Drive around your neighborhood on a hot summer day, and you'll see many approaches to watering plants. Some homeowners break out the hose at the end of the workday, while others program the automatic sprinklers to come on at dawn for 15 minutes a day. Others figure that the plants are getting a drink whenever the kids decide it's time to play in the sprinkler. However, timing irrigation will lead to healthier plants and it can also save on your water bill.
How to Water Plants in Summer
Watering plants in the summer can be an art. Too little or too much water isn't good for gardens. Seasoned gardeners follow this rule of thumb: Water deeply and less often rather than watering too little too often.
Evenly water your plants using tools like soaker hoses for beds and watering cans for containers to give them consistent moisture. Letting the soil slightly dry out before watering can promote growth. You must also apply fertilizer carefully during periods of high temperatures to avoid burning plants.
When to Water Plants During the Day
It's a good idea to administer water from an overhead device like a sprinkler or rain wand early in the morning. Watering at this time of day will allow foliage to dry quickly, which discourages fungal spores. But if you don't have time in the morning, it's perfectly acceptable to do evening watering. In the evening, just be mindful of watering more directly to the root zone rather than the leaves. Watering in the cooler evening can have its benefits, too, because the moisture won't evaporate so fast, giving it time to soak into the dirt.
Watering Annual and Perennial Plants
Whether your plants are annuals or perennials, try watering them in the morning during a heatwave. Morning watering gives the roots a good soaking and offers your plants enough moisture to get through the day without added stress. But during summer scorchers, you may need to water annuals and perennials more often.
Annuals are plants that finish their entire lifecycle in one growing season. This includes garden favorites like marigolds, impatiens, and pelargoniums. These plants have very shallow root systems and will suffer when the top few inches of soil dry out in the summer. You must water them frequently, even twice daily, when the mercury rises.
Perennial plants have deeper root systems that enable them to survive periods of drought from one season to the next. Some perennials, like butterfly weed and false indigo, have taproots that extend many inches into the soil, in effect tapping into water reserves during periods without rainfall. The best time to water perennial plants is once or twice a week, slowly and deeply so that the water does not run off before it has time to soak into the soil.
Containers dry out more quickly than garden beds, so it's best to increase watering in the summer. During heatwaves, water container plants twice a day, once in the morning to give plants a boost before the sun begins to bake down, and once in the evening to replenish what the day took away. However, the type of container can also affect watering frequency. For example, plastic and fiberglass pots are nonporous which means they'll hold moisture well, so you need to be aware of overwatering. On the other hand, terracotta clay pots are porous, breathable, and can insulate roots from heat, but soil can dry out quickly requiring more watering.
Dry vegetable gardens can lead to blossom drop, stunted vegetables, or even plant death. Vegetable gardens need deep watering at least two to three times a week and best in the mornings to keep the soil moist. Vegetable plants that may need extra water during heatwaves include cauliflower, celery, cucumbers, peppers, radishes, and squash. These plants demand consistently moist soil to produce the best crop. Use drip irrigation, or place a soaker hose at the base of your plants to avoid wetting leaves. If you must rely on sprinklers, water early in the morning to allow the sun to dry the foliage.
Trees and Shrubs
Passing rain showers can't give your trees and shrubs the adequate amount of water they need in the summer. Trees and shrubs need deep watering to encourage a healthy root system. Sometimes the best time to water them is right after a light rain to help the moisture sink into the soil. The time of day you water plantings isn't nearly as important as giving them a thorough soaking.
Follow this general watering guideline for trees and shrubs:
- Mature trees and shrubs: For a deep watering, place a hose at the base of a shrub or tree, and let the water run until the top 8 inches of the soil are moist. Do this every few days for established trees and shrubs.
- Shallow-rooted specimens: Hydrangeas, dogwoods, Japanese maples, and magnolias will need extra water—at least three times a week—to prevent dehydration.
- New plantings and transplants: Newly planted or transplanted specimens have small, still developing root systems that need encouragement to settle in. It can take at least two to three years before they are considered established. To encourage them, water deeply twice a week. Let the water soak into the soil which will stimulate the new roots to grow deeper into the soil.
How to Help Wilted Plants
When plants are wilted from lack of water, watering them should perk them back up quickly. However, other things can cause wilting, including pest and disease problems, and even overwatering (if the soil is moist and the plant is drooping, this could be the case). Furthermore, plants can wilt on a hot day as a way to conserve their energy to cope with the high temperature, but then rebound when the evening cools off. In time, you will get to know your plants and will recognize those that respond to heatwaves in this fashion.
Summer Watering Tips
- Plants absorb water through roots, not leaves, so you don't need to waste water on leaves that appear to be dry.
- To tell how deep the water is penetrating the soil, use a stiff metal rod. Push it into the soil after you water and it will stop when it hits dry dirt.
- Use a thin layer of mulch to help your plants conserve water during hot summers.
- Irrigate your garden with pure rainwater by setting up rain barrels near gutters and downspouts or installing a rain garden to collect runoff. Plants will thrive and it will reduce your water bill.
- Another way to conserve water is to bury unglazed clay pots in the ground and fill them with water. This ancient way of irrigation uses low-fired vessels, called ollas, to let water consistently seep through the clay walls to nearby plants and trees.
Consistent Watering Needed During Hot Weather Gardening. Illinois Extension
Watering the Vegetable Garden. University of Minnesota Extension