Robert Bourchier's abstract from the Biology and Biological
Control of Established Invasive Plants in Canada session: Biology
and Potential Spread of Invasive Knotweeds in Canada: the Largest
Female in the Old World is moving to the New
knotweeds, including Japanese Knotweed, (Fallopia
japonica), Giant Knotweed
and their hybrid cross Fallopia
x bohemica pose a serious
threat to Canadian habitats. They form dense monocultures that
eliminate native species, threaten biodiversity, cause significant
damage to transportation and urban infrastructure, exacerbate
flooding and affect water quality for aquatic organisms... To assess
the potential spread of Knotweeds in Canada, known distributions of
the three invasive Knotweeds in British Columbia were overlayed on
provincial climate simulations and compared with published degree-day
and temperature thresholds for Japanese Knotweed. We conclude that
the degree-day threshold (2505 Degree Days) will limit Japanese knotweed to a
smaller area in BC than the minimum temperature threshold (-30.2°C).
Using results from known BC Knotweed sites, a precipitation threshold
of 735 mm/year was identified for Japanese Knotweed. In Ontario where
the existing Knotweed distributions are not as well documented, both
the minimum temperature threshold and limited degree days will
prevent large-scale invasions of Japanese Knotweed in Northern
Ontario. In Southern Ontario there is a large area (greater than 35%
of randomly selected sites) that is climatically suitable for
Japanese Knotweed. In contrast to BC, minimum temperatures will be
more limiting in Southern Ontario than the degree day threshold. The
precipitation threshold of 735 mm identified from BC will not limit
Knotweed spread in Southern Ontario.
Japanese Knotweed is called
“the largest female in the old world,” because of the
huge biomass of a single clone introduced to Britain and the European
mainland, which has spread asexually to become one of the major
invasive plants in Europe.
Home at PINICOLA
Report Ontario Knotweeds! Test a
At the "Biology and Biological
Control of Established Invasive Plants in Canada" sessions, held
in Ottawa on Saturday, 18 October 2008, Robert Bourchier, Research Scientist for Biological Control, Agriculture and AgriFood Canada-Lethbridge Research Centre, gave a
paper in which he presented a climatic model (based on degree day
values, overwintering temperature thresholds, and precipitation data)
for how far north in Ontario Japanese Knotweed, (Fallopia japonica
-- formerly known as Polygonum cuspidatum, and locally
"Bambooweed") might spread, if it were to become a serious
invasive here, as it is in New York, just south of Lake Ontario.
didn't have any current distribution data for Ontario, so we offered
him the BMNHC records of the species, and Mike Oldham contributed the
records he has, which we've mapped below.
Giant Knotweed, Fallopia sachalinensis, is also known from southern Ontario, most commonly in SE Ontario, though seems much less
common than F. japonica. As far as Mike Oldham (NHIC botanist) knows, Fallopia x bohemica, the hybrid between the two,
is not known from Ontario,
but is expectable based on the presence of the parental species and its occurrence in nearby jurisdictions (and quite likely
overlooked due to its similarity to F. japonica).
In the BMNHC records, most of which are driveby observations, we haven't distingushed the different kinds of Fallopia,
though we also haven't noted any particularly "giant" stands.
Many of the smaller Polygonum (e.g. Polygonum aviculare group) are also called Knotweeds; we're only concerned with the Fallopia species here..
There's a Key to the Identification of Invasive Knotweeds in British Columbia
which has good photographs of all the invasive species found there (also see the wikipedia article). This description of the invasiveness is modified from the text of the BC key:
'Escaped ornamental' is the term most often used to explain the widespread occurrence of invasive Knotweeds.
Since arriving in the 1800's their conspicuous, late-season flowers, handsome foliage, and striking height have made them
highly sought after by gardeners & landscapers. After a time, these hardy, persistent denizens escape their manicured
environs to colonize roadsides, lakeshores, fields, and meadows, but in New York & BC they spread most aggressively
along rivers & streams, where flooding & erosion dislodge rhizome fragments, which become the source of new infestations as they
lodge and root into favorable downstream niches. Even large segments of rhizome can float long distances in fresh water, and plants can
reliably regenerate from less than 2 cm of rhizome.
Now we're soliciting records of colonies of this unmistakeable species complex
Reports of stands away from cultivation, that
have survived on their own for some years (as indicated by their
size, or by knowledge of how long they've been present), would be
most valuable. The difficulty with the climatic model, and with current
knowledge of the species' distribution in Ontario, is that the limit
seems to fall in the "neck" of the province, along the
Ottawa Valley and southern Algonquin Park (though we've also received a few urban records from Thunder Bay). So records of occurrence
north of Hwy 7, and especially north of Hwy 60, on the Huron shore, the Bruce Peninsula, Manitoulin Island, and north are most valuable,
but records from anywhere will help to fill up the map, and accounts of the failure of the species to thrive in any area are also valuable.
can send records, or suggestions of who might know of stands, to Fred Schueler
-- clip the following form, paste it into your e-mail, and fill it in (you can also phone (613)258-3107). Any further comments, discussion, or photos are also welcome.
SUBJECT:Report of Japanese Knotweed in
Ontario or Quebec
County and Municipality:
Location or street address:
Latitude & longitude from GPS, or UTM from a topo map (if available):
Size of stand (approximate length, width, & summer height, approximate number of stems if the stand is small):
Is the stand cultivated in a garden, around a homesite or lawn, along a roadside, on a riverbank, meadow, woodland, disturbed ground, railway embankment, lakeshore, margin of tilled fields, or remote from human activity? (delete those that don't apply):
General surrounding habitat:
Date of the present observation, and how long has the stand has persisted, or how long you have known of it?:
If your name and telephone number, or other contact information, aren't in your signature file, be sure to include them in the message.
If eventually as we look at genetics of the invaders we may contact observers and ask them to send plant material.