Branched bartonia (ssp. paniculata) COSEWIC assessment and status report: chapter 8
Limiting Factors and Threats
The open sphagnum bog or fen habitat for branched bartonia is widespread in southcentral Ontario and there are potential areas that could have populations of the species. Two apparently suitable sites within the known Ontario range were investigated by the author in 1991; however, branched bartonia was not found. Another apparently suitable site within the range was investigated by the author in 2002; however, branched bartonia was not found at that site. Members of the Atlantic coastal plain flora, to which branched bartonia apparently belongs, are generally restricted to a rather small area of southcentral Ontario.
No imminent threats are known that would eliminate branched bartonia in the next several years; however, peripheral areas of two sites (Sites 5 and 6) are being taken over by the invasive shrub black buckthorn (Rhamnus frangula). This shrub is also present but not yet dominant in the open areas in the immediate vicinity of branched bartonia. Continued expansion by this aggressive invasive shrub could threaten branched bartonia at these two sites in the coming decades. At Site 2, where the species could not be confirmed in 2002, the population was located adjacent to a railway embankment. If this embankment were to be widened the site could be eliminated.
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