How to Keep Gardens Alive in Intense Heat
Reading Time: 4 minutes
By Stacy Benjamin The weather is one of the most significant factors affecting the success of our gardens. In addition to planning your planting and harvest dates based on the average frost dates for your area and being aware of which areas of your garden receive full or partial sun, being prepared for hot weather extremes is another important consideration. Triple-digit temperatures can ruin months of hard work in a hurry! Planning ahead to keep our gardens alive in intense heat is increasingly necessary, with heat waves becoming more common.
Here are a few tips to help your garden survive the extreme summer temperatures.
Soil Preparation
Incorporating compost into your soil is one of the best things you can do to help soils retain moisture. Adding organic material improves the soil structure and its water-holding capability. It also adds nutrients to the soil and makes it easier for plant roots to access and absorb the moisture and nutrients they need. It’s best to add a few inches of organic material to your garden beds in the fall or early spring and give it a little time to settle and get incorporated into the soil before planting the garden. Soil preparation is not a one-anddone type of task. Building moisture-retentive and nutrient-rich soil is a process that should be considered ongoing, with additional organic material being added each year to continue improving the soil and replacing the nutrients used up each growing season.
Mulching
Mulching is a valuable tool to prevent moisture from evaporating from the ground surface and helps cool the upper few inches of the soil. There are many options for using organic materials, such as mulch, including several that you may already have on hand, like chopped leaves, grass clippings, straw, wood chips, and compost. Mulch should be applied to a depth of two to three inches, and it can be applied over the entire bed or just around individual plants. If using it around individual plants, be sure to apply it under the entire leaf canopy of the plant, which is a good indicator of the area of the root zone.
There are also inorganic materials that can be used as mulch, such as black plastic and landscape fabrics. These types of mulch have the added benefit of pulling double duty as a tough weed barrier. In addition, black plastic absorbs the heat of the sun and can warm the soil temperature a few degrees, which heat-loving plants may appreciate. While the cost or availability of the different types of mulch may be the determining factor for some, aesthetics may be another important consideration for other gardeners. Organic materials tend to look nicer than black plastic or landscape fabric, but both will get the job done.
The Right Plant in the Right Place
Knowing whether the vegetables you are growing prefer full sun or partial sun and planting them accordingly to get the right amount of sun will help them continue to thrive as the summers heat up. Plant heat loving-vegetables such as tomatoes, peppers, squash, and eggplant in the areas of your garden that receive the most sun, and you’ll likely find that the hottest summer days only make them happier. Plant leafy greens and vegetables known for bolting when the temperatures rise (such as lettuce, broccoli, and cauliflower) in areas that receive at least partial shade, and they will have a better chance of lasting a little longer into the growing season as the temperatures heat up.
More vegetable varieties are becoming available that are bred to be bolt-resistant, and these are an option to consider as summers get hotter. That being said, sometimes you just can’t fight Mother Nature, and there may be some vegetables that don’t pay to grow if they consistently fail to thrive during the hot weather. I personally decided not to grow broccoli this year because it bolts more often than not, even when I take precautions to prevent it.
Water Correctly
Watering slowly and deeply every few days is a more effective strategy than giving plants a quick sprinkle every day, which only moistens the soil surface. That being said, daily, deep watering is often necessary when the temperatures rise into the upper 90s or the 100s. Watering should be done during the cool part of the day so that the water has time to soak into the soil and be absorbed by the roots before the heat arrives.
This is especially important when very hot days are in the weather forecast. Get up early these days to get your watering done — your plants will appreciate it. If you have a big garden or don’t have the time to water plants deeply, consider installing soaker hoses or a drip irrigation system that will do the watering for you.
Don’t be surprised if some of your plants occasionally look wilted, even with correct watering and the use of mulch. Large-leaved plants such as squash and pumpkins tend to wilt on hot days when grown in full sun. The leaves should return to their normal appearance in the late afternoon when they get some relief from the direct sun. If leaves remain wilted in the morning and you have ruled out disease and insect damage as potential causes of wilting, then they are likely suffering from water stress and need more water.
Make Your Own Shade
Vegetables that prefer partial sun can be grown in the shade of taller vegetables. Corn or a trellis covered with pole beans can provide shade for crops that appreciate the shade, such as lettuce and other leafy greens. Vining vegetables such as cucumbers and squash can be grown on a trellis installed diagonally to the ground so there is space for growing shade-loving vegetables underneath.
Another way to help your plants survive intense heat is to hang shade cloth by draping it on top of hoops over a garden bed or by attaching it to garden stakes or fencing. Even a large patio or beach umbrella can be used to provide temporary shade. I’ve also used large cardboard boxes over shorter plants to shield them from the sun during heat waves.
Closing Thoughts
Many of the methods discussed above can and should be implemented even during typical weather conditions to help your garden thrive. Keep in mind that just using one or two of the measures above may not be enough to prevent sun damage during intense heat. A well-rounded approach to soil preparation, proper plant selection, location, and watering will give your garden the best chance of surviving extreme heat events.
Originally published in the May/June 2023 issue of Countryside and Small Stock Journal and regularly vetted for accuracy.