winter hardiness

John Lonsdale
Sun, 27 Jun 2004 09:22:49 PDT
Tony A wrote "Most plants in the Florida panhandle have hardiness to at
least zone 6 and some further north.  Originally, many of these plants
resided in the Ohio or Delaware Valleys and were relocated during the last
ice age.  They never bothered to lose their winter hardiness."

But some of them did adapt to their new deep south environment such they no
longer are effectively 'hardy' in zone 6 even though their rhizomes may not
be killed directly.  Trillium underwoodii from around Chattahoochee and
Trillium decipiens from a little further north in Georgia are perfect
examples.  Their rhizomes are indeed 'hardy' but they have adapted to the
deep south winters and they put up leaves as early as December here in Exton
(zone 6b/7), pretty much irrespective of local climatic conditions.  They
seem to respond to a calendar - and of course here this new top growth is
rapidly trashed by temperatures below about 15F.  A couple of years of this
and they are no more.  It is interesting to note that Trillium lancifolium,
which grows in the same woods as T. underwoodii near Chattahoochee, has
learnt to keeps its head down longer, and so fares better here without


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