As winter sets in, and the potential for ice and snow increases, be ready with deicing supplies for walks and driveways. Prepare now for freezing temperatures.
Properties should be beautiful and serve homeowners’ needs. Above all, they must be designed for safety. And one often overlooked consideration I always take into account when designing paved areas on clients’ landscapes is winter safety.
Walks and driveways of bricks, stones or pavers should have rough surface textures, not polished or glazed, offering traction in winter. Asphalt shouldn’t be too smooth when sealed, put a broom finish on concrete, unless it is an exposed crushed gravel aggregate paving without a smooth finish.
Many products are used to keep people and vehicles from slipping on icy surfaces including sawdust, shredded corn cobs, peanut hulls, fine ground bark, gravel, coarse sand, cinders, perlite, vermiculite, straw, wood chips -- virtually anything that provides traction. Materials listed above are environmentally friendly. These anti-skid agents do not dissolve in water, are reusable and can be swept up and used again. After winter, rake leftover traction materials into the lawn, cultivate into planting beds, and incorporate organic material into compost piles. These products won’t harm plants.
The most effective anti-skid agents are coarse sand or tiny (1/8 to 1/4 ") crushed gravel, available at building supply and home improvement centers. These are among the easiest to sweep up and reuse but useless when wet and frozen. Keep them dry.
In combination with anti-skid agents, salt further enhances traction by melting through ice. If ice is thick, salt will loosen it so it can be shoveled. You must have patience. It takes time for salt to melt through the ice.
Rock salt (sodium chloride) is a mined native salt, best known of all ice melting agents. It works fast and melts to plus 20 degrees Fahrenheit. Coarse crystals can be broadcast onto pavements by hand or with a spreader. Very few plants tolerate sodium chloride in their root zone. This one has the most negative impact on plant growth. Apply at a rate of 2 to 4 pounds per 100 square feet.
An alternative salt is muriate of potash (potassium chloride), a fertilizer ingredient. Used as recommended, it melts ice, won’t hurt plants but is bad for aquatic life. Don’t use where it will runoff into rivers and streams. It melts to plus 25 degrees Fahrenheit. Although slower working than rock salt, results are superior. Apply at a maximum of 3 to 5 pounds per 100 square feet.
Urea, synthesized from ammonia and carbon dioxide, is a plant nutrient too. It’s effective to plus 25 degrees Fahrenheit. Its downside is that runoff into rivers and streams promotes algae growth and it works slowly. I consider urea a nitrogen source in fertilizer rather than a deicer. Urea, phosphorus and potassium can runoff into plant beds, and now is not the time to fertilize. Never use a complete fertilizer as a deicer if there is a possibility of this happening.
Calcium chloride is a salt. Its advantage is speed but it is damaging to plants. It melts faster than other salts and is effective to plus five degrees Fahrenheit. Only use if you cannot find magnesium chloride or when time is critical.
Magnesium chloride has been used professionally for years. If speed and efficiency are important, try it. I like its safety record. Used as recommended, it won’t harm plants, is non-corrosive to metal and effective to minus 13 degrees Fahrenheit. You’ll use less product applying it at a rate of 1 to 2 pounds per 100 square feet.
The time it takes for salt to melt ice varies widely. It depends on factors such as solubility; size and shape of deicer particles, temperature, traffic, and how long it stays concentrated enough to be effective. Store salt in watertight containers like plastic trashcans. All salts except magnesium will corrode metal. If a little is good, more is not better. Over-applied salts threaten plants and when used to extreme measure, can damage concrete and mortar.
If you use salt, help your plants survive by
• Planting trees and shrubs twenty feet from roadways that are salted,
• Not shoveling snow from salted walks onto plants,
• Making sure there is good soil aeration helping salt percolate through soil,
• Irrigating with six inches of water in spring (an inch a day in the morning) if not enough rain; and
• Keeping salt sensitive plants like azaleas, crabapples, crapemyrtles, dogwoods, forsythias, American hollies, maples, rhododendrons, sweetgums and yews, as clear of paving as possible.
For more information on this subject, contact your local cooperative extension service, www.csrees.usda.gov/Extension.
Another safe deicer is CMA (calcium magnesium acetate). This is a slow acting agent effective to plus 25 degrees Fahrenheit. Primarily available at hardware and janitorial supply stores in 50-pound containers, this corn-based product is used to deice airport runways and bridges. It will not harm plants or paving.
I advise using deicers in conjunction with skid-proofing agents. Anti-slip materials can keep surfaces safe long after salt melts and will remain when temperatures hover around freezing. As soon as salt is dissolved, precipitation quickly washes it away. It’s only effective when melting ice from above or spreading a layer on surfaces prior to a snow or ice storm.
When ice and snow threaten, materials don’t stay in stock long. Stock up now or when you need a deicer you might have to purchase aquarium gravel.
© 2012, Joel M. Lerner