P. vulgaris is not alpine but colline-montane-subalpine. In Ireland,
Scandinavia, Greenland, Iceland and Canada it is found also at sea level.
I doubt if it grows much further S in eastern North America than indicated
by Casper who really quoted all sites which were known from exsiccata of
all U.S. university botanical institutes 30 years ago. At the sites where
P. vulgaris occurs it is usually quite abundant and not easy to overlook.
If it would exist in southern sites I think some botanists would have
recorded it within the last hundred years. But detection of new sites are
always welcome!
The tiny and easily overlooked P. villosa is circumpolar and grows in
Sphagnum fuscum bogs, usually at sites where there is a mineralic ground
below the bog, not on pure Sphagnum bogs with water beneath it. In the last
30 years I tried several times to grow Scaninavian P. villosa in
microclimatically suitable subalpine Sphagnum fuscum bogs in Switzerland at
about 47 degr. N latitude, but I always failed. That's why I thought and I
still think it might be a long day plant which needs summer day lengthes of
18 hours or more. Nevertheless the southernmost sites are on Vancouver
island around 50 degrees N latitude which is far more N than New Hampshire
but not far more N than our Alps. May be the Vancouver plants are more
tolerant towards shorter day length than the Scandinavian ones
(southernmost sites at 60 degr. N).
P. alpina originated in the Himalayas from where it spread to N (Siberia)
and then to W and SW (Scandinavia, Scotland, Jura, Tatra, Alps, Pyrenees)
and therefore does not exist in the Causasus and its neighbouring mountain
ranges. It is not an originally northern species and therefore not
sensitive to the day length as possibly P. villosa.
Henusode Juerg
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