NEW ULM - A Minnesota Department of Natural Resources (DNR) Fire Supervisor says the prolonged drought creates a hazardous situation for trees.
"With no moisture in the soil, alternate freezing and thawing can cause severe root damage in trees, even to the point of killing them," said DNR Fire Supervisor South Tom Romaine of New Ulm. "Mulching and watering trees take time. But this year it could make the difference between losing a saving a tree."
He said residential trees are particularly vulnerable, since yards don't have the natural mulch of forests, and heat reflected from buildings, walls and fences intensify the effects of drought.
Romaine said trees should be watered regularly this time of year as long as the air temperature is above 40 degrees and there is no snow cover. He suggested mid-day watering so it soaks in before possible night freezing.
His other points were:
Young trees especially need watering during droughts to prepare the roots for winter. Newly-planted trees should be watered at the base. More mature trees should be watered within the drip line of the branches.
Trees use water most effectively when it is allowed to soak into the soil slowly. Sprinklers, soaker hoses or soft spray wands work well.
Apply at least 10 gallons of water for each diameter inch of the tree. A tree 4 inches in diameter would need 40 gallons per watering.
Give each tree the equivalent of a 1-inch rain per week. Place a rain gauge under a sprinkler to help monitor tree watering.
Apply well-compacted much around the base of each tree to help conserve root moisture, prevent deep freezing, and prevent alternate freezing and thawing of soil. Popular mulches are straw, bark chips, composted leaf litter (leaf mold), or well-rotted manure.
If mulch is too loose, it may provide habitat for mice and other small rodents that can damage trees.
Mulch should be placed 3 to 4 inches deep and extend to the edge of the drip line of the branches on smaller trees. On large trees, mulch should cover an area at least four to five feet in diameter around the trunk. The larger the mulch area, the more the tree benefits.
"Be sure not to pile mulch against the truck of the tree or excessive moisture will build up, inviting decay and disease," Romaine said. "Pull mulch a few inches away from the base of the trunk."
Mulches are left in place over winter and either removed or worked into the soil in the spring. Bark chips can be left year around.