Who doesn’t love new snow? The white blanket softens
the world and makes everything look new.
And it’s a good thing for the garden. Snow cover
insulates the soil so it is less likely to thaw and then freeze again.
Enveloping snow protects plant tissue from cold snaps and adds
moisture when it melts in spring.
It’s true that a heavy, wet snow can bend or occasionally
break tree branches (though most branches bowed by snow will
snap back if left alone). And deep snow can hide the burrows
of bark-chewing rodents. But most problems from snow actually
come from the things we do to remove it.
The worst of these is salt. Common rock salt — sodium
chloride — is cheap and ubiquitous, and many homeowners
reflexively scatter salt whenever they shovel or even instead of
shoveling. But salt can badly damage plants.
When salty water soaks into the soil, salt can accumulate
to toxic levels in plants’ roots. Salt also dries out leaf tissue on
contact, so the plant cells die of drought. If you see shrubs that
are brown in spring on the side toward the road or sidewalk, salt
is likely the culprit.
Salt spray from cars on busy roads can be thrown several feet.
Salt on sidewalks or driveways can be tossed onto plants by a
shovel or thrown far out into the yard by a snow blower. And
salt scattered on concrete and asphalt is eventually washed off
into the storm sewers to become a pollution problem.
The best way to protect your plants is by being thoughtful
about how you deal with snow. Before the first snowfall, make
a plan.
Vow to use salt only if absolutely necessary and never as
the first resort. Consider using a product based on calcium
magnesium acetate, which causes less damage to plants than
sodium chloride or calcium chloride, though it does not work
well in very cold temperatures. Whatever you use, use as little
as possible.
If you use a snow-removal service, talk with them about
using salt only when necessary for safety.
Some municipalities have tried spraying a less polluting deicer
derived from beet juice, which has a high freezing point
and dyes snow brown so it absorbs more sunlight and melts
faster. But the beet juice de-icer is expensive and is not yet
available in a form for use by homeowners.
Decide where you will deposit the snow you remove. If the
snow won’t contain salt or another ice-melting product, dump
it on a lawn or garden bed where it can soak into the soil, not
on a sidewalk or driveway where it will melt and then refreeze as
ice. If you use salt on your sidewalk or driveway, try to dump the
salt-contaminated snow where it will not run off onto the lawn
or plants when it melts.
Plan to shovel promptly. Shoveling twice is better than
waiting until all the snow has fallen because it reduces the
chance that the snow will get trampled down to a layer of ice
that will tempt you to spread salt.
Trim evergreen ground covers such as ivy back to the sidewalk’s
edge to make it easier to shovel and keep the plants from
being torn up by a snow thrower.
To protect special evergreens that might be damaged by a
heavy snowfall — such as arborvitaes with vertical branches
that collect and hold snow and are easily broken — consider
tying the branches loosely together with old panty hose or
another flexible material.
If you have a small or young tree near the sidewalk or
driveway, wrap wire cloth around its trunk to protect the
bark from shovels and snow blowers (and burrowing rodents).
Remove the protection in spring; if you leave it, the wire could
girdle the tree.
Some gardeners wrap vulnerable shrubs in burlap to protect
them against snow loads or salt. It’s hard to say which is less
attractive: salt damage or burlap five months out of the year.
The best alternative is to choose sturdy,
hardy shrubs and site them where they are
not at risk of damage.
Even if you don’t spread it yourself,
salt remains a reality in Chicago winters.
When a strip of parkway lawn along the
street is patchy and weed-ridden, think
of salt. Passing cars can throw salt-laden
spray several feet and grass is more vulnerable
than many weeds.
Some species have better tolerance
than others, but no plant likes being
sprayed with salt or having its roots in
salt-soaked soil. Drought, compacted soil
and other stresses will compound the
harm. And since visible damage may not
show up until summer, many gardeners
don’t connect it with salt.
Along busy streets and driveways, it
may be wiser to plant a fairly salt-resistant
ground cover such as English ivy or liriope
rather than grass. But don’t tuck bulbs
such as daffodils into the ground cover
because they are very sensitive to salt.
Among perennials, daylilies
(Hemerocallis) and Russian sage (Perovskia
atriplicifolia) are both quite salt-tolerant
(one reason the combination is so ubiquitous
in parking lot islands). Rugosa rose
(Rosa rugosa) and yarrow (Achillea) also
handle salt fairly well.
Perennial ornamental grasses such
as feather reed grass (Calamagrostis acutifloria),
switchgrass (Panicum virgatum)
and bluestem (Andropogon) are good
candidates for areas with salt spray if
you don’t cut them back in fall. Most
of the spray will cling to the dried top
growth, which you will remove, and
the salt with it, when you cut back the
grasses in early spring.
On the other hand, broadleaf evergreens
such as boxwood, which are not
completely dormant even in winter, are
certain to suffer from contact with salt.
That’s one reason we see so much winter
kill on boxwood hedges along sidewalks.
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Salt Resisters The Morton Arboretum lists relatively
salt-tolerant trees and shrubs on
its website. Remember, though, that
salt tolerance is not the only thing that
matters. Choose a plant that also has
the right sun and soil requirements for
your site. Deciduous Trees and Shrubs
-
Apple serviceberry (Amelanchier x grandiflora)
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Northern catalpa (Catalpa speciosa)
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Summersweet (Clethra alnifolia)
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Cotoneaster (Cotoneaster species)
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Smooth sumac (Rhus glabra)
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Bald cypress (Taxodium distichum)
Evergreen Trees and Shrubs
-
Chinese juniper (Juniperus chinensis)
-
Creeping juniper (Juniperus horizontalis)
-
Mugo pine (Pinus mugo)
-
Blue spruce (Picea pungens)
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