By Pat Curran, Horticulture Educator,
Tompkins County Cornell Cooperative Extension
Question: I'm confused about when and how much to water. Are there any guidelines?
Answer: Watering is a complex issue, but with the recent heat and drought, it's definitely on gardeners' minds. How much and how often to water depends on the plant, the soil type, and the temperature, but in general, when you do water, water deeply, to encourage deeper rooting and more self-sufficient plants. Avoid watering lightly and often, which allows plants to survive with shallower roots. Then vacation comes, and the plants suffer or die without their frequent "sprinkling."
The lawn should be LAST on your list. In 26 years, my lawn has never been watered. In our area, our cool season lawn grasses may go dormant (turn brown) in dry spells, but they seldom die from drought alone. We have several different species of lawn grasses, some more adapted to drought or shade than others. Mowing high is key, 3 inches if possible. Grass with more leaf surface has deeper roots, more drought resistance, and fewer weeds.
As a tree lover, however, I'd like to encourage more attention to tree watering. Newly planted trees and shrubs should receive a drink of 10-15 gallons of water each week, unless there is an inch of rain. Rain gauges are very useful, and it can be fun to keep track of how much rain your garden is getting. If it's very hot, in the high eighties or nineties, the new woodies may need watering twice a week. Sandy soil dries out faster than clay soil, so keep that in mind, too.
What about mulch? Mulch helps slow down evaporation from the soil surface. Mulch also decreases soil compaction from foot traffic or heavy rains. Organic mulches rot down to improve the soil and its water-holding capacity. But in a severe drought, organic mulches such as woodchips or bark can dry out and take up all the water that is being applied, before the water reaches the soil. The solution is to poke the hose end under the mulch and let the water run gently for a while. Avoid using sprinklers, which waste up to half of the water due to evaporation. Soaker hoses can be very useful. Wind them around plants, or down rows. Covered with mulch to protect them from the sun, soaker hoses can be left in place year round.
What about veggies and perennials? Veggie seed beds will need to be kept moist until the seeds germinate. Potted veggie transplants and container perennials will need watering every few days if it stays hot and dry. The goal is to keep the soil moist around their rootballs so the roots grow into the adjacent soil as quickly as possible. Sometimes, covering the new plants for a day or two is a good idea - it protects them from the blast furnace effect of the sun. Possible covers can include commercial row cover, a cardboard box, or an upended white plastic pot.
Last updated October 27, 2014