Invasive
Species – Aim for More Canadian Content
Catherine
Kavassalis for the Oakville Horticultural Society (Dec. 2005)
This past summer a
strange plant appeared in my yard. It looked like an orchid. I often let such
oddities grow until I can determine them to be friend or foe. Sure enough, its
August bloom verified that it was indeed an orchid, Epipactis helleborine.
“This is a diploid, perennial, multiflowered, often multistemmed,
wasp-pollinated, self-compatible, hermaphrodite terrestrial
orchid,” (quite a mouthful from the American Journal of Botany. 2001;
88:1409-1418 http://www.amjbot.org/cgi/content/full/88/8/1409).
It was first reported in 1879 in
Syracuse
,
New York
, but has now has spread across
North America
. According to the Global Compendium
of Weeds, it’s a foe, (http://www.hear.org/gcw/index.html).
Now you need to know that I adore orchids and spend the winter months
tending my small collection, so I did not yank it out. Many of us allow invasive
plants into our gardens. Some we woefully regret, others seem to stay within
their allotted confines in our particular microsystem. This summer, Fine
Gardening published a fun and useful article entitled “Plants I wish I
never planted” (2005; 103:22-32), in which they flagged a number of potential
gardening nightmares, including the indomitable goutweed, Aegopodium
podograria. I spent three years hand picking this lovely prowler out of my
yard. Aggressive plants like goutweed, however, can present more than a garden
chore.
Goutweed or Bishop’s weed is an example of an exotic garden import that
is spreading beyond the confines of individual properties and beginning to
dominate forest floors, just as purple loosestrife, Lythrum
salicaria, (another garden escapee) has spread into our wetland meadows.
As gardeners, we need to be aware that our plant choices may have direct
impact on the environment and the native species around us. Aggressive
foreign species that displace native species and destroy food supplies for local
wildlife should be removed or somehow constrained.
As I was researching this article, I discovered that my yard harbored
quite a few plants on the “Most Unwanted” list. For instance, I need to turf
some bush honeysuckle from my yard. Lonicera
japonica as well a L. maaki, L.
morrowi, L. tatarica and L. xylosteum
are now deemed Catergory 1 Invasives,
according to the Ontario Chapter of the Society for Ecological Restoration. This
organization has created lists of invasive plants based on their impact in our
region and prioritized the need for control. (http://www.serontario.org/pdfs/exotics.pdf).
Environment
Canada
has also produced lists for nationwide concern. They prioritize removal of
Common buckthom (Rhamnus cathartica), Garlic mustard (Alliaria
petiolata), Glossy buckthorn (Rhamnus frangula), and Leafy spurge (Euphorbia
esula), (http://www.cws-scf.ec.gc.ca/publications/inv/cont_e.cfm).
From my own observation of nearby
Joshua
Creek
, all of these, and garlic mustard in particular, are serious local problems.
The world is changing. For good or bad, it is botanically homogenizing. At
least 27% of vascular plants in
Ontario
are now aliens. I have personally contributed to this change. (My gardens could
not be shown on CBC – insufficient Canadian content.) While we hope that the
foreigners we welcome into our beds will bring us joy, we must be wary lest they
become interlopers. When they begin appearing next door, it may be time to toss
them out. So, I am going to sigh as I say goodbye to my Oriental bittersweet (Celastrus
orbiculatus) and then smile merrily as I replace it with its cousin, American
or False bittersweet (Celestrus scandens).
As you plan your new acquisitions for the spring, think Canadian.
May toads nestle in your flower beds and help you tend your beauties in
the spring.
To
learn more about invasive plants here are some other websites to visit: