Big Trees Need Water Too

by Margaret Canavan,
GITC Board Member, Galveston Co. Master Gardener

Courtesy: Galveston Daily News

Islanders--and  “voting” friends everywhere--rejoice at the Galveston Island Tree Conservancy's $50K award from Tom’s of Maine for the 2012 Neighborwoods Project.  This is a big boost to Conservancy efforts toward the goal of 25,000 new trees for Galveston in five years, to replace some of the almost-40,000 trees lost to Ike.

These new trees need help to thrive. As important as planting is watering. Neighborwoods recipients pledge to water trees regularly for two years while they become established, as do recipients in Conservancy Tree Giveaways. The extended drought has inspired residents to develop creative watering techniques while observing restrictions. Saving “gray” water from bathing and washing, installing rainwater collection systems, and saving air conditioner condensate are a few good solutions.

But there’s more to be done: Big trees need water too. They are not immune to drought. News of millions of trees dying due to the region’s rainfall shortage illustrates this. The vast majority of a tree's roots are within just twelve inches of the soil surface, which becomes dry and hot during drought. These are the roots that provide most water and nutrients for the tree. Larger and deeper roots primarily provide anchoring for the tree but take in little water.

It is distressing to see that not all local residents realize the need to water established trees.  These trees have been growing for years, even decades, and many large trees are declining due to inadequate moisture.

Without significant winter rains, established trees will continue to need supplemental water during colder winter months as well. Moist soil also serves the purpose of protecting tree roots from freeze damage. Drought-stressed and root-damaged trees are more vulnerable to insects and disease than robust trees. Trees stressed or injured now will show more damage next spring.

The best way to irrigate a large tree is a slow soak under the entire canopy. This is easily provided by an inexpensive soaker hose or dripping water hose moved around the root zone. This minimizes evaporation and prevents sending water where it is not needed, such as sidewalks and streets. Mature trees have few roots near the trunk; most extend well past the dripline, and given space can grow more than twice the diameter of the canopy. One inch of water per week is ideal. Soil that feels dry to the fingertips needs water.

Tree canopies provide numerous benefits. They shade and cool the ground, reducing energy usage and maintaining soil moisture. An urban forest acts as an air filter, absorbing carbon dioxide and emitting oxygen. Tree root systems help maintain soil stability, reduce erosion, and help control water runoff. Big trees provide habitat for birds and other wild creatures. Trees are beautiful and a joy to see. A newly-planted small tree will take years to make a significant impact visually and ecologically.

Observe local watering restrictions, but water mature trees as you are able. Not just in Galveston, and not just the new ones that were purchased, received in a give-away, or acquired as a Neighborwoods tree.  Big trees need water too. Too many have been lost already. Let us all take care of our tree inheritance.

———

“Tree Stories” is an ongoing series of articles about island trees, tree care and tree issues. If you have or know of a special tree on Galveston Island that should be highlighted, email treesforgalveston@gmail.com. Margaret Canavan is a Galveston resident, a Galveston County Master Gardener, and a member of the Galveston Island Tree Conservancy Board.