How to save your trees during the drought
Efforts to save water during the Southern Oregon drought could put trees at risk ― especially since most people don’t know the right way to water trees when they do turn on the spigot.
Most established trees are getting their water far from their trunks. Feeder roots that carry water and nutrients to the rest of the tree spread out far beyond the tree canopy, said Mike Oxendine of Plant Oregon, a nursery outside Talent.
“The thing that we need to do to protect our trees the most is to continue watering with a deep watering once a week,” he said. “Unfortunately, when we start to cut back our water, sometimes we cut back the water on the lawn and forget that our trees have been getting their water from that lawn for as long as they've been alive as well.”
The best place to water trees is at their drip line, Oxendine said.
The drip line is the perimeter around a tree that lies at the outer edge of the canopy.
Oxendine said to visualize the drip line, imagine a wine glass sitting on a dinner plate. The bowl that holds the wine is like the tree canopy, while the outer edge of the wine glass’s flared base is like the drip line. The plate that extends out from the glass’s bottom represents the feeder root zone.
Rather than using a sprinkler, Plant Oregon recommends using drip irrigation tubing to release drips of water around the tree drip line.
Drip irrigation tubing, also called pre-emitted tubing, is available at hardware and garden supply stores.
Oxendine said the amount of water a drip line emits varies, but a typical volume is four liters per hour.
That’s equivalent to about one gallon of water per hour.
In comparison, a standard garden hose delivers about 10-20 gallons of water per minute.
"It's a pretty slow, consistent drip, so you're not using a tremendous amount of water at all,“ Oxendine said.
Plant Oregon is recommending that people water their trees for up to three hours once per week using a slow drip system.
Spreading mulch around a tree will help hold in moisture and control weeds, Oxendine said.
Young saplings can show drought stress quickly, but older, established trees often suffer with few red flags ― at least in the beginning.
“The larger the tree, the slower the change is going to be,” Oxendine said.
In the first year with too little water, a tree may wilt back, lose some of its leaves and start to turn brown. As drought stress continues into the second and third year, beetles start infesting the tree ― triggering secondary infections of mold, fungus and bacteria, Oxendine said.
That combination can prove fatal to trees, he said.
“Usually it’s the one-two punch that knocks trees out,” Oxendine said.