soil temperature variation with depth in a bulb garden
Peter Taggart (Fri, 22 Nov 2013 11:13:32 PST)

apologies in that I missread this book this morning.
The correct information is:
dormancy in 'dutch ' Iris is initiated by temperatures greater than 17 C.
Optimum temperatures for initiating flowering shoots are 8 to10 C for 6 - 9
weeks, depending on the variety
Page 84, Ornamental Geophytes

Peter (UK)

On Fri, Nov 22, 2013 at 4:21 PM, M. Gastil-Buhl <gastil.buhl@gmail.com>wrote:

Peter has been doing my homework for me, reading that thick textbook.
He writes:
"Temperatures less than 17 C apparently act as chilling for certain
'dutch' Iris for example."