What's the answer to protecting plants while melting snow?
Which is better for plants and the environment, spreading sand or salt to melt snow and provide traction? You'd think the answer would be obvious -- sand is natural, chemicals aren't.
But it turns out that the obvious answer isn't the whole story.
What to do about making roads safe for people while not harming the environment is a debate that's been going on in Canada for some time. It's gotten more discussion in the US this winter because of all the snow in usually rainy Seattle.
To protect the Puget Sound, the city refused to use salt or chemicals on the roads and instead used sand. This annoyed many residents, who pointed out that the sound is a body of saltwater.
But Eoin O'Carroll's Bright Green Blog says that's not the whole story either.
This is an environmental discussion on a large scale, but it's also a subject with a micro effect on almost every gardener who lives where it snows.
If you use salt on your driveway or paved paths, here's some advice from garden expert Mike McGrath, given on the website of WTOP radio station of Washington, D.C., about how to use it correctly (and save some money, too.): Read the labels on those bags and cartons so you know what's inside. Often a product that touts a more expensive chemical on the front actually contains mostly rock salt -- bad for plants and soil -- with only a small amount of a "good" chemical.
Good chemicals? He recommends that you purchase products that contain ONLY magnesium chloride, potassium chloride, and/or calcium chloride.
However, Leonard Perry, extension professor at the University of Vermont, says that those chemicals can also be corrosive and may damage plants somewhat.
His suggestions for avoiding plant damage include mixing 50 pounds of sand with one pound of rock salt and using that instead of all rock salt.
Ah, but sand is a problem with wetlands. It clogs them up.
Some people suggest spreading kitty litter where you just need traction and not melting. (However, use the nonclumping kind and be aware that you'll be tracking it into the house.)
You may have heard that fertilizer spread on ice and snow won't harm plants and will melt snow. But that isn't a good environmental choice either, says Jeff Rugg of the University of Illinois Extension.
"It can also be harmful and some portions of it will wash into the storm sewers, fertilizing streams, and creating algae blooms and other problems," he explains.
When the plants you're concerned about are along a roadway, so that you have no control over what has been used as a melting agent, you may want to "erect burlap or similar screens near shrubs or hedges to keep this salt spray off plants," Dr. Perry says. " These especially are useful in front of evergreens."
But we know that salt harms the soil as well as plants. "Solutions to soil salt damage," he says, "include changing drainage patterns so plowed winter snow and salt run away from plants when melting." Then, "as soon as snow melts in spring, give the soil a thorough flushing with water to help leach these salts away from plants. "
Finally, here's another alternative: Hort-Pro On-Line Magazine in Canada gives a list of salt-tolerant plants, which includes a number of shrubs, trees, ground covers, and evergreens.
