Drought – Watering Trees

Plants must have water to survive. Water in a plant is like blood in an animal. Water carries dissolved nutrients, sugars and hormones throughout the plant’s system. Some plants can go for long periods receiving only minimal water. Others require water every day. Here are some guidelines to help you determine when, where and how much to water.

During drought or watering restrictions, consider the replacement cost of the plants in the landscape and do what you can to save the most valuable plants.

Survival Watering

Overhead sprinklers are less effective and they promote pest problems by constantly wetting the foliage.

Hand Watering

During watering restrictions, selectively hand water trees. The direct application of water to the root zone of the tree, provided it is applied slowly enough to be absorbed by the soil, uses less water and is more efficient than sprinkler irrigation.

To avoid runoff when using the hand-held hose, use a water wand or other nozzle that divides the spray into rain-size droplets. Some nozzles have built-in spray pattern adjustments.

• Apply 2 gallons of water for every inch of trunk diameter (measured at 4.5 feet above the ground) for each day between individual waterings.

Example: a 10-inch diameter tree watered 3 days ago would need 60 gallons of water.

Note: a typical garden hose can deliver 5 gallons of water per minute. Sixty gallons would take 12 minutes to apply. Distribute this amount of water under the crown of the tree.

• Apply survival-level water every three days, when it hasn’t rained, to recharge the soil water.

• Don’t water daily, especially on heavy clay soils.

Soaker hose

A soaker hose, placed around a tree under the drip line, can apply a large amount of water effectively.

To determine how much water your soaker hose delivers:

• Coil it up and put it in a large plastic garbage bag.

• Cut a small hole in one corner of the bottom of the bag.

• Connect the soaker hose to your garden hose. Turn on the water.

• Suspend the soaker hose (in the bag) above a five gallon bucket. Allow water to drain into the bucket.

• Time how long it takes for the hose to apply five gallons of water.

• Use your math skills to determine how long to let the soaker hose run under the tree.

• Apply the amount of water determined above.

Locate your hoses at or close to the drip-line of the tree. The drip-line is an imaginary line that can be drawn out at the farthest extension of the branches. To conserve moisture between waterings, keep a 2″-4″ layer of mulch over the root system. Good mulching materials are pine straw, wheat straw, pine bark, wood chips, etc.

Timing your waterings is very important. Local watering bans may dictate your actions. The ideal time to apply moisture is between the hours of 10 pm and 8 am. Trees pick up more water during those hours, there is less evaporation and you can minimize the disease potential by not extending the normal wet period on leaves.

Young trees are particularly susceptible to competition from turfgrass. Remove all grass from the trunk out to a foot beyond the drip line.

One to two deep waterings are much better than many shallow or light waterings. Shallow watering encourages shallow roots which in turn makes the trees even more prone to drought stress.

If restrictions do not allow you to water outdoors at all, prune back small trees by one-fourth when they become severely wilted and begin shedding leaves. This will reduce water demand on the roots and increase their chances of survival during drought.