I'm an award-winning garden writer, speaker and consultant in Chicago, where I was on staff at the Chicago Tribune for more than 20 years. Raised on the South Side by an organic gardener and environmentalist, I now garden in a leafy suburb on the edge of Chicago--in the deep shade on the north side of a four-story building, in the sunny strip by the garbage cans, in pots on the third-floor porch and on the windowsills in the winter.

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Hold the Salt
by Beth Botts       #Environment   #Winter

Snow is beautiful to look at and it insulates plants from the coldest temperatures, but take care when removing it. Shovel early, shovel often, and apply sodium chloride with a grain of you know what. 1

Most of the harm from snow really comes from how we get rid of it. Time for a little rethink.

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.


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.

Summersweet ‘Ruby Spice’ (Clethra alnifolia) 2


Smooth sumac (Rhus glabra) 2

Deciduous Trees and Shrubs

• Apple serviceberry (Amelanchier x grandiflora)

• Northern catalpa (Catalpa speciosa)

• Summersweet (Clethra alnifolia)

• Cotoneaster (Cotoneaster species)

• Smooth sumac (Rhus glabra)

• Bald cypress (Taxodium distichum)




Mugo pine ‘Tannenbaum’ (Pinus mugo) 2

Evergreen Trees and Shrubs

• Chinese juniper (Juniperus chinensis)

• Creeping juniper (Juniperus horizontalis)

• Mugo pine (Pinus mugo)

• Blue spruce (Picea pungens)



Find more at the arboretum’s website: mortonarb.org


Chinese juniper ‘Maneyi’ (Juniperus chinensis)


Photo Credits:
1. Photo copyright Micah Young - istockphoto.com/youngvet
2. Photos courtesy of Bailey Nurseries


(From Chicagoland Gardening Volume XVII Issue VI.)


Posted: 02/22/12   RSS | Print


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