Saturday, February 7, 2009

Boulevards, Good for Growing Vegetables? Comments

The boulevard (area between the sidewalk and the curb, called the "verge" in Australia or "parking-strip" in California) can be the sunniest location on a Vancouver lot. Unless there are too many mature trees, there is a significant amount of space on the boulevard that could be used for growing vegetables. Some Vancouver gardeners do this, and I have some photos of their plots on a separate blog. However, the Guidelines for Planting City Boulevards from the City of Vancouver state:
  • Contaminants from the roadway may affect consumables, therefore vegetable gardening is not encouraged.
This problem is something to consider in "lane gardens" also. However, lanes get less traffic, and even some side streets get little traffic. Herbs may be a better choice than vegetables, since one consumes sparingly of them. Putting the vegetables in containers with good soil would avoid planting in soil that has been contaminated over the years. The guidelines from the City also state: "It is recommended that soil or compost be mounded up to 20 cm (8") above the level of the previous sod. This ensures that there is adequate soil for plants to root and that underground services are not disturbed." Creating a raised bed as the City recommends would mean that shallow-rooted plants would not take in the older contaminants. Flower lovers, like myself, could consider transplanting their flowering plants to the boulevard, freeing up space closer to the house for vegetables. In any case, these are guidelines, not strict rules, and we can be thankful that the City has taken an enlightened approach in allowing plants other than grass to be grown in boulevards!

Just how contaminated boulevards can be would be interesting to know. Lead is the contamination most often mentioned. In 1990 lead in gasoline was banned in Canada, so there could be some residual lead contamination along the roads with heavy traffic prior to 1990.

There are other particulates in the air from vehicle exhaust and from industry. With our recent snowfalls not melting for a long time, the deposit of particulates from the air is easy to see. Snow piles get particularly grey near busy arteries. I do not know how much danger these particulates in the air pose for growing vegetables.

Plants vary in what contaminants they take up. Here are some sources of further information:

"What You Should Know about Lead in Soil" published by the Ontario Ministry of the Environment

"Home Gardening in Lead-Contaminated Soil" published as a Niagara Region Public Health Fact Sheet, Fall 2005

Lead in Urban-grown Vegetables; research done at Cornell University using soils from contaminated areas of New York City

Uptake of heavy metals by vegetable plants grown on contaminated soil and their bioavailability in the human gastrointestinal tract

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