Three Ways to Help Your Garden the Heat

The heat has arrived. Every summer, we get this oppressive heat and humidity. It’s not enjoyable for us, and it’s also very stressful for plants. So we figured now would be a good time to discuss the best options to help your plants get through the heat of summer while still growing and producing a bountiful harvest for you and your community.

First, what is considered high heat? When we get to this time of year, it’s summer crops that you are growing, which are adapted to heat. But when you get into temperatures exceeding 86, especially when we get into the 90’s and above, it’s too hot for many plants, and they start shutting down. During photosynthesis, plants need to open up small holes in their leaves to let CO2 in. Doing this also lets moisture out of the plant. When temperatures get into the 90’s, plants start hitting an inflection point where the amount of water they lose to evaporation starts not being worth it for how much energy they can produce from photosynthesis, so they start limiting, or if temperatures get high enough, totally stopping photosynthesis. In this instance, they will photosynthesize in the morning and late evening when the temperatures drop, but that energy is mostly being used to repair damage done during the heat of the day. This means your plants have less total energy to grow food. So during this heat, you will notice slower growth, and in fruiting crops like tomatoes, you will see less fruit and/or fruit not ripening.

So how, then, do you deal with the heat? There are three main ways to help: proper watering, mulch, and shade cloth.

1. Proper watering goes a long way to helping your plants thrive in the heat. If they are short on water, they are more stressed, and they will slow down photosynthesis at lower temperatures than if they have enough. So, as usual, it’s best to check the soil, and if it is dry 1-2” down, then it’s time to water. It’s best to water early in the morning if you can, so the plants have water as they go into the heat and the leaves dry off, but making sure they get water is more important than getting the time perfect.

2. Mulch is another powerful tool in having a thriving garden in high heat. Mulch helps to retain moisture in the soil, which is helpful as we just discussed, but it also lowers soil temperature. Experiments in large row crops showed that soil temperatures were 8-10F cooler in fields with mulch on them. This significantly lower temperature can seriously reduce the heat stress on the plant.

3. Last is providing shade. During the summer months, the sun is very intense, and there is a lot of solar energy hitting each square foot of surface. So much, in fact, that it’s more than plants can even utilize. This means that providing some shade to plants will actually not reduce plant growth, and in the case of extreme heat, it can increase growth by lowering the temperature.  For your summer crops, a 30% shade cloth is the best option to lower temperatures while still allowing the maximum usable light through. It also makes being in your garden much nicer in the summer.