D. linearis:
I don't have any trouble at all growing this species. For soil, I use
grey 'play sand', peat moss, vermiculite, and perlite (about 2:2:1:1 ratio).
I think the 'play sand' is probably limestone. Temperatures here have been in
the low-90's for the past week and it hasn't rained for a week and a half.
The garbage-can of rain water is nearly empty. Guess I'll have to start
using tap water for the first time in nearly a year.
Hope this doesn't stress the plants too much. D. linearis produces a
hibernicula and goes dormant late September - about a month before cold
weather hits here. At that time, I store the hibernicula in barely damp
vermiculite and keep it in the fridge.
P. valisneriifolia and P. alpina:
Jurg Steiger wrote a good article on temperate Pings in CPN, Vol. 4, #1.
P. vallisneriifolia is native to Spain. The following is from Jurg's
article:
"Grows in the marly crevices of shady and soggy vertical or overhanging
limestone rocks. No rain in summer, wet and mild winter (temps usually
above the freezing point). Leaves very long up to 30 cm. Develops
off-shoots (runners). Flowering May-July."
This species doesn't like to be exposed to direct rainfall.
Now for P. alpina:
"From Scandinavia and different higher mountain chains of Eurasia (0-4100m).
Grows in different kinds of bogs, on springy slopes and other moist places
including wet bluffs and rocks. Habitats may vary from shady to full sun.
Occasionally associated with P. grandiflora, ..., P. vulgaris, but
advancing into dryer places than those. Perennial roots. Flowering
May-August. Winter period lasts 7-9 months, growing season 3-5 months."