Submitted by Ruth Chatterton on behalf of the Bedford Arbor Resources Committee
Trees around town are having a tough summer due to the drought. Drought stress might not cause the instantaneous death of a tree, but it weakens its overall health, paving the way for secondary insects or disease infestations.
Why use scarce water on trees during a drought?
- Trees reduce the hot, dry conditions around reflective pavement. Trees that shade your house can make a big difference in your air conditioning bill.
- Trees are crucial to maintaining sufficient local water supply in our communities. When it does rain, a mature tree can capture thousands of gallons of rainwater in its canopy and root zone, sinking that rain into the soil and then into the aquifer.
- Dead or weakened trees can become a hazard to property, pets and people.
- Trees should be given a higher priority than lawns. A lawn can be replaced in a matter of months. A 20 year old tree takes 20 years to replace and you lose many of the benefits it offers during that time.
How much and how often should trees be watered?
- Trees need different watering than grass. The best solution is to use a soaker hose for many hours to ensure that water reaches deeply into the roots. Since every soil’s composition and drainage can be different (even on the same property), it’s best to check the soil 12” below grade after watering to make sure you watered deep enough. Watering for short periods of time encourages shallow rooting which can lead to more drought damage.
- The trunk doesn’t need water. Water about nine inches from the trunk out to the edge of the farthest branches (the drip line) – and even a little more. This is where the majority of the feeder roots are, but realize that trees on ledge or in heavy clay may extend roots 5 times the canopy.
- Water around the whole tree. Water should be distributed evenly under the dripline of the tree. Don’t waste water on the leaves since they do not absorb water.
- Twice a week is plenty for mature trees. Trees planted within the past few years or trees under stress need water more often. Other stresses include a location close to streets or buildings where roots are constricted, or where recent construction disrupted roots or foot traffic compacts the roots.
What else can we do to ensure trees survive?
- Mulch.Put a four inch layer of organic mulch around the base of the tree to slow water evaporation, keep the weeds down, keep the surface receptive to water, cool the root zone, and create a healthier environment for the beneficial microorganisms in the soil. Removing the turf around the base of the tree and replacing it with mulch can help eliminate competition for water between the turf and the tree. Remember to pull mulch back 6 inches from the trunk of a tree to prevent rot.
- Skip fertilizer and especially herbicidesuntil the drought ends. Tree roots are especially susceptible to root burn from the salts in fertilizers when there is not enough water.
- Prune. Remove any broken, dead, or disease-infested branches as they can cause additional weakening to a tree’s overall health. A tree with properly pruned branches will have improved structure and stability, helping the tree to withstand drier times.
Editor’s note: The Bedford Arbor Resource Committee, a town committee that advocates for trees. To learn more, visit www.bedfordma.gov/arbor-resource-committee You’ll find information about BARC along with a resource list of relevant links.