August 22, 2001
Stillwater Gazette
Betsy Halden

How much water does our garden need?

Our Valley received loads of rain this spring. During July and August the weather has been dry. Most of us have been watering everything frequently. Plants in containers and pots need extra attention. The following suggestion may help you with deciding how much water to give your garden.

How often do we need to water? Adeep watering once a week should be adequate for fruit, vegetable, and flower gardens. This means applying 1 to 1 ½ inches of water per week. This amount is also adequate for an established lawn. Roses such as hybrid teas, floribundas, and grandifloras, need a thorough soaking every 7 to 10 days. The key to watering newly planted trees and shrubs is to check the moisture 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). The root-ball or root-mass can dry out quickly and its 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. Water less frequently and enlarge the watering area as the plant’s root system begins to grow into the back-filled and surrounding soil. Small trees usually require watering for 1 to 2 growing seasons. It may be necessary to water larger trees for 3 to 4 years.

These are general guidelines for watering. The actual frequency and amount of watering is mostly determined by soil characteristics and weather conditions. Sandy soils require more frequent watering than loam soils. We should adjust our watering practices to specific weather and soil conditions.

When should we water? When using 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. Watering in the morning also give time for the plant foliage to dry. Watering at midday is less efficient. Evaporation is rapid and strong winds may cause uneven water distribution. Strong midday winds may also carry water onto driveways, patios, and streets. This results in 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 irrigations systems and soaker hose are more efficient and cause fewer disease problems than sprinklers. Mornings and evenings are excellent times to water gardens with 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 limits weed competition. Organic materials such as grass clippings, straw, shredded leaves are excellent mulches for vegetable gardens. 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 the types of plantings. Apply wood chips and shredded bark to a depth of 3 to 4 inches around trees and shrubs. The best depth for mulches in the vegetable garden ranges from 2 to 3 inches for fine materials such as grass clippings, to 6 to 8 inches for straw.

Are you interested in becoming a University of Minnesota Extension Service Master Gardener? Call the Washington County Extension Service office, 651.430.6800 for an application.

Betsy Halden is a Master Gardener with the University of Minnesota Extension Service. University of Minnesota Extension Service materials were consulted in the preparation of this column. You can reach Betsy Halden at eahalden@comcast.net