Growing Your Own Sweet Potato Slips Experiment Results

If you still have sweet potatoes saved from last year, a fun activity for March is starting your own sweet potato slips! Last year we did an experiment using three different soil materials. Here are our results!

Materials: Trays with drainage holes, sand, coconut coir, compost, grow lights, and heat mats.

1. Tray 1: Sand
2. Tray 2: Coconut Coir
3. Tray 3: Compost

We filled each tray with its soil material and then placed the sweet potatoes so that each potato was buried about halfway in the soil material. All three trays were then placed on a heat mat and under grow lights. This was done on march 6.

By March 20, we saw sprouts on Tray 1 (sand) and Tray 2 (coconut coir). Tray 3 (compost) quickly followed with sprouts within the week.

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As the sprouts grew, we noticed that in Tray 1 (sand) they were growing only very small leaves while tray 2 (coconut coir) and 3 (compost) had normal-sized leaves on their sprouts. We also noticed that the sand in Tray 1 dried out very quickly which could have been a contributing factor. The coconut coir in Tray 2 also dried out a little faster than the compost.

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On May 8 the sprouts were tall enough for our jars so we cut them at the base of the sprout and placed them in jars filled with water. (We probably could have done this a bit earlier since our sprouts got a little tall!) We did not do this with the sprouts from Tray 1 (sand) since they continued to have very small leaves.

Once we had cut the sprouts from the potatoes, we emptied the trays and put the potatoes in the compost pile. When we pulled the potatoes from the soil material we noticed that those from Tray 1 (sand) had very little, if any, roots! Potatoes from Tray 2 (coconut coir) and Tray 3 (compost) both had lots of roots coming from the sections of the potatoes that were under the soil.

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Within a couple of days, the sprouts in water had roots! It’s important to change the water often (every 2-3 days). Once they have a good amount of roots on them, and the temperature outside is warm, they are good to plant in the ground!

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All in all, we don’t recommend growing them in sand since they dried out very quickly. This would be especially important for teachers since they won’t be watered over the weekends. The compost was the best soil material but coconut coir also worked well!