July 25th, 2012
Trees suffering amidst nationwide droughts
With more than half of the continental United States in some stage of drought, what can homeowners do to keep their trees healthy during hotter, drier summer months?
“While it’s impossible to keep every tree in good health in times of severe drought, taking a proactive approach for a prized or sentimental tree can support its good health,” recommends Tchukki Andersen, staff arborist with the Tree Care Industry Association. “A plan that is supported with good cultural practices, proactive monitoring for pests and disease, and response to warning signs is more likely to survive.”
A tree’s first damage from drought occurs beneath the soil line in the form of root damage, long before any outward signs of trouble. That’s when “opportunistic” pests make their move. Boring insects are thought to be drawn by the chemical and acoustic signals of stressed trees. The sound of water columns breaking cues the borer to invade the tree and lay eggs. Andersen recommends applying a 3-inch layer of organic mulch or wood chips over the root zone at least out to the drip line.
While all trees are at risk during long period of drought, some are more prone to its effects. New transplants are highly vulnerable to drought stress, and supplemental watering for the first few years of establishment is necessary, to the extent that it’s allowed. But even mature trees are suffering.
Watering trees deeply with soaker hoses or irrigation systems - as opposed to brief, surface watering - helps sustain trees. But it’s very difficult to do much for a large tree because of the massive amounts of water it needs. With so many trees affected, Andersen recommends watering only those trees that you can help.
Drought exacerbates matters for trees already under stress, like those on dry slopes, surrounded by pavement, or improperly planted. In landscape situations, consider taking action, such as moving smaller trees to a better location, alleviating compaction, or replacing moisture-draining lawn with a layer of mulch. A two- to three-inch layer of compost will help trees in maintaining moisture.