Winter Chilling of Heat-loving Plants
Mon, 01 Oct 2007 19:24:55 PDT
The replies in the thread "Cardwell lily" remind me of a possibly 
relevant experience I had with Ipheion sellowianum. (That's not the 
accepted name these days, but you guys know what I mean; little 
yellow ipheionish thingy.)

I'd always overwintered it in a covered coldframe, and it came 
through very nicely year after year, apparently fully hardy if 
protected from winter wet. About 10 years ago, it was exposed to 
considerably more winter cold than usual. I don't remember if it was 
a harder than normal freeze or I forgot to shelter it.

After that it went completely dormant. Every spring I would check and 
there would be sound bulbs in the pot, but no signs of life. The 
smaller bulbs faded away, but the larger ones the size of a pea just 
sat there, not dead but hardly living.

At some point, someone here on the PBS mailing list mentioned that 
some amaryllids have a fairly high heat requirement, so one spring I 
took the pot of dormant bulbs and put it just inside a glass patio 
door facing south, sitting in the full sun with the soil getting 
considerably warmer than it would out of doors.

This was followed quite soon by signs of growth and it's continued to 
grow actively ever since.

My interpretation of this series of events is that the plant went 
into a very deep dormancy because of the severe cold it experienced, 
and this dormancy could only be broken by considerable warmth. From 
an evolutionary point of view, it means that Ipheion sellowianum 
(native to summer-hot Japan) goes dormant during cold winters and 
doesn't resume growth until the weather is well and truly warm. It 
can't be fooled by mild spells during the cold months.

Some of the replies in the "Cardwell lily" thread suggested a similar 
situation: being a true tropical, if it gets too cold, it will be 
hard to awaken from the resultant dormancy, and lots of heat may be 
the trick.

Rodger Whitlock
Victoria, British Columbia, Canada
"Outside of dogs, books are man's best friend;
   inside dogs, it's too dark to read."
               -----Groucho Marx

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