It's been a depressing winter, not to mention the usual ice and cold. Financial and political solutions are hard to solve, so let's deal with the one we can at least affect: ice on walks and driveways.

It's been a depressing winter, not to mention the usual ice and cold. Financial and political solutions are hard to solve, so let's deal with the one we can at least affect: ice on walks and driveways.

There are several approaches, none of which will work perfectly at all times. One can try to keep water from freezing into a sheet of ice. One can try to melt the ice that's there. Or one can cover the slippery spots with something gritty to provide some footing.

The bottom line

The best ice-melt to use is probably calcium chloride -- though plain old salt, sodium chloride, is cheaper. Sand, gravel and kitty litter are most useful when it's already a sheet of ice. Now to the gritty details.

Keep water from freezing

Dissolved salts lower the freezing point of water. If water can't freeze, it stays liquid and non-slippery, and then evaporates when the air is clear.

The usual ice-melt chemicals are sodium chloride, potassium chloride, calcium chloride, magnesium chloride, urea, and fertilizer. Prices vary, as do each of their chemical properties.

The concentration of each chemical determines how much it will lower the freezing point of water. For instance, a 10 percent solution of cheap sodium chloride will lower the freezing point only to 20 degrees Fahrenheit.

However a 23 percent solution can lower it to minus 5 degrees Fahrenheit. A 26 percent solution will lower it to minus 26 degrees Fahrenheit. In other words, a sprinkle of table salt won't help much.

Calcium chloride is much more effective and lowers the temperature to about minus 25 degrees Fahrenheit. It comes in pellet form and is hygroscopic (i.e. it absorbs water and converts to a liquid). Magnesium chloride is similar.

Damage to plants, concrete

The real problem is from a high concentration of chemical left in the soil. Most damaging is sodium chloride. And although a little calcium and magnesium are useful for plant nutrition, high concentrations of their salts will burn as well. It depends on how often you have to melt ice during the winter.

Urea and 5-10-5 at low concentrations may be less harmful to plants, but they don't lower the freezing point enough, and so are not useful.

The way to mitigate all salt damage to plants is to flood the soil with water in April. Wash them out of the topsoil using the sprinkler or a hose, especially the sodium chloride. The others can just be heavily diluted and washed deep into the lower layers of the soil, where they can supply their minerals.

With concrete, the main problem is the salts may cause small cracks. Repeated freezing and thawing of these widens and extends them. It's very difficult to control. There are also less corrosive ice-melts containing acetate with salts, but they are only available to professionals.

Winter requires true grit

Gritty substances form an abrasive surface, which temporarily helps prevent slipping. However, they freeze into the next snowfall. Ashes are also good. Being dark, they absorb the sun's heat and therefore also melts ice.

Keep walks as bare as possible. Then less salt will be needed to melt what's left. Some recommend putting calcium chloride on before the snow starts to help melt the bottom layer and ease shoveling.

In a real pinch, like just before a party, you can lay long strips of cut-up old carpeting to make a path in freshly fallen snow.

Unfortunately, all these, both salts and abrasives, track a real mess into the house. Perhaps consider guest slippers by the door (like in Japan and Maine). Or a rug: 6 feet long is recommended for good foot-wiping.

Ruth S. Foster is a landscape consultant and arborist. More information can be found on her Web site: www.mothersgarden.net.