There are many reasons that plants can wilt. Heat (especially coupled with direct sunlight) is one. 99% of the time running for the watering can or hose is not the answer.
I know it’s always upsetting to see a plant wilt. I’ve seen it many times over 33 years and as much as I know “all will be well in the morning” — I still become concerned.
Plants That are Prone to Wilting in Heat
Certain plants are more prone to this than others. Hydrangeas are a perfect example. Their big leaves often wilt when the temperatures are extreme in the day, but recover to perfect condition during the night. (If it’s still wilted in the morning, you have another problem.)
A few days last week saw our wonderful cool spring temperatures soar to summer highs of almost 90. My large sedums (like sedum autumn joy, neon and matrona) showed signs immediately. So did the mums.
While other perennials around them were loving it, all the leaves of the sedums and mums that were in direct sunlight wilted. Although 90 degrees is not extreme heat by summer standards, these two plants had not had time to accustom themselves to this kind of heat so early in the spring.
When summer arrives and we go through this same thing — but with highs in the 90s — they’ll wilt again. But by morning they will look perfect.
This wilting is caused by the plant giving off more water than it can take up. There is plenty of water in the soil right now, but the plant just can’t take it up fast enough.
It’s especially disconcerting to see vegetable plants do this. I’m always concerned I’ll loose the precious fruit they’re giving me.
I find cucumbers are very prone to this. In last summers severe heat, even though they recovered by the morning, I did loose a small percentage of their fruit. The vines just were not able to take up enough water to sustain the fruit. (In my heavily mulched garden, plants have soil water available to them longer than a conventional garden.)
Squash is prone as well. But I’m never 100% sure if its just the heat or the squash vine borer. Until of course, it either makes a full recover or dies and I find the borer grub in the stem.
What Not To Do
- Don’t handle the plants while they’re wilted. You can easily damage them when they’re in this condition. It could hamper their ability to recover and make them more prone to insects and disease
- Don’t water unless you’re positive that’s the problem. (For example – even through weeks of drought conditions there’s soil water available to plants in my heavily mulched garden.) If you have the ability to water — and you’re sure that’s the problem —- water at soil level and do so without touching the wilted leaves of the plant. And water either very late in the evening or very early in the morning.
Best Anti-Heat Maneuvers
Your best anti-heat maneuvers are good basic gardening practices. These simple but important practices allow plants to better deal with any stress, including heat and drought.
- When preparing your garden bed, loosen the soil deeply so roots can penetrate and seek what they need including cooler temperatures.
- Make sure your soil is always rich in organic matter to supply nutrients your plants need as well as helping your soil be able to retain moisture.
- Mulching helps keep moisture in the soil. It keeps soil temperatures cooler and thus, prevents the sun from baking the plant roots. (When roots become too hot their activity slows and a stunted plant can result.)
An Additional Strategy
Some plants just take the heat better than others. If you’ve gardened any length of time, you’ve found this out through experience.
As you continue to improve and design your yard and gardens, make sure you create spots that offer you and at least some of your plants relief from the baking sun. Even some vegetable plants appreciate a little dappled shade in late afternoon.
Good gardening practices and thoughtful design using trees, bushes and/or vine covered arbors can make a difference in how the the heat effects your plants.
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