Caring for trees stressed by
hot, dry conditions
By: Sandy Feather
I have noticed that many of the trees in my yard are
dropping leaves, some still green and others yellow. I have a sweet
gum, a linden and several black cherries. I imagine the very hot,
dry weather is to blame but want to be sure it is not some kind of
A. You are absolutely right that the weather is to blame. What
you are seeing is an environmental problem rather than a disease
problem. Diseases are usually species specific. It is unlikely that
the same disease would attack these unrelated trees. This has been a
rough growing season for woody ornamental plants.
The warm spell
in March forced many trees and shrubs to put out new growth much
earlier than normal, followed by frosts and freezes that damaged or
killed the tender new growth. As if that wasn't enough stress,
June was very dry and July started off with record high temperatures.
Frost is very destructive to frost-sensitive Japanese Maples
Early spring growing season
The early growing season also promoted a lot of quick
succulent growth. When those plants were hit by the hot, dry
weather, that growth lost moisture faster than more moderate growth
would have. The stress trees are under shows up as
yellowing and falling leaves
and premature fall coloration.
There are a few things you can do to help them.
Provide an inch of water a week if there is no rain. Soaker hoses
and drip irrigation are the most efficient ways to water. If that is
not an option, remove the nozzle from your hose and allow it to
trickle slowly around the base of the plant. Move the hose every
hour or so until you have watered the entire circumference of the
plant. Place the hose within 18-24 inches of the base of the tree.
A two- to three-inch layer of mulch
around the base of the tree, out to the drip line (ends of branches)
if possible, helps conserve soil moisture and moderate soil
temperature. It also helps keep weeds in check that would otherwise
compete with your trees for water and nutrients. A circle of mulch
around the base of trees and shrubs also keeps lawn mowers and
string trimmers away from their trunks. Many woody plants
(especially young ones) are killed outright by lawn mowers and
string trimmers damaging the bark.
Mulch will help conserve soil moisture
and moderate soil temperature
Avoid mounding excessive mulch up around the trunk of
the tree. Doing so can cause the bark to rot, and it creates a
perfect environment for insect and animal damage to occur out of
Keep mulch a few inches away from the trunk.
Excessive mulch is difficult to re-wet once it dries out completely,
so even when it rains, trees with mulch "volcanoes" are not
benefiting from it as much as they should.
Avoid pruning and
avoid pruning or fertilization now because this will push new growth
that only will add to the stress. It also may not harden off before
winter arrives. Do not fertilize without taking a soil test first.
Trees growing in a lawn situation receive more than enough when you
fertilize your lawn. They should not require additional
fertilization unless a soil test reveals a deficiency. If you do not
fertilize your lawn, or if the trees are growing in a bed, they may
benefit from a late fall application of fertilizer. The roots of
woody ornamentals put on a lot of growth late in the season.
best time to fertilize is when they have lost their leaves and gone
dormant, but the soil is still warm enough for root development.
This is usually late fall, right around Thanksgiving.
Fertilize trees in the northeastern US
around Thanksgiving -- After they drop their leaves
Common names of plants