Winter Compost Piles (Street Side Left Behinds)



Regarding Compost Zone 5B.

1. Street side leaf pick up comes every year in late October here in Cambridge. Last year a large amount of product was left behind and is still sitting curb side in late Jan 2020. Is street side curb leafs a good idea to put in my compost pile? My concern is the salting done by the plows and if this effects the plant material.

Thank you


Thank you for contacting the Toronto Master Gardeners.

Fallen leaves provide food, shelter, and nesting or bedding materials to a variety of wildlife, as well as overwintering protection for a number of insects, all of which work together to contribute to a healthy yard. The soil itself is also a beneficiary of this autumnal gift of fallen leaves, as the leaves are essentially composted over time into nutrients that feed both the next year’s ‘crop’ of grass, but which also feed a vast number of microbes in the soil, which are actually the most important aspect of your soil, considering that all plant life in your yard depends on a healthy soil biology.

Salinity is when salt dissolved in water is present in the soil. Small amounts of salts occur naturally in soil but problems arise when too much salt accumulates. In fact, dissolved salts hold water in soil more tightly than roots can extract it. As a result, plants are not able to take up nutrients needed for growth.

In our colder regions de-icers and road salt are a major source of salt. Salt splashed from the roads may be deposited onto lawns, plant leaves or needles. The University of Saskatchewan College of Agriculture and Bioscience has an excellent article on Salinity: Salt Damage

Unlike animals plants are not able to excrete salt from their tissues and can only get rid of excess salt by shedding leaves and needles. Plant species vary in their tolerance to salt exposure. This website gives a list plants that vary in salt tolerance. For example, many herbaceous plants such as grasses adapt fairly readily to high salt levels.  Among woody plants, tolerance varies with the species. Plant species with waxy foliage or scaled, protected buds are generally more tolerant of salt spray.

Road salt is also known to affect soil quality. The sodium component in rock salt becomes attached to soil particles and as a result, displaces other important soil elements such as potassium and phosphorus. This results in an increase in soil compaction and a reduction in drainage and aeration.

My recommendation would be to not include the piles of leaves which were left at the side of the road during the winter in your compost.