AUGUST 25, 1997
by Mary Robson
Water! After a work day getting hot and sweaty, no matter what the work, taking a cool shower and tossing clothes in the washer is bliss. Even more than comfort, water means survival, and all of us expect clean water from country and city systems. Now that we've reached the dry end of summer, how can we best deliver water to thirsty plants?
Making one rule about watering for all gardens isn't possible. Watering needs for a garden depend on exposure (how much sun and light the area gets), soil type (sandy soils dry out faster than loamy or clay soils), and what sorts of plants are part of the area. The age of the plants makes a difference too, because older, established plants can handle dry spells more readily than new transplants.
A general rule is to apply water slowly, and to apply it at the root zone of plants. What type of water system is available obviously depends on the individual garden. The least efficient method is overhead sprinkling, which wets leaves but may not saturate the ground at the roots. Watering means roots, not leaves.
Soaker hoses (those delivered from recycled rubber) work by dribbling out small amount of gradually and wetting the root areas thoroughly. Drip irrigation systems also place the water at the plant roots. Developing a system that is reliable and easy to use us one of the challenges of gardening. If the system has automatic timers, return to manual during rainy spells to avoid wasting water.
When to water? If possible, choose early morning hours, starting about an hour before dawn up to about 10 a.m. Early evening hours also work well. Water applied at this time isn't lost to evaporation as readily as it will be during the hottest hours of the day from 10 a.m.. to 5 P.M. The worst way to water is with sprinklers at high noon, when nearly half the water disappears in evaporation.
The reasoning involved in watering in early morning is that plants can dry out during the day, which can help prevent potential disease problems such as black spots on roses. The wet spring of 1997 demonstrated how many diseases invade leaves that are constantly damp. If the irrigation system is set up so that leaves aren't being sprayed, this is ideal. Soaker hose systems of other ground-level delivery methods can run slowly at night once a week to soak root zones without wetting foliage or wasting water. If there is no concern about plant disease, watering at night or in the early evening is the most effective. Avoid watering during mid-day. Hand watering is generally effective only for containers and very small garden areas.
How can the gardener tell is water's needed? Look at the plants. Learn which ones are high water users, such as Rhododendrons, and group them with a soaker hose or irrigation system. Plant groups of low water-use plants to reduce the need to water the entire garden. Observe the leaves. If shrub shows droopy leaves, and the leaves feel fragile and floppy when touched, rather than firm, water's needed. Probe the soil under plants. Soil can be a bit moist on top and dry at the roots. If it's dry two to six inches down, give the plant a deep soaking, but no more than once a week.
The lawn needs water if it doesn't spring back when stepped on, and has a gray-green color. It's also possible to allow the lawn to go dormant in August. The grass will appear brown, but will revive with fall rains.
Many plants won't need water more than once a month in the summer, depending on weather conditions. Large established trees and shrubs usually manage without additional water. Be sure to watch, check, and water vegetable gardens, plants in containers, and plants in their first year or two in the garden. Roots aren't as efficient at dealing with reduced water supplies when they are newly planted.
Garden watering requires observation and thought. Gradually discover, by experience, how much the different areas of the garden need. Water management, like soil management, is a central skill to garden health. And while watering, consider the precious and limited resource that keeps our blue planet thriving.