The Homeowners Column

The Homeowners Column

Not Too Late to Help Trees and Shrubs

Photo of Sandra Mason

Sandra Mason
State Master Gardener Coordinator
slmason@illinois.edu

Unfortunately we know the scenario all too well. Green fades to brown. Lawns are the first to give up and go dormant during drought. Relatively healthy, established lawns should survive at least 6 weeks without any rainfall or irrigation. Grass blades won't be green, but the crowns and roots will be alive to regenerate the lawn once favorable temperatures and moisture return. Lawns that have not had any measurable water in six weeks will benefit from a sparse irrigation of approximately one quarter inch of water every 2 weeks to keep grass crowns and roots alive.

Lawns are the fabric that binds our landscape together. We notice their dramatic dormancy first but often miss drought symptoms of our trees and shrubs. Lawn may be an integral part of our landscape; however, their replacement is relatively easy compared to replacing a mature tree.

Trees show drought stress in a variety of ways. Leaves may wilt, droop, curl, turn yellow, and turn brown at the tips, between veins or along margins. Green leaves, stems, roots and fruits may shrivel. Shrinking can cause radial cracks in young tree trunks. Leaves of ash, linden, hickory and black locust may turn yellow and drop early. Many plants including burning bush, river birch, flowering dogwood, and red maple may show early fall color. Pine needles may bend or droop near the needle base. Needles then either fade and turn brown or remain green and permanently bent.

Trees and shrubs vary in their drought tolerance. Shrubs such as potentilla, hydrangea, viburnum, burning bush and holly are particularly susceptible to drought stress. Bald cypress, beech, flowering dogwood, magnolia, Japanese maple, spruce and douglasfir are often the first to suffer. Native trees which tolerate drought include Kentucky coffeetree, hackberry, hickory, hawthorn, black oak, bur oak and shingle oak.

It's not too late to help your trees and shrubs even if they show symptoms of drought stress. For plants in the ground for more than three years the goal is to provide at least 1 to 2 inches of water every two weeks. It takes about one inch of water (about one half-gallon of water per square foot) to wet the top 6-15 inches of soil where most tree and shrub roots live.

Tree roots may extend two to four times beyond the tree's crown so watering exceptionally large trees can be difficult and time consuming. Just keep in mind how much you would miss that mountain of a tree. In general applying enough water to penetrate deeply within the dripline (the area between the trunk and the ends of branches) will benefit most trees.

A root needle, also known as a root feeder, attached to your garden hose is one suitable watering tool. Their use can, however, be time consuming since they have to be moved frequently. Be sure to use low water pressure so as not to produce underground air pockets.

Soaker hoses are an efficient option, but are best for small trees and shrubs. Water does not move laterally from the hose so soakers may also have to be moved several times to get good coverage. Tree bags or buckets with small holes are also useful for small trees to provide slow thorough watering.

For large trees, sprinklers are the best watering method. Water early in the morning to reduce water loss through evaporation. Sprinklers may need to run 90 to 120 minutes. To figure timing place a 1-inch tall can such as a cat food can, near the drip line. As soon as the can is filled, empty it and allow it to refill once more.

Avoid heavy pruning or fertilizing at this time. Check with your municipality for any watering restrictions during drought then do your best rain dance.

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