Written by Meadowstone Place resident, Sandra B.

“We know that freezing weather affects our plants. What about this hot weather we have been experiencing lately? What effect does it have on our plants? And just how hot does it have to be to start feeling “hot” to our plants anyway? 100 degrees? Is that too hot for our plants? We know it’s too hot for we as people. Actually, the plants experience “hot” as anything over 85 degrees, so you know that the plants around here get a lot of exposure to hot this time of the year and for the many months ahead of us! Yes, it is at about 85 degrees that we need to start treating our plants with some special care to keep the heat from affecting them in bad ways. So just what are the bad effects that temperature can have on our plants and what can we do to help protect our plants from the damage that the heat can cause?

The actual damage that heat can cause depends upon a few things: now some plants can take high temperatures without any damage at all. Your cacti and the whole category of succulents are constructed with their thick skins instead of thin leaves to thrive in hot conditions so we don’t have to worry about them. They have adapted to live under hot conditions. But most other plants, particularly those with shallow roots like vegetables and annuals, and some perennials, especially those with large leaves, are particularly vulnerable. Plants with shallow roots are vulnerable because they will more quickly lose their access to water and plants with big leaves are more vulnerable because they will lose more water into the air through transpiration. We are beginning to see a pattern here I think. Water is a big factor when it comes to survival in the heat. And indeed it is. In fact these 2 factors – Heat and Water – are always combined when you are looking at the impact of heat on plants. The lack of water will intensify the effects of heat and in turn, the addition of water can help protect plants, to a degree, from the bad effects of heat. So we rarely talk about one of these without talking out the other as well. So keep that in mind.

So what are the bad effects of heat? That depends upon where your plant is in its development. If it is a seed trying to germinate, heat aids germination up to a point then above that point it stops helping and starts hurting. Each kind of seed has an optimal range for germination and it helps to know that to know when to plant it. Excess heat when a plant is developing its roots can cause a plant to develop stunted or abnormal roots and can cause a plant to fail. One effect that we often see is when vegetables are approaching harvest and the heat abruptly rises and the plants shoot up long stems and flowers – we call that “bolting” – and we know that there will be no more harvest this year. Tomato plants will stop producing when the temperature gets too high, usually in the mid to upper 90’s. Some plants will stop producing flowers when the temperatures get too high. The plant is doing this as an effort to save itself. Producing flowers or fruits is a luxury for a plant. It is the first function they will shed when they feel threatened, when they feel a need to concentrate their efforts on preserving what energy they have on basic survival. When temperatures get too high even the basic process of photosynthesis can get out of balance and then the plant’s survival will be in question.

So what can we do to help the plant along during these difficult times? Water, of course, is the main tool we have available to us to help support the plants. They need water at least once a day, some, especially plants in pots, may require watering twice a day. If plants are in pots and are in full sun, moving them to a shadier spot may provide some extra protection. Using mulch on the soil is a good way to conserve water in the soil. Make certain your plants have all the fertilizer they need to keep them strong and healthy and better able to stand up to the challenges posed by the weather. In some cases, providing shade in the form of a trellis or shade cloth will protect plants in full view of the direct sun.

We cannot control the weather, as we well know. All we can do is provide the best for our plants and hope the weather is moderate and our plants survive. What we can do for ourselves is stay inside where it is cool and take our walks in the morning or in the evening when the temperatures are more comfortable and hope for the occasional day when the temperature is in the upper 70’s and low 80’s and be glad we are not living in Houston with their humidity!”

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