Friday, March 13, 2009

Hedera helix

Please don't plant this; it's invasive!

[Photo: Hedera helix foliage.]Hedera helix, known in English as "English ivy" or "common ivy" and in French as lierre grimpante, is an evergreen climbing perennial native to Europe. Unfortunately, in Toronto it is invasive. Invasive Exotic Species Ranking for Southern Ontario says it is a Category 3 Invasive: "Exotic species that are moderately invasive but can become locally dominant when the proper conditions exist." The City of Toronto's Urban Forestry Service recommends not planting it.

[Photo: Hedera helix blankets a front yard in Toronto.]This photo of English ivy completely covering a front yard in Toronto shows why this is a popular plant (how many ways are there to have a green "lawn" all year around in Toronto) but also why it is a problem. Native plants are going to have a hard time pushing up through this; the ivy also has an edge because it is evergreen, unlike most native plants around here. According to the Plant Conservation Alliance (US), when English ivy climbs trees it can actually kill them.

English ivy produces berries; birds eat the berries and spread its seeds. So this is not an easy plant to contain.

I can certainly understand the temptation to grow English ivy; it is pretty, and I almost bought some myself last year before I learned about it. Now I think it's just not worth the risk, especially when there are many many species native to Toronto you could grow instead.

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