Archive for Thursday, December 20, 2007

Green thumb

December 20, 2007

Horticulturists usually wait until symptoms appear in the spring to talk about salt damage in the landscape. So why am I bringing it up now? Because we can prevent the injury:

The de-icing salts that we apply to our sidewalks and driveways are the source of much of the damage.

Warmer temperatures and more precipitation will wash the salt from concrete and asphalt surfaces into nearby lawns and landscapes and into storm drains. We can make better choices about what products we use and apply only the minimum needed to melt remaining ice. We also can make better planting choices in proximity to surfaces that require snow and ice removal.

The best option for snow removal is with a shovel or blade, but I know it is not always possible. Manual snow and ice removal is hard work, and shovelers should remember to take plenty of breaks and keep safety in mind.

Apply de-icer after shoveling is complete and only if there is remaining ice. Salt is not necessary on already wet surfaces, unless you're pretreating surfaces.

A visit to local retailers offers a few options of de-icers. You may have to turn the bag over to find the contents, but take the time to look even if the front of the bag deems the product "environmentally friendly." De-icers are not regulated, and no de-icer is truly safe for the environment.

Look for calcium chloride instead of sodium chloride. Although this chloride still causes some damage, it is considered the safest in its class. If available, calcium magnesium acetate (a salt-free product made from limestone and acetic acid) is a better option.

Most importantly, keep quantity in mind when using de-icing agents. Without naming names, there are multiple places around town where salted sidewalks are as white as the snow-covered ground nearby.

There is no fear of slipping on this crusty concrete, even for those in less-than-practical shoes.

How much salt does it take to melt the snow off of a sidewalk? The best bet is to apply de-icers sparingly and check back a short time later. You can apply more salt if necessary. Too much of a de-icing agent actually makes it less effective.

Fertilizer and urea are alternatives, but they burn plants in large amounts. Sand and cinders are not toxic to plants, but they pile up along curbs and on top of the soil and may be difficult to remove. Cat litter works similarly to increase traction - but please don't recycle it from the house.

Any product applied to concrete or asphalt will eventually wash into stormwater drains and leach into groundwater - staying in our water cycle and disrupting the natural ecology of our water systems.

Salt also damages concrete, especially new pads and walks, by increasing freeze and thaw cycles.

Salt spray along street easements is unavoidable - plant accordingly.

Symptoms of salt injury include browning and witches' brooming (small proliferations of growth). If you see these symptoms on plants near where you use de-icers, consider re-landscaping. Salt is highly toxic to all plants.

Plants to avoid near heavily salted areas: Basswood (Linden), white pine, red maple, sugar maple and Kentucky bluegrass.

Plants that are more tolerant of salt include gingko, Japanese tree lilac, birch, red cedar, red and white oaks, fine fescues and rugosa roses.

Even if plants do not exhibit signs of salt injury, high levels of salt in the soil increase plant stress, making them more vulnerable to insect and disease problems.

Increasing organic matter content and watering by hand when the ground thaws will help to leach salt out of the soil and away from plant roots.

The bottom line: Keep the lawn, landscape and environment in mind when cleaning your sidewalk this winter.

- Jennifer Smith is the Douglas County Extension AgentHorticulture for K-State Research & Extension. She can be reached at 843-7058 or smithjen@ksu.edu.

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