Re: HYB: Daylength independent
Thanks so much for digging up data, Chuck. Interesting stuff.
species have a vernalization period, which can vary in period and
temperature. Typical vernalization temperatures are between 5 and 10
degrees Celsius (40 and 50 degrees Fahrenheit).>
This temperature range matches my perception (sorry, no data, just
casual observation) of temperatures needed to trigger fall bloomstalk
production in "cold climate" rebloomers here, both those that seem to
bloom independent of daylength and those that only rebloom in the fall.
Some cultivars rebloom much earlier in the fall than others, depending
on when that period of cold comes - most years, we don't get
temperatures that cold until August. It takes about 6 weeks after that
for blooms to open.
Flower Bud initiation in iris typically sets the end of August in
Japan (Where the research was done) with daylight temperature was
average 26C. Thus probably earlier in cooler climates. > [that's about
80oF is about the daytime temperature when nighttime temperatures drop
to the 40s and 50s at night.
Temperatures are erratic here, so we may get only one or two nights that
low with an early cold front, but that seems to be enough to trigger
<Immortality can sit in my garden with mature size rhizomes and lots
of leaves, but doesn't bloom until Mid to late August. This would
suggest that it is not daylight independent.
Forever Blue does bloom whenever a rhizome reaches maturity.
The peculiar thing about IMM is that she will make stalks thru the
summer <IF> we get a cool night or two (doesn't happen every year), but
most other rebloomers don't do that.
Chuck, can you come up with a theory that might explain IMM's different
behavior where you are compared to here?
My guess it's some kind of interaction between daylength and
temperature, but I can't figure out how it might work.....
Maybe she has to have longer days to keep blooming than you ever get in
A few other cultivars are 'summer' bloomers here - BELVI QUEEN, VIOLET
MIRACLE, TEA LEAVES, but these three seem to require more of something
(longer? less erratic? cool periods, less erratic moisture? ??) than IMM.
Wish I had been keeping temperature/rainfall records, especially the
year when IMM bloomed repeatedly.
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>
American Iris Society web site <http://www.irises.org>
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