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Care of
Weather
Injured
Trees and Shrubs |
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After a year of hail storms,
early fall snowstorms, and late spring hard freezes,
there are a lot of seriously injured landscape
plants around Wyobraska. The combination of
adverse weather events that have struck the region
over the past 12 months may be the worst I have seen
in 30 years, and the injuries to the region’s
landscape trees and shrubs resulting from that year
of adverse weather, may likewise be the worst I have
seen in that time. Some bad weather years in the
1990’s killed or seriously injured many of the
region’s American and Siberian elms, but those trees
were already in trouble before the weather finished
them off. The injured plants that I am seeing in
the region’s landscapes this summer tend to be young
and otherwise fairly healthy trees and shrubs.
The October snowstorms tore still green leaves from
not yet dormant branches and likely froze the still
not dormant branches and stems of plants like
butterfly bush, blue mist spirea, and some of the
shrub roses.
Winter (actually fall) death
loss of butterfly bush and blue mist spirea were the
highest in over 10 years. Most of the hardy shrub
roses will survive, but died back to near ground
level. Most of the shrub roses have vigorous new
growth returning from near the base of the plant,
and only require the dead stems to be pruned off,
but many butterfly bush and blue mist spirea do not
appear to be leafing out at all this spring and
should be replaced. In Wyobraska these popular
shrubs should really be sold as “perennial” shrubs,
meaning that they need to be cut back each spring to
the point on the main stems where growth returns in
the spring. Like most perennials, these
summer-flowering shrubs tend to reach full size in
one growing season, so a major haircut each spring
does not really set them back. Expecting to
replace these shrubs every five years or so is a
good idea, because usually within that time frame
some severe winter or early hard freeze in the fall
will kill or so severely injure these plants that
replacement is the best course of action. I think
that their summertime flowering in our Wyobraska
landscapes is well worth the occasional replacement
cost and effort.
The early October snowstorms
also appear to have caused some major damage to
trees, with dead branches showing up in much higher
than normal numbers this spring. In some cases, it
will be possible to simply prune off the dead
branches. In other cases the extent of branch death
is such that removal of the entire tree is probably
the best approach. Even some trees that are fully
leafed out appear to have suffered some injury from
last fall’s pre-dormancy blizzards. The effect
shows up as stunted and yellowish leaves on entire
branches. I suggest not pruning these branches
until the extent of their injury is better known.
The best care for any injured
plant is to give it everything that it needs to grow
in a healthy manner. That means water, fertilizer,
and mulch. Recovering from hail and freeze damage
can use up much a a tree’s stored energy reserves,
and the best thing the owner of the tree can do is
to help the tree capture and store as much energy
this year and for the next few years as possible.
Trees use their energy reserves to flood injured
sites (like where a hailstone hits and cracks open
the bark) with chemicals that repel insects and with
the sugars and starches necessary to regrow new bark
over the opened branch. That can take a lot of
energy. Water, fertilizer, and the very helpful
rooting environment that mulch creates can make a
make difference in a tree’s capacity to capture the
sun’s energy and use it to build the sugars and
carbohydrates from which the tree makes its new
bark, the buds for next season’s leaves, and even
the tannins and other toxic substances that trees
put into the injured sites to repel insects and
other predatory organisms like bacteria and fungi.
I’m not a big fan of spraying injured trees for the
simple reason that it does nothing to help the tree
to help itself. While it may kill of few of those
initial predatory insects and organisms, the spray
does nothing to help the tree in the long run.
Relatively new studies on how
best to fertilize trees suggest that fertilizing
close to the trunk may be better than the former
recommendation of fertilizing out by the dripline—the
edge of the tree’s foliage. Fertilize before the
end of July. An 8 foot diameter mulch circle
around injured trees is recommended. Mulch should
be 3-4 inches thick.
Fertilizer, mulch, and water
are also the best treatment for injured woody
shrubs—along with pruning off any severely injured
branches.
Finally, try to avoid any
further injuries to your trees with the coming
weekend of fireworks. Enjoy the 4th! |