Potamot de Hill

The species is relatively uncommon throughout a somewhat-limited range. Its rarity may be a results of poor seed production, seed dispersal or establishment abilities (Nepstad 1981 in NatureServe 2014) however its random appearance and disappearance in its habitat suggests a well-developed and active dispersal regime (NatureServe 2014). The species is most common in western New England, eastern New York and northern Michigan (Hellquist and Crow 1980 in NatureServe 2014). There are approximately 87 documented occurrences (post-1970 occurrences with specific locational information): Connecticut (1), Massachusetts (22), Vermont (27), New York (10), Pennsylvania (3), Ohio (4), Michigan (8), and Ontario (12), though it is likely there are over 100 occurrences scattered across the range (NatureServe 2014). According to Parks Canada Agency, there are between 28-35 sites for the species in Ontario and the most recent COSEWIC status update report (in 2005), estimated the Ontario population at 119,600 individuals, but this total uses data from only 12 sites so it is likely to be double this number. Trends in the number of individuals and occurrences are not known, it is likely to be undergoing a decline due to reduction in water quality since settlement, however several populations in Massachusetts and Vermont are extensive, with thousands of plants reported and (NatureServe 2014). The species is classed as globally 'Vulnerable' (note this is not the same as the IUCN Red List Category) by NatureServe (2014), however the populations in Canada are classed as 'Imperiled'. The Canadian Endangered Species Conservation Council (CESCC) also class the species as 'May be at risk' (for Canada only).
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