9 Tips for Protecting Plants When It's Hot Outside
The Heat Is On!
Make sure your plants survive the summer by protecting them from high temperatures and scorching rays.
Slow & Thorough Preemptive Watering
Begin watering your garden slowly and thoroughly days or even a week before hot weather hits.
Water your trees in the morning or, if you don't have time then, late at night, soaking the ground all around the trunk out to the drip line in order to saturate the root zone.
Water slowly & thoroughly.
Applying water to your garden too quickly will result in run-off, & that won't do your plants a bit of good.
Whether you use a sprinkler system, soaker hoses, drip irrigation or water jugs with holes in them, be sure to water your garden slowly so that the soil soaks up the moisture rather than shedding it.
You want to moisten not only the topsoil but also the root zone, that expanse of soil that extends a foot to 18 inches deep beneath the soil surface.
Check the moisture content of your soil.
How can you tell when you garden needs water?
Different types of soil take up and retain moisture differently. Sandy loam generally drains well, while clay soil holds onto the wet. Most soil, however, is a combination of materials. In other words, your soil probably isn't simply loam or clay or sand.
To make sure that you've watered thoroughly, in a way that will truly benefit your garden, get your hands dirty: stick your fingers down into the ground and check the soil's moisture content before you stop watering.
Another way to tell if your garden needs water? Look carefully at your plants. Are the leaves browned and/or curled? Is there leaf loss? Unfortunately, by the time that sort of damage shows, it may be too late to save some plants.
Last week, when the heat index in our area was at 105 every day, we lost a rosemary plant. By the time I noticed its dull color and curling leaves, no amount of water could save it. RIP R. officinalis!
How do you water your garden?
Water in the morning if you can.
Slow and thorough watering in the morning is best if you can manage it.
Watering in the morning conserves water. Ordinarily, it's cooler in the morning, and the soil is cool, too, so water won't quickly dissipate through evapotranspiration as it will during the heat of the day.
If temperatures are really up there even in the early hours, you may opt to spray water all over your plants, too, not just on their root zones. Even in a heat wave, however, I tend to avoid wetting the leaves of plants that I know are prone to mildew, including roses, black-eyed Susan and bee balm.
Should you water at night?
If you don't have time in the morning, then very late at night is the second best time to water. At night, I avoid overhead watering completely as the water tends to cling to stems and leaves longer before evaporating, providing the perfect hot, wet environment for fungus and mildew. Instead, I apply all the water to the root zones only.
Should you water in the heat of the day?
In extremely hot drought conditions, you may decide to overhead water again in the heat of the day. Doing so will lower the temperature in your garden and provide moisture for spiders and other beneficial life.
Protect the Soil with Mulch
Water and then apply mulch.
Because it helps soil retain moisture, mulch is one of the best ways to keep plants cool during a heat wave.
Before adding mulch to your bed, water your flowers thoroughly and then apply the appropriate thickness.
Light-colored mulch like straw does double duty, helping hold moisture and cooling the ground by reflecting the sun's rays. For garden vegetables, silver plastic mulch is another option, as are wet weeds.
Wet Weed Mulch
A master gardener in Calvert County, Maryland, shared her unique method of mulching on the University of Maryland's Extension website: applying wet weeds as mulch. (Warning: don't do this with weeds that are in flower or that are going to seed. You'll end up with a lot more weeds!)
After the thunderstorms that often accompany hot weather, she pulls weeds while they're still wet and piles them around the plants in her garden. The wet weeds add more water to the garden, act as a mulch to hold moisture in and eventually decompose, feeding the soil.
As they say, "It's all good!"
Perform Routine Garden Maintenance
Removing weeds and deadheading should continue even in hot weather. In fact, both are beneficial to your garden and will reduce plant stress.
Weeds not only take up nutrients that your flowers and vegetables could be using, but they also use precious moisture, so pull them up!
The easiest time to do so will most likely be in the morning when the ground is moist with dew.
Removing spent blooms will also reduce plant stress. In fact, hot weather is a good time to make up a morning bouquet of fresh blooms.
Provide Shade for Plants
Using covers to provide plants with shade is an option, but I find covers a lot of trouble and not all that effective.
I prefer using other plants to provide shade.
Together, a mix of short and tall plants creates a more moist environment, and ... it seems to work. (Shade is one of the many benefits of the Three Sisters method of planting, a centuries old practice common among Native Americans.)
The hottest days of summer are also a good time to move potted plants into shady locations under trees and shrubs or in your flowerbeds.
Give Non-Native Plants Special Care
Native plants generally have coping strategies that help them survive the particular area in which they are indigenous, so if your area regularly suffers from heat waves, your native plants will survive the hot, dry weather better than exotics.
Plants have various drought-coping traits. Perhaps their pores shut down so that they don't lose water through evapotranspiration (moisture loss through leaves). Or perhaps their leaves are silvery to reflect the sun's rays or fuzzy to provide shade and keep the plant cool.
Non-natives may not be drought tolerant, so you're going to have to provide them with water in order for them to survive a heat wave. As noted above, water the plants slowly and thoroughly so that the topsoil and the root zone are moistened. And check them frequently for signs of stress--curled leaves, burnt stems and leaves, leaf loss and dull leaf color.
Tough Plants Need Love, Too
Check Drought-Tolerant Plants for Stress
Tough, drought hardy plants may not wilt in a heat wave, but that doesn't mean they aren't suffering.
Check them for signs of stress, too. Are their leaves warm to the touch? Curled up? Have they developed a lackluster color? Warm, dull, curling leaves are all signs of stress.
Give the plants a good, slow drink of water early in the morning. Although you may have chosen drought-tolerant plants specifically so that you would not have to water them, sometimes, when the heat is extremely severe, you simply have to—if you want them all to survive.
Use a Water Delivery System
Drip irrigation is an efficient, water-conserving way to water to plants slowly and thoroughly.
In drip irrigation, plastic tubing is used to deliver water drop by drop to plants' root zones.
Most home gardeners probably don't have a drip irrigation setup for their vegetable plants—or even for their foundation plants—although installing drip irrigation for "permanent" features in the landscape (like shrubs and small trees) is becoming more common.
If you lose plants to drought each year or spend lots of money each year irrigating your plants, drip irrigation could save you money in the long run. It doesn't really cost that much—usually anywhere from 50¢ to a dollar per foot, and that includes all the parts that you need.
Homemade Drip Irrigation (It's not pretty, but it works.)
If even 1¢ per foot sounds like too much to pay for drip irrigation, then check out this essentially cost-free method of slowly delivering water to specific plants.
All you need are empty plastic jugs, something to punch holes with and water.
You'll need large jugs, such as gallon milk or vinegar jugs, about 3-4 of them per small tree or shrub.
You could also bury jugs with holes in them in your vegetable garden next to plants that require lots of water, like tomatoes.
Some gardeners bury empty jugs, leaving just the tops exposed and filling them with water several times per week in hot weather. Here's how it's done.
- First, clean the empty jugs thoroughly. Then use an awl or scissors to make a small hole near the bottom of each jug.
- Fill the jugs with water from your rain barrel, or stick your fingers over the small holes and fill the jugs with a hose.
- Finally, set the water-filled jugs around the base of thirsty trees or shrubs. The jugs will slowly leak water, delivering moisture to the root zones without causing run-off.
Although soaker hoses can't target specific trees and shrubs like drip irrigation can, they do deliver water slowly, eliminating runoff and providing moisture deep down into the soil. They're ideal for a vegetable garden or flowerbed where plants are ordinarily planted close together.
Made from recycled rubber, soaker hoses have small holes (pores, really) all along their length that slowly weep water.
Downspout, Rain Barrel, Soaker Hose Combination
If you're not capturing at least some of the water that your roof sheds during a rain, you're missing out on a great source of free water for your garden.
My husband and I recently added another rain barrel to our garden. This one we attached to a downspout and a soaker hose, and it's made watering at least one small section of our flowerbeds much easier during the heat waves.
Soaker hoses can be buried in mulch or soil and left in place year round.
Burying soaker hoses is a good idea for several reasons. It will prevent water loss due to evaporation in extremely hot weather.
A buried soaker hose is also more inconspicuous than one that rests on top of the ground, and burying it gets the water closer to where you want it to be (the soil) so there's less likelihood of run-off.
Pro Tip Recap
- Stay apprised of local weather predictions so you can water thoroughly prior to a heat wave.
- Water early in the morning if possible.
- Water slowly and thoroughly in order to wet not only the topsoil, but also the root zone, encouraging roots to grow deep.
- When applying mulch to conserve moisture, water the ground thoroughly first.
- Perform garden maintenance like weeding even when it's hot.
- Plant heat sensitive plants in the shade of other plants, and move potted plants into the shade or indoors in the afternoon.
- Use a water delivery method that is easy for you to implement and appropriate for your budget.
- Give special care to non-native plants.
- Also check drought-tolerant plants and trees for stress. When the heat is extreme, they may need water, too.
Why Do Some Plants Wilt after Watering?
Sometimes, plants will wilt on a hot day even if you've watered them.
I notice this phenomena with our Shasta daisies. The problem, I discovered, isn't a lack of water in the soil; it's the plant's inability to take up water as quickly as it needs to in order to replenish moisture lost during evapotranspiration.
When the sun starts going down and the water loss through the leaves begins to lessen, the plant will perk up again.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2013 Jill Spencer