use; Tiphia vernalis and Istocheta aldrichi. Tiphia vernalis has been found to parasitize up to 58% of Japanese beetle grubs killing them before they emerge. Istocheta aldrichi has been found to parasitize up to 20% of adult Japanese beetles killing them before they could lay eggs. So together they could theoretically reduce the Japanese beetle population by almost 70% (2,3).  Alas, although these have been introduced and established in the United States neither have made it to the St. Louis region yet and you can not purchase them yourself. So for now we will just have to hope they make it here one day.

So then again the question is what option is there if you don’t want to use insecticides, have a large infestation, and milky spore isn’t feasible for you? The answer to that question is the much maligned Japanese beetle trap.  

No, not those little flimsy ones with the small bag that they sell at most hardware stores in the summer. I’m talking about a big mass trap. Many say never use the traps because they attract more to your yard then they catch. This is true if the trap is too small (as most of those bag traps are) or are not used correctly, but if used properly studies have found they can reduce the numbers to the point that they are not an issue. One study even found a 97% reduction in Japanese beetle feeding on the plants they were trying to protect (4,5).  

Japanese beetle trap attached to a 5 gallon bucket lid for mass trapping
Japanese beetle trap attached to a 5 gallon bucket lid for mass trapping

The disconnect between these studies that find them to be effective and many people’s personal experience saying they are not effective seems to be trap size and placement. The problem is that many put the traps by the plant they are trying to protect. Then because they only have one or two traps and the trap has a small bag, it will fill up in a day or sometimes even a couple hours. What this means is that you are putting something that attracts Japanese beetles right next to the thing they are already attracted to and like to eat. So if they are flying toward the trap and run into the plant first they are going to eat that plant. Many will still be caught in the trap when you place it by the plant you are trying to protect. But, as soon as the trap is full they will fly on over and eat your plant you so kindly lured them to. So unless these traps are being emptied often so that they are never full, than they are certainly bringing more to the area than they capture.

The University of Missouri and Lincoln University have found two things that are key to making the traps effective. What they say is that you must make sure you have a large container to trap the beetles in. The second important step is to not put it by the plants but instead, around the perimeter of the area you are trying to protect. You also want to make sure that the traps are spaced no further than 200 feet apart so that you have a continuous perimeter of the lure scent to attract the beetles. By placing them in a perimeter around your property it means that Japanese beetles emerging from the soil are attracted to the edge of your property instead of towards the plants you are trying to protect. Also, those flying in from neighboring properties are intercepted and trapped before they get to your plants. If you have a relatively small property, such as a regular city lot, with the 200 foot spacing you may only need one or two traps. You would place the traps on either end of your property and or the place farthest from the things you are trying to protect. Having a large container to hold the beetles that fall in the trap helps deal with the issue of them filling up too fast and makes it more feasible to empty the containers as needed. Or if you use a really big container you might only need to empty it at the end of the Japanese beetle season.

Large trashcan mass trap.  These generally only need to be emptied at the end of the Japanese beetle season.
Large trashcan mass trap.  These generally only need to be emptied at the end of the Japanese beetle season.

When they need to be emptied there are a few tips to keep in mind. When you empty the container it is best to dump it into a container of soapy water to drown any that are still alive. It is also best to empty the traps before 9:00 am or after 6:00 pm because they fly during the day. Before or after those times they rarely fly, which makes it much easier to empty the traps. Once the Japanese beetles are all dead you can then decide what to do with all that organic matter.  They can be put in your compost bin or just pour them on the ground at the base of your fruit trees. If you then put wood chips or other organic matter over them they will compost nicely and the bugs that were eating your fruit trees are now fertilizing your fruit trees. It is important to know though, that because they are very high in nitrogen that they smell pretty strongly once they are dead. So if you find the smell to be a problem, covering them with wood chips or throwing them away might be your best option.

Lincoln University made instructions on how to make a mass trap like the trap described here. You can find the instructions to make your own here. These instructions show attaching the trap to a large outdoor trash can but you can use any lidded container. We have had success with lidded 3 and 5 gallon buckets. These smaller containers are much easier to empty, move around, and store when not in use but need to be emptied more frequently. Our adapted instructions using a smaller container can be found here. If you would like to make your own, you can buy the tops to the traps at our store online for pickup. We also sell the dual lures which are the most effective lures for trapping Japanese beetles and are rarely sold in stores. These are great if you want to make your own traps and in future years you will be able to reuse the trap you made and just have to buy the lures. 

Japanese beetle attracting dual lures
Japanese beetle attracting dual lures

It is also important to note that for best results the traps should be put out as soon as you first notice the first Japanese beetle. Although the traps are really good at intercepting Japanese beetles it’s harder to entice them off of something they are already feeding on. So if you have plants that are heavily infested with Japanese beetles the best option is to place your traps and then either remove the Japanese beetles by hand or by knocking them into soapy water or by using an organic insecticide like spinosad. If you have to use the insecticide, as long as the traps are already placed you should only have to use it once.


  1. https://www.aphis.usda.gov/plant_health/plant_pest_info/jb/downloads/JBhandbook.pdf
  2. https://bioone.org/journals/florida-entomologist/volume-90/issue-4/0015-4040(2007)90%5b780%3aSOTVHT%5d2.0.CO%3b2/Survey-of-Tiphia-Vernalis-Hymenoptera–Tiphiidae-a-Parasitoid-Wasp/10.1653/0015-4040(2007)90[780:SOTVHT]2.0.CO;2.full
  3. https://blog.uvm.edu/hoppenin/2014/07/28/having-trouble-with-japanese-beetles/
  4. https://pdfs.semanticscholar.org/797e/3744a3bbdebb7a31404924d94f9990bd9cf8.pdf
  5. https://www.greatplainsgrowersconference.org/uploads/2/9/1/4/29140369/organic_management_options_for_japanese_beetles_.pdf
  6. https://www.researchgate.net/publication/270341993_Mass_trapping_a_potential_organic_management_option_for_Japanese_beetles

Statement From Gateway Greening

Gateway Greening continues to be deeply saddened by the effects of police brutality in our communities, both locally and nationally. We have been taking this time to reflect on our organization’s role in the Black Lives Matter movement. We pledge to continue to use our social media as a space for these conversations and to do our part to keep the movement alive until change happens. We are following the leadership provided by Forward Through Ferguson during this time, and encourage all to see the resources and goals they have laid out.

Police brutality is a symptom of systemic racism in this country, as is access to education, healthcare, and food. Within our mission, we aim to educate and empower people to strengthen their communities through gardening and urban agriculture. Part of this mission includes fighting the systemic inequalities that keep communities from accessing fresh food, culturally important food, and making autonomous food choices.  Now, more than ever, people need resources to help them grow food for themselves and others.  During the height of the growing season, we believe we would be doing a disservice to the communities we serve by not providing the resources we have promised to deliver. At the same time, we cannot resume gardening content posts without acknowledging the shift, and without delivering the promise that we will continue to share anti-racist material.  

We also want to address the questions about our action steps moving forward. This movement has been impactful on our organization, and has come during a time when we are going through internal changes. In order to make sure our action steps are as carefully thought out and as impactful as possible, we have been taking time to reflect, organize, and question what these steps will look like for Gateway Greening. This has and will continue to take time, but by putting in the work now, we will create lasting progress in our services and the communities we serve. We will be releasing our action steps soon, and appreciate everyone’s patience. 

Thank you to the organizations in St. Louis who have been working hard to lift voices of color and bring attention to the Black Lives Matter movement. Thank you to Forward Through Ferguson for providing clear action steps. Thank you to the individuals who have shared their stories and hardships during these times. Together we can enact change and carry the movement forward.  

Processing Rice

by Dean Gunderson

This is the second Part of our series on growing and processing rice.  To learn how to grow your own rice check out our blog post on it here.

So the rice is grown, the plants are harvested and have been dried, but now what?  How is this dried grass plant turned into a bowl of delicious cooked rice? Well with the right tools, the right know-how, and a little bit of elbow grease it’s possible to grow rice starting from seed and ending in any rice dish desired.

Fully dried rice bundles ready for processing
Fully dried rice bundles ready for processing

When it comes to processing rice there are three main steps.  In order, those steps are to thresh the rice, dehull the rice, and finally to winnow the rice. Threshing is the process of removing the seeds (the grain) from the rest of the plant (the straw).  Dehulling is taking the hull, which is the papery straw-colored covering that surrounds each individual rice seed, off of the grain. Winnowing is separating out the grain from the chaff, which is the name for the hull once it’s been removed from the grain.  So let’s start at the beginning.

All that’s required to thresh grain is a little force.  There are many ways to thresh rice but probably the easiest way for garden scale production is the trash can method.  For this all that is needed is a trash can or some other large container. Grab a small bundle of dried rice plants and hold them about halfway up the stalk with the top of the plant, where all the seeds are, inside the trash can.  Then vigorously move the bundle of rice back and forth hitting the inside walls of the trashcan until the grains have been knocked off into the trash can. After doing a couple of bundles you will get a feel for how fast to move the bundle and how much force to hit the sides with.  It does require a fair amount of force so don’t be timid about it.

Image showing two bundles of rice.  One before and the other after threshing using the trash can method.

Rice bundle before (left) and after (right) threshing using the trash can method

There are plenty of other ways to thresh rice that can be tried if desired.  One way is to cut a length of old garden hose and while holding the rice inside a trash can beat the seeds with the piece of hose to knock them off.  Just beating the plants on the ground is another easy way to do it and the main way people have threshed grain since the beginning of agriculture. The main downside to this method is the seeds will often go flying and make a mess.  Another way that is particularly fun if working with kids is to put the dried plants on a tarp and cover them with another tarp or the other side of the same tarp. Then have the kids walk or stomp all over the plants. This force will knock the seeds off the stalks.  The main downside to this is that it takes more work to separate the seeds from all the straw.

Now to the hulling.  Hulling requires the twisting, rubbing, or grinding of the seed with just enough force to rub the papery hull off but not grind the grain into flour.  There are theoretically ways to do this without anything special and there are a lot of ideas on how to do this online. The internet suggests everything from rubbing it between the palms of the hands, laying the seeds on the table and rubbing them with a cutting board, twisting them on the ground under foot, a mortar and pestle, and on and on.  We feel comfortable saying that all of these techniques are great and will work fine……if the goal is to eat a tablespoon of rice. Staff and Gateway Elementary students tried all these ideas. Even energetic kindergarteners stomping on the rice yielded only a small cup of rice. 

Students helping to thresh rice by jumping on it sandwiched between two tarps
Students helping to hull rice by jumping on it sandwiched between two tarps

Luckily one of our AmeriCORP VISTAs Evelyn, was able to find a solution.  She was able to design, build, and write instructions on how to make a simple but really effective hand crank rice dehuller out of a cheap grain grinder, some rubber, and glue, for less than $30. So have a look here, do yourself a favor, and just build one of these, it’s pretty simple. 

Using the DIY grain dehuller

If you have any questions we are happy to help. The building instructions also have detailed instructions on how to use it. Essentially though it works by putting the unhulled rice in the top and cranking the handle until it all comes out and then run the same rice through again two more times and it is all dehulled and ready for the final step.

Now the last step is winnowing the grain from the chaff, which is just cleaning the grain.  Chaff is very light and airy whereas the grain is relatively heavy. So the chaff just needs to be blown off.  There are two main ways of doing this and which method to use is up to personal preference and the quantity of grain to be winnowed.  If there is only a cup or two of dehulled rice the easiest way is usually to put it in a big bowl. Take the bowl of rice and chaff outside and while constantly swirling it inside the bowl forcefully blow into the bowl.  The chaff will blow up and out and the heavier grain will remain. Keep doing this until all the chaff is gone.

Dehulled rice ready to be winnowed
Dehulled rice ready to be winnowed

The other method is the most common method and the best if there is more than a cup or two.  This method requires two large containers and a breezy day. Although it’s best to do this outside because it can get messy if you want to do it inside a fan can replace the wind.  Hold the container with the rice and chaff about 18” or so above the empty container, which should be sitting on the ground, and slowly pour it into the empty container. The heavy rice grains will drop into the container but the lighter chaff will get carried away by the breeze.  Keep pouring the rice and chaff mixture from one container to the next, increasing the distance between the two as you feel comfortable. Then once the chaff is blown off all that will be left is the ready to cook rice.

Now also don’t forget to use all that straw and chaff from the rice processing.  The straw and chaff are great mulches for the garden, suppressing weeds and conserving moisture in garden beds.  In addition to its use as mulch, the chaff can also be used to make seed starting mix, which is used to start seeds indoors.  Mix 1 part rice chaff with 2 parts coco coir, which is a waste product of coconut farming, to make a good, sustainable seed starting mix. 

I forgot, there is actually one more step left to process the rice, the most important step!  Now it’s time to cook and eat some homegrown and processed St. Louis rice. Enjoy!

Central Asia Regional Bed Varieties: by Cameron Lee

Take an Agricultural Tour of the World with Gateway Greening!  For the next few weeks, we’ll be posting a new blog post each Monday highlighting a regional bed from our Demonstration Garden. While these posts will not include growing instructions, they will be history lessons on the agricultural practices of regions around the world.

One of our regional raised beds in the Demonstration Garden this year is growing plants that were originally domesticated in Central Asia. While many people often overlook this region, some of the world’s most common foods are native to the area.  Even something that many consider being uniquely American, such as apple pie, can trace its roots back to Central Asia. The region is unique in that it served as a confluence of culture between Europe and Africa to East Asia and India. Perhaps best known for Marco Polo’s journey on the Silk Road, the geographical location of Central Asia allowed the exchange of ideas, commodities, and luxury goods to travel between Europe and Asia. Stretching from the Caspian Sea in the West to China in the east, from Afghanistan in the south to Russia in the North, this region has a fascinating history where great empires rose and fell. This region includes the modern-day countries of Kazakhstan, Uzbekistan, Kyrgyzstan, Tajikistan, Turkmenistan, and Afghanistan. Home to a wide array of varied geography, like the high passes and mountains of the Tian Shan, the vast deserts of Kyzyl Kum and the Taklamakan, and especially the seemingly unending treeless, grassy steppes.

Zhongar-Alatau national park in eastern Kazahstan, which contains stands of the wild ancestors of several domesticated fruit species.  The most famous of which are the stands of the wild ancestors of the domesticated apple. Some can be seen at the bottom and right corner of this picture.

This vast region contains picturesque landscapes that played a significant role in shaping human history. Countless trading caravans, herders, soldiers, and artisans all traveled along a series of trade routes that later came to be collectively known as the Silk Road. The resulting economic traffic through the region gave rise to the legendary Silk Road cities of Bukhara, Khiva, Loulan, and Samarkand. It is important to note that the “Silk Road” was not a road by modern standards, nor was silk the only commodity. It was a cultural and economic phenomenon of exchange and interaction that helped shape the world as we see today. The prehistoric Central Asians connected the corners of the ancient world and helped to spread innovations across the continent. While silk was by far the most valuable luxury commodity traded, goods like precious gemstones and minerals, luxury goods, spices, domesticated crops and animals, ideas, and technology were all exchanged throughout the ancient world. The dispersal of crops and animals remained unmatched until the Colonial era. Crops like wheat and millet traveled along the Silk Road, with millet becoming the summer crop of the Persian Empire and adopted by the common people of Rome and wheat to Han China, grown during the winter season, was transformed to make noodles and dumpling skins. The movement of domesticates saw a change in culinary traditions, gave rise to crop rotation cycles, as well as globalizing regional cuisines. 

While Central Asia is seemingly a vast, desolate expanse today, parts of it were considered to be gardens of Eden for millennia. Until the first millennium BC, much of southern Central Asia was a lush expanse of short shrubby forests, which included wild cultivars of pistachio, almond, cherry, and English walnut trees. The mountainous regions were once covered by sea buckthorn, Russian olives, wild apples, hawthorn, mountain ash, and a wide variety of nut-bearing trees. While much of these forests are gone today, there are still small, vibrant pockets of agricultural land that continues to produce fruits including grapes, pomegranates, and sweet melons. The Memoirs of Babur or Bāburnāma, compiled between 1483 and 1530, chronicles the travels of Ẓahīr-ud-Dīn Muhammad Bābur, including his observation: 

“Grapes, melons, apples, and pomegranates, all fruits, indeed, are good in Samarkand; two are famous, its apple and its grape. Its winter is mightily cold; snow falls but not so much as in Kabul (Afghanistan); in the heat, its climate is good but not so good as Kabul’s.”

During Bābur’s time, Samarkand was the capital city of the empire of Timur. Set by a fertile oasis watered by the Zarafshan river, the city was the center of education and commerce. In the heart of the city, Timur and his successors constructed the Rēgistan, an Islamic university that rivaled the grandness of European palaces. 

Although many would influence Central Asia, the introduction of Islam had the most significant impact on the region. In 751 CE, the Abbasid Caliphate along with their ally the Tibetan Empire fought against the Chinese Tang Dynasty in order to control the Syr Darya region. Fought at the Talas River, the battle resulted in the Islamization of Central Asia. The Islamization of Central Asia has had profound impacts on the region, with the adoption or blending of the Islamic religion into native cultures. During this time the cities of Samarkand, Bukhara, and Urgench prospered and were centers of Islamic learning, culture, and art in Central Asia. Though the Mongol invasion in the thirteenth century would slow the process, Islam remains the dominant religion in the region today. 

The adoption of Islamic architecture also led to the construction of ornate Persianate gardens and orchards, with the crops irrigated using a complex system of conduits. Perhaps the most significant achievements of the Qarakhanid period (840-1212 CE), was the development of elaborate irrigation systems and expanding cultivated farming land into the deserts, even digging a one-hundred kilometer (sixty-two mile) canal connecting the Taraz region of southern Kazakhstan to the Ferghana lowlands in Uzbekistan. The agricultural practices of the region following the Mongolian conquests were preserved in Persian agricultural manuals, such as the Irshad al-Zira’a (guide to agriculture) composed in 1515 in Herat, Afghanistan by Qasim B. Yusuf Abu Nasri Harawi. The book discusses irrigated gardens and elaborate pavilions, going in-depth about the cultivation of wheat, barley, millet, rice, lentils, and chickpeas; viticulture; garden crops, including cucumbers, lettuce, spinach, radishes, onions, garlic, beets, and eggplant; herbs and aromatic plants; fruits and nuts including, melons, pomegranates, quinces, pears, apples, apricots, plums, cherries, figs, mulberries, and pistachios. The prominence of rice is also attributed to the period. These gardens and orchards were later expanded upon, under the stewardship of the tenth-century Qarakhanid ruler Ibrahim ibn Nasr. Large-scale game and hunting preserves were created. The gardens and orchards were well-maintained, in fact, Suzani Samarkandi, the only poet of the Qarakhanid court whose writing survives today, stated that Samarkand was “a paradise on Earth.” 

Central Asia was a critical region in shaping world history. The cultural effects from the region still affects us today. The Silk Road revolutionized agricultural practices, changed culinary traditions, and saw the spread of innovation across the ancient and medieval world. Highly lucrative, any empire that held control over parts of the Silk Road often experienced economic advantages. One of the largest empires in history, the Roman Empire even benefitted from the Silk Road. By enacting tariffs and taxing commodities arriving from the east, Rome was able to experience unprecedented economic growth. According to Pliny the Elder, advisor to Emperor Vespasian, estimated that more than 100 million sesterces of bullion left the empire as a consequence of the international commerce. Giving Rome the economic power to fund their wars and become an ancient superpower.

Beckwith, Christopher I. Empires of the Silk Road: A History of Central Eurasia from the Bronze Age to the Present. Princeton, NJ: Princeton Univ. Press, 2011.

Choi, Charles Q. “Silk Road Travelers’ Ancient Knowledge May Have Irrigated Desert.” LiveScience. January 12, 2018. Accessed August 23, 2019. https://www.livescience.com/61408-silk-road-helped-irrigate-desert.html.

McLaughlin, Raoul. The Roman Empire and the Silk Routes: The Ancient World Economy & the Empires of Parthia, Central Asia & Han China. Pen and Sword, 2016.

Spengler, Robert N. Fruit from the Sands: The Silk Road Origins of the Foods We Eat. Oakland, CA: University of California Press, 2019.

Stevens, Chris J., Charlene Murphy, Rebecca Roberts, Leilani Lucas, Fabio Silva, and Dorian Q. Fuller. “Between China and South Asia: A Middle Asian Corridor of Crop Dispersal and Agricultural Innovation in the Bronze Age – Chris J Stevens, Charlene Murphy, Rebecca Roberts, Leilani Lucas, Fabio Silva, Dorian Q Fuller, 2016.” SAGE Journals. June 1, 2016. Accessed August 23, 2019. https://journals.sagepub.com/doi/full/10.1177/0959683616650268.

Mesoamerican Regional Bed: by Cameron Lee

Take an Agricultural Tour of the World with Gateway Greening!  For the next few weeks, we’ll be posting a new blog post each Monday highlighting a regional bed from our Demonstration Garden. While these posts will not include growing instructions, they will be history lessons on the agricultural practices of regions around the world.

Similarly to the Andes Mountains in South America, Mesoamerica developed their form of intensive agriculture throughout the Valley of Mexico. Built by the Aztecs, chinampas are a form of intensive agriculture that was carried out on a large scale in and around Lake Texcoco. Aztec engineers artificially constructed small rectangular shaped areas of fertile arable land to grow crops on the shallow lakebeds. These floating lakebeds were referred to as “floating gardens” by the Spanish conquistadors, primarily centered around the lakes Xochimilco and Chalco. Near the natural springs that flow alongside the south shore of the lakes. The Aztecs cultivated maize, beans, squash, amaranth, tomatoes, chilies, and a diverse array of flowers, which were prevalent in Mesoamerican festivals and feasts. The fields surrounding the imperial capital of Tenochtitlan were estimated to have provided enough food to feed at least one-half to two-thirds of the populace of the city. 

Map showing Tenochtitlan, the capital city of the Aztecs and the lakes of the Mexico Valley showing the locations of the Chinampas.

The majority of farming in the forested areas of Mesoamerica was conducted using slash and burn agriculture. By using this particular method, the chinampas were fertilized by cutting and burning the vegetation to clear ground. Fernando de Oviedo’s description of “slash and burn farming” stated, “The Indians first cut down the cane and trees where they wish to plant it… After the trees and cane have been felled and the field grubbed, the land is burned over, and the ashes are left as dressing for the soil, and this is much better than if the land were fertilized.” (Fernandez de Oviedo 1969 [1535]: 13-14). The initial preparation of agricultural plots was followed by the construction of small earthen mounds or platforms, that measured one foot high and three to four feet in diameter in some areas. Mounds on which they grew their crops on. Their fields or “conucos” consisted of a series of small circular earthen mounds, on which a variety of plants were grown. This method of farming would spread into what is now the United States. Roughly two centuries later, English and French explorers encountered the Iroquois who practiced a similar approach, cultivating the “Three Sisters,” maize, beans, and squash which grew on similarly constructed large earthen mounds.

The Maya would also develop raised field systems near the Candelaria River. At first, the Spanish Conquistadors did not recognize the significance of the fields. However, it would be noticed by the chronicler Francisco Lopez de Gomara who informed General Cortes in 1519 that the Mayan agricultural fields; “both worked and in fallow…” [are] “difficult to cross… [that those on foot could], “walk on a straight line, crossing ditches at each step.” On the Gulf Coast, the Cempoalans constructed a series of aqueducts that flowed from the river into storage tanks or cisterns. From these storage facilities, water was then channeled to other cisterns through the aqueducts until finally emptying into the canals.

Some of the few remaining chinampas

While maize played a significant role in these pre-Columbian societies, cacao and vanilla beans were also important, serving as an important commercial crop during the pre and post-contact times. Cacao and vanilla beans served as forms of currency, while other major commercial crops like beans, manioc, and squash were commonly featured in their diets. 

Corn, beans, and squash as grown in a traditional Mesoamerican agricultural system

The arrival of the Europeans also brought with them their dietary categories, either intentionally or subconsciously, imposed their food and cuisines to the New World. While crops like maize were likened to wheat, many of the traditional Mesoamerican foods and processes were alien and at times revolting to European tastes. Particularly the insect-based or rotten foods such as, “large fat spiders, white worms that breed in rotten wood, and other decayed objects: did not resonate with established European tastes, despite the fact that rotten foods such as aged cheese, pickled fruits, and aged smoked meat were essential components of Western diets. When Columbus first encountered the Taino tribes he established relatively friendly terms; the “other decayed objects” included a specialty-zamia bread, which was manufactured from a species of cycad, made by grating the zamia root and then shaping the grated pulp into balls. After leaving them in the sun for two or three days to ferment, they turned black in color and wormy. When ripe, the zamia balls were then flattened into cakes and then baked over a fire on a griddle. The Tainos informed the Spaniard if it is eaten before it was black of not full of worms, then the eater would die. Zamia pulp unless fermented or thoroughly washed may be highly toxic. The societies of Mesoamerica had and still has, a long tradition of eating plump insects and algae that were plentiful in their environment. The maguey worm or the chinicuiles was a delicacy much favored by the Aztec court and still is a delicacy today. One dish that was more tolerable to the Spaniards was a bread made from the toxic yuca plant. Manioc roots were peeled and grated, and the juices were squeezed out under heavy pressure. When boiled, it was used to make a harmless cassareep sauce, which then can be transformed into tapioca. The Spaniards enthusiastically adopted cassava; in some accounts even claiming it as being superior to wheaten bread. 

Crops like maize had significant religious importance to the pre-Columbian societies, noting that shamans still use kernels to interpret omens. Its ancient divinity is evident by its iconographic and hieroglyphic association with primary deities and origin myths. According to iconographic interpretations on Classic Maya stelae and architecture suggested that the maize god was the “first father” and the Quiche Maya term Qanan or maize meant “Our Mother.” In the Mayan creation story known as Popol Vuh, it states that the gods used maize from the Mountain of Sustenance at Paxil Cayola as the main ingredient for the design of humankind. The mountain was filled with, pataxte (similar to cacao), cacao, zapotes (soft edible fruit), annonas (from the sugar apple family), jocotes (plum-like fruit), honey, and most importantly, yellow and white ears of maize. According to the creation story, Xmukane ground white and yellow kernels of maize that was provided by the Mountain of Sustenance. Modern Maya believes that eating maize offers a means of incorporating the divine or their ancestral flesh into their bodies allowing access to their ancestral language and esoteric knowledge regarding the spiritual realm. 

“Mesoamerica.” MesoAmerica. Accessed August 21, 2019. https://laulima.hawaii.edu/access/content/user/millerg/ANTH_151/Anth151Unit3/MesoAmerica.html.

“Pre-Columbian Civilization.” Pre-Columbian Civilization. Accessed August 21, 2019. https://www.newworldencyclopedia.org/entry/Pre-Columbian_Civilization.

Staller, John, and Michael Carrasco. Pre-Columbian Foodways Interdisciplinary Approaches to Food, Culture, and Markets in Ancient Mesoamerica. New York, NY: Springer New York, 2010.

Andes/South American Regional Bed Varieties: by Cameron Lee

Take an Agricultural Tour of the World with Gateway Greening!  For the next few weeks, we’ll be posting a new blog post each Monday highlighting a regional bed from our Demonstration Garden. While these posts will not include growing instructions, they will be history lessons on the agricultural practices of regions around the world.

Some of the plants growing in the demonstration garden this year are native to the Andes and South America which have been cultivated by indigenous peoples for thousands of years. These indigenous peoples included the Chibchas, Quechuas, Tairona, and Aymara peoples. Each had their lasting legacy that is still seen today. Recent archaeological finds and research shows that the pre-European contact civilizations in South America were a lot more advanced Europeans believed them to be. Each of these pre-contact civilizations was independently established and developed permanent or urban settlements, agriculture, civic and monumental architecture and followed complex societal hierarchies. Many of whom collapsed by the time of the arrival of the first permanent European colonists who reached the Americas. When the European explorers arrived in the New World, both native and European accounts state that the “New World” civilizations possessed many impressive feats. Such as having the most populous city in the world as well as modern theories of astronomy and mathematics. 

The history of the native peoples in South America begins with an Asiatic migration over the Bering Land Bridge, now known as the Bering Strait. Throughout millennia, people spread across all over the continent. These early peoples would form the first complex civilizations on the continent– the earliest being estimated to emerge around 5,000 BCE. The first inhabitants were hunter-gatherers and lived in local hegemonies throughout the Americas. In South America in particular, people spread over parts of modern-day Ecuador, Peru, Bolivia, Chile, and Argentina.

The terraces of the Andes mountains that still stand today that some are reviving the use of due to their efficiency and adaptability

The first evidence of agricultural practices in South America dates back to 5600 BCE, from the Norte Chico civilization. Considered the first complex society established in South America, they cultivated maize, potatoes, beans, avocados, among other native plants. To put this into context, the Norte Chico emerged around the same time the pyramids of Ancient Egypt were being built and predated the Mesoamerican Olmec by nearly two thousand years. They later significantly improved their agricultural practices with the construction of massive stone terraces in the high mountains of the Andes without beasts of burden or metal tools. The stone terraces not only extended the cultivated area, but also protected microclimates, allowing specific varieties to flourish. Archaeologists even suggest that an “amphitheater” found in the Cuzco region was an experimented field where the concentric terraces reproduced tiny variations in the upland environment. The Norte Chico can serve as a reminder that no one civilization can claim to have led the whole world and the human race in developing technology, culture, society, political organization, or religious belief.

These agricultural technologies and practices would be continued and expanded upon by the Incan Empire. They developed resilient breeds of crops that can thrive in harsh climates. They built cisterns and irrigation canals that lined mountains — further building more terraces into the hillsides, becoming progressively steeper. At the height of the Incan empire in the fifteenth century, the vast system of terraces, cisterns, and irrigation canals covered an area of an estimated one million hectares (just under four thousand square miles!) throughout Peru and was able to feed one of the most populous empires in the world of the time. However, these practices and traditions was lost to history when the Spanish Conquistadors invaded. The local populations were destroyed by war and disease; some researchers estimate as many as half of the total population perished following Spanish conquest. Though the methods may have been lost, remnants of the terraces remain. Inspired by recent archaeological research, people living in the Andes have made an effort to revive traditional crops and methods of planting. The reasons being that Incan agricultural techniques were extremely productive and more efficient in terms of water use than our current systems. Modern farmers have been looking at Incan ways that can offer simple, relatively easy solutions to help protect their communities, especially as climate change makes it more challenging to cultivate certain varieties of crops. 

The “amphitheater” that some believe was an experimental field designed to create many different microclimates for crops

The archaeologist Ann Kendall, in the late 1960s, discovered that the Incan stone terraces had several unexpected advantages. The stone retaining walls heated up during the day and slowly released the heat to the soil as temperatures plunged at night, keeping the plants’ roots warm during the often frosty nights and expanding the growing season. The terraces are also extremely efficient at conserving scarce water from rain or irrigation canals. Kendall said, “We’ve excavated terraces, for example, six months after they’ve been irrigated they’re still damp inside. So if you have a drought, they’re the best possible mechanism.” She also goes on to state that the Incan terraces are even today probably the most sophisticated in the world, building upon roughly 11,000 years of farming.

In addition to the agricultural advances being made in the Andean region there were also advances being made in the Amazon River basin by farmers in the rainforest.  Here they developed a way to enhance soil to create what is known as terra preta, a soil with a large amount of charcoal in it that is rich in nutrients and in university trials, has increased crop yields up to 800%. In addition to higher yields this soil can control water and reduces leaching of nutrients from the soil. Recent research conducted shows high levels of nitrogen, phosphorus, potassium, and calcium in the soil. We know that Terra Preta was a man made soil due to the discovery of unfired pottery in the soils, similar to the way modern gardeners add perlite or sand to potting mix. This serves as a way of keeping the soil from baking completely tight under the intense tropical sun before vegetation grew to cover the soil. The soil tends to be black or dark brown and the the way Terra Preta soil is made give it the ability to sequester carbon at such a high rate that it actually sequesters more carbon in its making than is used to make it, giving it the potential to help with the problem of climate change. The astonishing part is that this agricultural technology was made without modern science and was made by the early pre-Columbian South Americans; technology that was lost following the arrival of the Spanish Conquistadors. 

Though a lot of the traditions and cultural practices of these pre-Columbian South American civilizations would be largely lost, recent research and studies being conducted are revealing more information every day. Recent evidence suggests that the Norte Chico may have been the most densely populated area of the world at the time; the only exception could have been in northern China. Contrary to what was initially believed, many of these civilizations are what we consider advanced civilizations, which challenges much of what is left out of our history textbooks taught in schools today. 

Winklerprins, Antoinette. “Terra Preta.” The Soil Underfoot, 2014, 235-46. Accessed July 30, 2019. doi:10.1201/b16856-22.

Erickson, Clark L. “Raised Field Agriculture In the Lake Titicaca Basin.” Expedition30, no. 3. Accessed July 30, 2019. https://www.sas.upenn.edu/~cerickso/articles/Exped.pdf.

“Pre-Columbian Civilization.” Pre-Columbian Civilization. Accessed July 18, 2019. https://www.newworldencyclopedia.org/entry/Pre-Columbian_Civilization.

Smith, Michael E., and Katharina J. Schreiber. “New World States and Empires: Economic and Social Organization.” Journal of Archaeological Research 13, no. 3 (September 2005). doi:10.1007/s10814-005-3106-3

Jordan, David K. “Chronological Table of Mesoamerican Archaeology.” Jordan: Mesoamerican Chronology. April 04, 2019. Accessed July 18, 2019. http://pages.ucsd.edu/~dkjordan/arch/mexchron.html.

O’Brien, Patrick. (General Editor). Oxford Atlas of World History. New York: Oxford University Press, 2005. p. 25