Re: CULT: growing degree days

Degree days info could possibly be usefull. Daylily people make use of it.
Ther is of course variation between pcultivars. 'Rosalie Figge' was able to keep growing for me in greenhouse with temps consistently above 40C during day.
In warn climates I suspect flower bud diferentiation occurs when temperatures drop where as in colder climates it occurs when temperatures warm up. I'm using night temperatures here. Lloyd Zurbrig was alwasys of the opinion that I got earlier rebloom them him because of the cooler night temps I got compared to him. 

Chuck Chapman

Date: Tue, 02 Sep 2008 10:58:58 -0400
From: Linda Mann <lmann@lock-net.com>
Subject: [iris] CULT: growing degree days

I wonder if growing degree days used by the Climate Prediction Center
might be useful to look at for sorting out temperature growth responses
in iris.  Not that corn is anything like iris...

Chuck, you mentioned that iris stop growing at 102oF - I wonder if that
is true for all species or if some stop "appreciable" growth at lower
temperatures?

<A corn growing degree day (GDD) is an index used to express crop
maturity. The index is computed by subtracting a base temperature of
500F from the average of the maximum and minimum temperatures for the
day. Minimum temperatures less than 500F are set to 50, and maximum
temperatures greater than 860F are set to 86. These substitutions
indicate that no appreciable growth is detected with temperatures lower
than 50 or greater than 86.>
- --
Linda Mann east Tennessee USA zone 7/8
East Tennessee Iris Society <http://www.DiscoverET.org/etis>
Region 7, Kentucky-Tennessee <http://www.aisregion7.org>

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