Tree Watering

How

The best ways to water trees are by soaker hose or trickle (drip) irrigation. Irrigation should ideally be done when the soil moisture reaches a critical measured level (use a tensiometer or gypsum blocks). Sprinklers are less efficient. Even a garden hose, moved often, can provide a good soaking. Do not water only at the base of the trunk, except in the case of small, newly planted trees. This can lead to pest problems.

Deep watering a tree with a pipe stuck deeply into the soil (i.e. 16-24 inches) is not as good for trees as surface applications. Most of the absorbing roots are in the top foot of soil. Deep watering below this level misses the active roots and allows water to drain away, although some apillary water will rise upward into the root zone.

Where

Set water hoses or applicators around the outside edge of three crown just beneath the foliage. Be sure the water soaks in well. Use slow application rates on slopes where runoff may waste water. Trees will take up a good share of the water even if surrounded by grass.

You should never spray the foliage of trees when watering. Water droplets on trees can lead to pest problems and destruction of leaf tissue through sun damage.

When

The best time to water is at night from 10 p.m. to 8 a.m. Watering at night allows less evaporative loss of water, so more water moves into the tree. Any water shortage in the tree will usually be removed overnight. These application hours also minimize pest problems on ground covers and turf.

Trees use water night and day, season to season, whether leaves are present or not. Trees use water all year. Dormant season water during winter droughts can help your trees.

How Much

Depending upon soil texture, daily temperatures, and rainfall amounts, 1-3" of water per week should keep a tree growing. Five gallons per square yard (550 gallons per 1,000 square feet of root zone) is about 1 inch of water. Fine soils require careful attention to prevent over-watering and root death.

How Often

Trees should be watered once or twice a week in the growing season if there is no rainfall. A few heavy waterings are much better than many light, shallow waterings. A greater proportion of the applied water is utilized by the trees with heavy watering. Also, light watering encourages shallow roots that can lead to more severe drought damage. Once you begin watering you should continued to water until the rains come.

Other Things

Many plants in a small area can be competing within the soil to pull out enough water for themselves. This water competition can be severe. Remove excess plant competition from around any tree to decrease water stress. Use mulch to conserve water and to prevent weed competition. Careful application of herbicides can also reduce weed competition for water.

When landscape watering is not allowed because of water-use restrictions, "gray water" may used, if legal. Gray water is waste water from the bath tub, shower, sink, dishwasher, or washing machines. You may check to see if it is legal in your county or city. Gray water will plan a greater role in water conservation in the future.

Xeriscaping, or developing water-efficient landscape, is becoming more important.