During droughts it's especially important to make every drop count, but even during more "normal" summer weather, it still makes sense to conserve this precious resource. There's a wealth of watering information out there, some fact, some fiction. Here are five common myths:
Myth: Plants need 1 inch of water per week
This often-cited figure doesn't take into account that plants vary widely in their water needs. Seedlings, for example, have limited root systems and may need daily watering, especially during hot, sunny weather. Established trees and shrubs, on the other hand, should have extensive root systems and may do just fine with what nature provides, needing supplemental watering only during extended dry spells. In reality, a plant's water needs depends on many factors, including the type of plant, its stage of growth, type of soil, weather, and time of year.
A berm of soil around these transplants ensures that water will soak into the root zone, rather than running off. Learn how to create a water-wise garden.
When you water a plant, apply enough to moisten the plant's entire root system, which may extend deeper and wider than you imagine. Then allow the soil to dry out slightly before watering again. Apply water slowly so it's absorbed by the soil rather than running off — a soaker hose or drip system is ideal. Avoid daily light sprinklings, which encourage roots to grow near the soil surface where they're vulnerable to drying out.
Rather than relying on a schedule, water plants when they need it. Poke a finger into a planter or use a trowel to carefully dig near a plant to check soil moisture.
The soil was plenty moist, but this hydrangea still wilted in the heat of the day.
Myth: Wilting is a sign that it's time to water
Wilting is a sign that the leaves aren't getting enough water, but that doesn't necessarily mean that the soil is dry. Anything that damages plant roots can prevent them from taking up water.
Roots need access to both air and water. Too little water and the roots die from lack of moisture. Too much water and roots can suffocate from lack of air. Both situations reduce the roots' ability to deliver enough water to stems and leaves, resulting in wilting. Root diseases, physical damage (such as from hoeing or shoveling), and soil-borne insects can also harm roots.
Damage to stems can also cause wilting. Some diseases and insects (especially borers) prevent water distribution throughout the plant, causing some or all of it to wilt. The only way to tell if lack of water is causing wilting is to check soil moisture.
Water droplets won't scorch leaves, even on the sunniest day.
Myth: Overhead watering on a sunny day can scorch leaves
It's wise to avoid using a sprinkler to water your garden on a sunny afternoon, because much of the water will be lost to evaporation. But the idea that water droplets act like tiny magnifying glasses and burn plant leaves has no basis in fact.
Leaf damage can be caused by all sorts of things, including:
too much or too little soil moisture
fertilizer burn from improperly diluted synthetic fertilizer
herbicides
insect or disease problems
weather conditions such as wind or frost
A strong stream of water can dislodge some pests, such as aphids, keeping them in check without resorting to pesticide sprays.
Myth: Overhead watering with a sprinkler is bad
Yes, it's usually best to apply water directly to the soil around plants rather than watering with a sprinkler. More water reaches roots. Less water is lost to evaporation. Foliage stays dry, minimizing disease problems.
But there are times when an overhead shower is called for. During dry, windy weather a thin layer of dust can build up on leaves, reducing the plants' ability to photosynthesize efficiently. Some insects, including aphids and spider mites, can be kept in check by simply hosing them off plants. Finally, heat-stressed plants that have wilted even though their roots are moist can get some relief from a cooling shower.
Even drought-tolerant perennials, like gaillardia, need regular watering their first season or two, until they get established.
Myth: Drought-tolerant plants don't need to be watered
Many young echinacea, sedum, and black-eyed Susan plants have perished because these "drought-tolerant" plants didn't get sufficient water at planting time and during their first season of growth.
When you set out a new container-grown plant, the roots are confined to the shape of the pot. The plants need a consistent supply of water during their first growing season, until their roots grow out into the surrounding soil. Water them as you would your annual flowers in their first season. During their second and subsequent growing seasons, drought-tolerant plants may need supplemental water only during extended dry spells.
Note, however, that just because a plant is drought-tolerant doesn't mean it doesn't fare better with a regular supply of moisture.
All articles are copyrighted and remain the property of the author.
By Dan Heims, President, Terra Nova Nurseries, Inc.
Photographs courtesy of Terra Nova Nurseries, Inc.
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