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Apply deicers properly to avoid damage to garden

THURSDAY, DEC. 10, 2009

We have definitely traded the tools of summer gardening for the winter shovels and deicers needed to keep sidewalks and driveways safe. As with gardening, the right tool used in the right way can make the job easier and safer. The right deicer used at the right temperature can mean the difference between slick and safe walks.

In general, a deicer works by generating heat as it dissolves or lowering the freezing point of water as it mixes with the liquid water molecules remaining in the ice or snow. This solution then penetrates the rest of the ice or snow around it until it reaches the walk or driveway. It then spreads under the ice breaking the bond between the ice and the pavement.

Different common deicers work at different temperatures. This means that as the temperatures drop below freezing certain chemicals lose their effectiveness while others continue to work. Some of the common deicers available on the market and their lowest effective temperature include:

•Sodium chloride (rock salt): 20-22 degrees.

•Urea (fertilizer): 15 degrees.

•Potassium chloride: 12 degrees.

•Magnesium chloride: 5 degrees.

•Calcium chloride: 25 below zero.

Like the garden chemicals we use in the summer, winter deicers have to be applied properly to be effective and avoid damage to concrete and landscaping.

Rock salt has been a popular deicer for years because it is easy to get and relatively inexpensive. It however can cause extensive damage to plants near where it is applied, causing leaf and root damage that won’t be noticeable until the spring or summer. The dried-out leaves and stunted growth habit can often be mistaken for some other malady that late in the year.

Urea is a common component of the fertilizers we put on our lawns and gardens. As the bag clearly states, putting on too much will burn the plants. This is true in both the summer and the winter. Runoff from the walk you are deicing can easily damage nearby plants and lawns. Both rock salt and urea lose their effectiveness as temperatures drop into the lower 20s.

Potassium, calcium and magnesium chlorides are newer and more environmentally friendly deicers that work at much lower temperatures. The potassium in potassium chloride can actually benefit root development as it is a major component in fertilizer.

The best way to reduce potential problems with deicers is to use them judiciously and apply them with care. Shovel your walk first and then apply only enough deicer to get the job done. If you want to be even more environmentally friendly add a little sand on top of the deicer to add some traction.

Both sand and the newer deicers can be tracked into the house and cause a mess or damage to floors. Put out a good, thick door mat or boot brush so people can clean their shoes. Maybe this is the time to start the Japanese tradition of leaving shoes at the door. Warm, fuzzy slippers anyone?

Pat Munts is a Master Gardener who has gardened the same acre for 30 years. She can be reached at

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