Date: Fri, 24 Jan 1997 10:17:12 +0100 From: steiger@iae.unibe.ch (Juerg Steiger) To: cp@opus.hpl.hp.com Message-Id: <aabcdefg351$foo@default> Subject: Re: cultivation of temperate Pinguicula
Oliver
The problem of vernalization (to early sprouting) is the crux of all
growers of plants of cool climate areas. In CPN 4/1:8-18 (March 1975) I
gave a double-side table with the cultivation temperatures of all known (at
that time) Pinguicula species of the temperate growth type.The ideal
dormancy temperature for the species you mentioned (P. grandiflora,
longifolia, macroceras) was indicated as (plus) 1C / 34F. After cultivating
these species nearly 30 years now I can only confirm this figure. Your
present fridge temperature of 6C is definitevely to high. At natural
habitats the earliest sprouting northern species are P. longifolia subsp.
reichenbachian, P. macroceras subsp. nortensis and lowland populations of
P. alpina. Their hibernacula beginn to spread and develop leaves already in
March/April. The other species come later. The latest species are P.
algida, P. variegata and alpine populations of P. alpina, balcanica,
leptoceras (mid-June). I have my (sub)alpine and (sub)arctic Pings in a
greenhouse which is cooled all the year as long as temperatures are obove
the freezing point, resulting in winter temperatures of (plus)1-4C (summer
maxima around 20C). If outside temperatures are below the freezing point
(we had now just 4 weeks with day maxima below 0C, night down to -16C) a
little heater prevents the plants from heavy freezing and keeps it around
-1 to plus 2C. The species requiring longterm freezing (P. algida and
variegata) are stored in a special freezer at -8 to -3C. If once a
hibernaculum has sprouted it must given the opportunity to grow - if frozen
it will perish. The consequence of early sprouting is early development of
winter buds (in July/August) which usually do not survive. The ecological
tolerance of northern cool climate Pings is rather small and it is
necessary to imitate as well as possible the conditions of natural
habitats.
Good growing! Juerg
___________________________________________________
Juerg Steiger, Institut fuer Aus-, Weiter- und Fortbildung IAWF
University of Bern, Inselspital 37a, CH-3010 Bern, Switzerland
Office: +41 31 632 9887 Fax: +41 31 632 9871
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