The advancing menace of global warming has brought significant changes in weather patterns around the world. A large portion of theUnited Statesis currently stricken by record breaking drought. It is commendable that local governments are devising water conservation plans. However, these plans unfortunately often start with restrictions or complete prohibitions on watering the landscape.
It is true that watering lawns and other things growing in your yard can be considered unnecessary in a time of crisis, but failing to water trees during drought is penny wise and pound (or dollar) foolish. Trees only require 62% of the water lawns need and actually conserve water while helping to make rain!
An estimated 62% of precipitation occurs over land and trees are a big part of it. “They pump ground water into the sky [through transpiration], the moisture then condenses and falls as rain,” explains Nick Nuttal, of the United Nations Environment Programme. Trees are one way of storing and returning moisture to the air so as to increase the chances of regular rainfall throughout the year. For example, a large oak tree can transpire 40,000 gallons per year.
When rain does come, trees decrease water pollution by slowing the rate at which it hits the ground. This reduces runoff of garden pesticides, bacteria from animal waste, and nasty stuff from streets reaching waterways. It prevents erosion of precious topsoil and lets helpful bacteria in the soil and the tree itself breakdown pollutants [phyto-remediation – how’s that for a word of the day!]. Trees conserve water by allowing more rain to soak in and recharge groundwater through the pathways made by the roots.
Ok, so now you are convinced. You cannot let your trees be fatalities in the war against drought, but what to do?
- Educate decision makers of the need to keep trees alive during drought.
- Be part of the process of creating sensible water conservation plans.
- “Harden off” your trees, with a gradual reduction of irrigation (fewer, deeper waterings). Sudden changes in watering patterns are most difficult for a tree.
- Water with a very slow drip from a hose so it all soaks in.
- Build earthen berms or basins around trees and pour in shower warm-up water caught in a bucket.
- Install drip watering pipes on young trees as we do at TM.
- If your local codes allow, install cisterns to store rainwater and household gray water for landscape use.
- Turf, flowers and shrubs cost you money and will come back once water is again available. Trees pay you in so many ways and will be lost forever without a regular source of water. If we are going to curb global warming we must preserve the existing urban forest.
Our Tree Service calls are increasingly to remove trees that have died of thirst. Most people seem to know that trees need water but not much more.
New trees need five gallons or so a week from you or rain for the first year. After that start giving more water less often with the goal of only having to water during dry seasons by year five.
Extended dry spells stress trees, especially those not “drought tolerant” by nature. Less growth, smaller or sparser foliage, and reduced pest resistance may result in decline and death.
Watering a tree like a lawn will result in surface rooting and drought vulnerability. Better is infrequent, deep soakings to a depth of one-two feet to encourage deeper root growth.
Allow the soil to dry out partially between watering. Keep in mind that roots extend far beyond the tree trunk and it is the roots you want to water – not the trunk. Sprinklers are better than nothing, but soaker hoses work best and a layer of mulch will conserve water.