By Ken Lain, the mountain gardener
Mountain snow keeps the forest healthy and strong, but ice melt products used to control it in or near our gardens can be dangerous to humans and our plants. Pets and birds can also be hurt by these products. Here is the inside scoop on de-icers and how to use them safely this winter.
How Do They Work? Ice melt products attract moisture to themselves to form a liquid brine which generates heat that melts away ice and hardened snow. Each product must touch the pavement to become effective. Once on the pavement the brine can spread out and break the bond the ice has with the pavement. As the ice is loosened, it is easily shoveled away.
What to Look For – Every year there are more choices when it comes to ice melts. A lot of the choices are similar and differ only in the way each is marketed; with each product claiming to be ‘The Best’. 95% of all ice melts are made from one or a blend of five products. Typically blends are made to try and combine the best advantages of each chemical.
Urea – This very common early spring fertilizer also is effective as an ice melter. It will melt ice to 15˚F. Caution – too much can harm vegetation.
Sodium chloride (rock salt) – It’s effective and the least expensive to melt ice as low as 20˚F. It dries out icy surfaces, but is not as harmful to concrete as other products. It can damage landscape vegetation, and is very corrosive to metal.
Calcium chloride – This is your traditional ice melt. It melts ice down to -25˚F. It gives off heat as it dissolves, which very rapidly melts the ice, but if over-used it can leave residue corrosive to metal and damaging to vegetation. Magnesium chloride is becoming more popular than calcium chloride as it is less corrosive and safer on concrete and plants.
Potassium chloride – This de-icer works well when mixed 50/50 with rock salt. It will melt ice to temperatures of 12˚F. Although relatively safe, it can cause plant injury if over-applied.
Calcium magnesium acetate – This is a combination of dolomitic limestone and acetic acid (main compound in vinegar). It has little effect on plants and concrete but its performance decreases at temperatures below 20˚F. It works differently from other products in that it does not form a brine like salt products do. It helps prevent snow particles from sticking to each other on roads or walkways. It prevents re-freezing more than it melts ice, and tends to leave a slush on treated surfaces.
Are They Harmful?
Given the alternative of dangerous slippery conditions, the benefits of de-icers outweigh their potential disadvantages. All ice melts have the potential to damage vegetation, concrete, and metal. Moderate use combined with adequate rainfall and snow fall dissolves and washes enough of the product away to protect vegetation and hard surfaces.
Concrete Caution! – Damage to concrete occurs not from the effects of the salt, but from the effects of the freeze-and-thaw cycles of water. When the freezing point of water is lowered, the number of freeze-and-thaw cycles increases and the expansion of freezing water (hydraulic pressure) can exceed the strengths of concrete. This is especially dangerous for concrete less than a year old.
Natural Alternatives – Other, more natural, products can be used to treat icy sidewalks and driveways. Although they are generally less effective, they pose less harm to the environment and to pets. Natural alternatives like sand, sawdust, wood shavings, and kitty litter are mainly effective for their gritty, anti-slip qualities. They provide better traction for walking on ice but do not actually melt the ice. They do warm quickly under our high mountain sun and cause natural, fast melting. They often are mixed with ice melt products as a way to use fewer chemicals.
Ice Melt Precautions
> Wear gloves. Ice melts can irritate skin.
> Clear snow first, then apply product. Don’t try to melt everything.
> Do not use on new concrete that has not been fully cured.
> Do not over-apply. Follow instructions on the label.
> All products have some effect on the environment. Flush area with water if over-use is suspected or damage appears on plants.
Until next week, I’ll see you at Watters Garden Center.