Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
3/5/01
Contacts:
Jeff Iles, Department of Horticulture, (515) 294-0029,
iles@iastate.edu
Elaine Edwards, Continuing Education and Communication
Services, (515) 294-5168, eedwards@iastate.edu
Yard and Garden Column for the Week Beginning March 9
The Plant Guy Returns!
By Jeff Iles
Extension horticulturist
Iowa State University Extension
Hey, Plant Guy:
The word's out. My yard has become an all-night diner for
every rabbit in the neighborhood. They seem to lay low
during the daylight hours, but at night, out they come with
their cafeteria trays ready for another trip to the tree and
shrub smorgasbord. I guess the fault can be placed squarely
on my shoulders. Because of my enthusiasm for new and
unusual plants, I've inadvertently created a feeding station
that would earn a 4-star rating from even the most finicky
rabbit. For example, the soft, supple foliage of my
arborvitae is perfect for my furry friends with a delicate
constitution. Oh, and don't forget some crabapple bark for
building strong bones, healthy teeth and gums. And for
rabbits entering their twilight years needing a little
roughage in their diet, how about a few viburnum tips? Go
ahead and laugh Plant Guy, but this feeding frenzy is
costing me big bucks! And don't tell me to get a couple of
dogs to drive these freeloaders away. I've already got two
mutts and neither is quick enough to catch up with these
uninvited dinner guests. What I really want to know is,
what kind of damage have the rabbits done and what is the
prognosis for my ravaged landscape?
Under Siege in State Center
Dear Under Siege:
I have good and bad news for you. First the bad news. If
evergreens like arborvitae, juniper, pine, etc., have been
stripped clean, there's probably little hope for survival
and you might as well remove their remains from the
landscape as soon as you can. But in the case of spirea,
viburnum, lilac or other deciduous woody shrubs, all is not
lost. These plants have the ability to regrow from
uninjured and surviving stubs, shoots and other growing
points located just below the feeding injury. In fact, you
might be surprised how well shrubs like spirea and
potentilla recover after being mowed off by marauding
rabbits. For shrubs like lilac and viburnum, simply prune
out the damaged shoots (just below the feeding injury) and
stand back. By mid-summer injured plants might look as good
as new. With trees like crabapple and serviceberry,
however, we'll have to take a "wait and see" approach. If
the tree has been completely girdled (bark eaten away around
the entire circumference of the tree), and if the tree is
not able to regenerate tissues needed for water and food
transport located just underneath the bark, then your tree
is history. But, if an injured tree is able to reestablish
these vital vascular connections, there's hope. In either
case, you might have to wait until late spring before you
pass judgement on a girdled tree. I've seen trees produce
leaves and look completely normal after suffering girdling
injury, only to die a few weeks later. Others have made
miraculous recoveries. At the very least, you now
understand the importance of protective fencing and how much
easier it is to prevent than fix rabbit damage.
Hey, Plant Guy:
Because my home faces north, my driveway, walkway and porch
have been covered with a sheet of ice since the middle of
December. Our mail carrier has adapted to this hazard by
routinely strapping on a pair of ice skates before venturing
onto our property. But knowing how to skate shouldn't be a
prerequisite to visiting our home, so I've tried my best to
get rid of the ice. I've had pretty good success melting
this mini-glacier with a mixture of sand and salt and was
feeling pretty good about avoiding a personal injury lawsuit
when my mail carrier suggested that all of my "salt
slinging" could harm my landscape plants. At first I
thought he was just being ornery since I'd deprived him of
his daily skate, but recently his words of warning were
echoed by one of those plant guys on the radio. So what
gives? Am I doing irreparable harm to my trees and shrubs
by salting down my front yard?
Getting a Grip in Grimes
Dear Grip:
Just so you know, there may be a lot of plant guys on the
radio, but there's only one Plant Guy! Now about your
de-icing salt question. Yes, sodium chloride (the principal
ice melting ingredient) can be very harmful to your
landscape plants because, (1) chloride ions absorbed by the
roots can accumulate to toxic levels inside the plant, (2)
sodium can limit the uptake of other important mineral
elements, (3) salt spray drifting onto plants can reduce
their cold hardiness and overall vigor and (4) salt-laden
soil will tenaciously hold onto water to the detriment of
landscape plants. But this unhealthy situation can be
remedied with a thorough "fresh water flush" after the
ground thaws this spring. Spring rains usually are
sufficient to wash sodium chloride through the soil profile
and away from plant roots, but if rainfall is scarce in
April and May, you might have to intervene, garden hose in
hand, and do the flushing yourself.
Hey, Plant Guy:
For the past 10 winters, I've smugly watched as my
neighbor's white pine turned sickly yellow and then
reddish-brown while my stately white fir shook off the
insults of winter and remained a handsome bluish-green.
I've always attributed the way these two conifers handled
winter to my superior horticultural knowledge. At least
that's what I've told my neighbor. But I fear my cover's
been blown. You see, this winter my previously flawless
white fir has developed branch upon branch of brown needles.
How can this be? I thought white fir was immune to winter
browning.
Eating Crow in Cresco
Dear Crow Eater:
As you now know, winter browning on white pine and the lack
of browning on white fir are more attributable to genetic
traits than to any cultural task you might have performed in
the past. The simple fact is, white pines in our region
almost always suffer some kind of winter injury with the end
result being brown needles. Winter winds have always
received the lion's share of the blame for winter browning,
but we now understand that it's the combination of
desiccating wind, winter sun and widely-fluctuating
temperatures that cause most of the browning on plants like
white pine, yew and hemlock, among others. And you're
right, traditionally white fir has been sparred the
embarrassment of a brown, late winter mantle. That is,
until this winter. Why the change? While we don't know for
sure, it is certainly within the realm of possibility that
dry conditions last summer and fall played a role. In
"normal years" (if there can be such a thing in Iowa), we
have ample late summer and fall precipitation that "ready"
our evergreens for the long winter ahead. But drier than
normal conditions in 2000, and even in 1999, might have
weakened and predisposed our evergreen plants, including
white fir, to the browning we see in the March landscape.
What to do? In a word, water. If conditions remain dry
this spring, it is critically important we lend a hand and
water at least once a week.
ml: isugarden
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