Most areas in Iowa received adequate moisture this spring. However, in recent weeks the weather has been quite dry. The following questions and answers on watering may help the gardener deal with watering related concerns.
How often do I need to water?
A deep watering once a week should be adequate for fruit, vegetable, and flower gardens. Apply 1 to 1 1/2 inches of water per week. A weekly application of 1 to 1 1/2 inches of water is also adequate for an established lawn. (Additional information on watering lawns can be found in the May 25, 2001 issue of the Horticulture and Home Pest News.) For modern roses, such as hybrid teas, floribundas, and grandifloras, a thorough soaking every 7 to 10 days should be adequate. The key to watering newly planted trees and shrubs is to check the moisture status of the plant's root-ball or root-mass. The roots of newly planted trees and shrubs are initially confined to the plant's root-ball (balled and burlapped plants) or root-mass (container-grown plants). Since the root-ball or root-mass can dry out very quickly, their moisture status should be checked frequently. Newly planted trees and shrubs should be watered when the root-ball or root-mass (not the surrounding soil) begins to dry out. To water the root-ball or root-mass, slowly apply water to the base of the plant. The frequency of watering can be reduced and the watering area enlarged as the plant's root system begins to grow into the backfilled and surrounding soil. Small trees usually require watering for 1 to 2 growing seasons. It may be necessary to water large trees for 3 to 4 years.
The above are general watering recommendations. The frequency and amount of watering is largely determined by soil characteristics and weather conditions. For example, sandy soils require more frequent watering than loam soils. Adjust your watering practices to specific weather and soil conditions.
When should I water?
When irrigating with a sprinkler, early morning (5 to 9 am) is the best time to water. A morning application allows the water to soak deeply into the soil with little water lost to evaporation. When watering is completed, the plant foliage dries quickly. Watering at midday is less efficient because evaporation is rapid and strong winds may cause uneven water distribution. Strong midday winds may also carry water onto driveways, patios, or streets, wasting considerable amounts of water. Watering lawns and gardens with a sprinkler in the evening or at night may increase disease problems.
In fruit, vegetable, and flower gardens, drip irrigation systems and soaker hoses are generally more efficient and cause fewer disease problems than sprinklers. Mornings and evenings are excellent times to water gardens when using a drip irrigation system or soaker hose.
Are there ways to reduce water use in the garden?
Apply a mulch around landscape plantings and garden areas to conserve soil moisture. Mulching reduces the rate of evaporation from the soil surface and also limits weed competition. Organic materials, such as grass clippings, straw, and shredded leaves, are excellent mulches for the vegetable garden. Wood chips, shredded bark, and ground corncobs are good choices for trees, shrubs, and perennials.
The depth of the mulch depends on the type of material used and crop. Apply wood chips and shredded bark to a depth of 3 to 4 inches around trees and shrubs. Optimum depth in the vegetable garden ranges from 2 to 3 inches for fine materials, such as grass clippings, to 6 to 8 inches for straw.
This article originally appeared in the July 20, 2001 issue, p. 93.