Winter Tips For A Better Garden

Feb. 28, 2000
There is little actual gardening activity at this time of year, but a number of things we do outdoors right now can have a direct impact on the performance of our plants and garden when spring arrives. Several winter activities like snow and ice removal or the joy of feeding birds can have an adverse influence on the garden.

With the weather conditions this winter many homeowners know the value of calcium and sodium chloride (rock salt) for melting the ice and snow that has accumulated on walks and drives. Problems are not necessarily associated with these products but from the fact that ice melting chemicals are frequently over-applied.

If you use either of these chloride materials to melt ice, apply just enough to melt through to the surface below. Apply the material as the ice begins to accumulate so the salty water will keep more ice from forming.

There are various recommended application rates for ice melting materials. However the U.S. Department of Interior, Park Maintenance Division, recommends one-half pound of salt per square yard of surface as a safe rate for plants. Over the years I have come to interpret this as a total application per season. As a compromise you might be able to go with slightly higher application rates if most of the salty water runs off your property and into the streets. It's the salt water that enters the soil and has the greatest potential for plant damage next spring.

Excess amounts of either calcium chloride or sodium chloride in the soil will harm nearby grass, shrubs and trees. Sodium in rock salt will also damage the soil structure and make it more difficult for injured plants to recover. A safer alternative for melting ice might be to use garden fertilizer. Run-off water mixed with fertilizer will help plants and lawns as long as you don't use too much. Excessive levels will harm plants in the growing season. Fertilizers like 5-10-10 often contain muriate of potash and urea which do most of the melting. Any superphosphate in the fertilizer probably adds traction and skid resistance rather than any melting value.

Urea fertilizer is a good melter at temperatures down to 11 degrees F, and is best applied at temperatures between 25 and 30 F. Urea can be used at rates of 10 pounds per 100 square feet. A mixture of about 3 pounds of urea per 100 pounds of sand provides excellent ice melting as well as traction. Sawdust can also be used as a carrier for the urea and provides traction also, but remember that this material will stick to shoes and boots and you may track it indoors.

It is important to remember however that all ice melting materials, if used to excess, will add significantly to ground water pollution. Use only enough to get the job accomplished, and consider alternative measures when possible.

Once you have the ice and snow melted go indoors and enjoy the birds at your feeder. Recent reports however suggest that even your bird feeder, or the seeds used in the feeder, can have an impact on garden quality next spring. The greatest threat comes from a toxin that leaches from the hulls of sunflower seed. These seeds are very important food sources in most, if not all bird feed mixes.

This property of one plant being toxic to another called allelopathy. Sunflower plants and seeds have been studied for their harmful affect on various garden and field crops. Little is known about the specific compounds that leach from the discarded seed hulls.

Over the course of the winter and at the end of the feeding season next spring you should clean up the hulls and discard them either in the trash or compost. The few remaining seeds that are missed should not have any significant impact on plant quality. However, if the remains of several hundred pounds of sunflower seeds collect on the lawn or in a shrub bed you might see reduced plant quality next season.

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**Dr. Robert Nuss is a horticulturist at Penn State. He coordinates all extension horticulture programs. He has bachelor’s, master’s, and doctoral degrees in ornamental horticulture and has been on the Penn State faculty since 1966.