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Re: Re: HYB: Daylength independent

In Kentucky, Immortality, Again & Again, Lunar Whitewash, Feed Back, Total Recall, Renown, and a few others, including but not limited to my own All Revved Up, have bloomed in July, August & Sept.? Around a dozen do so in my garden.? Another dozen if we count seedlings.? 

Another very small group will occasionally rebloom in July if the temps are a bit cooler.?

I'd considered all of these daylight independent since shorter days are not required to trigger the bloom.? 

In the Checklist, these are the irises that are listed (once widely distributed) to rebloom in zones 4 and above.? Previously called Everbloomers or Continuous bloomers.? They do neither, but CAN bloom at anytime, unlike the cylce rebloomers.? 

Maybe "daylight independent" is not the correct term for what happens in my garden, but short days are not required to trigger this bloom.? 

These two groups have figured more heavily in my breeding in the last two or three years.? I anxiously await bloom season.? 

Regular rebloom, or cycle rebloomers, dependent on the cool period you mention, do not start rebloom before Sept. 15, or even Oct 1.? Our?killing freeze will be mid-october till Christmas, with Oct being the norm.? 

In all cases fertility and water are necessities.? 

Although I bought a wide range of older rebloomers when I moved out here,?only a select few are being moved to the reorganized?beds. I make no attempt to grow all of anything.???

I do have a good collection of newer rebloomers,?especially the ones registered,?and hope to be able to report on them in the coming year.? 

?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.?

Betty Wilkerson/Bridge In Time/Zone 6/Dreaming of another good spring.? "Only those who dare to dream can make a dream come true."? 

-----Original Message-----
From: irischapman@aim.com
To: iris@hort.net
Sent: Wed, 20 Feb 2008 8:20 pm
Subject: [iris] Re: HYB: Daylength independent

Date: Tue, 19 Feb 2008 20:07:06 -0500?
From: "Mary Swann-Young" <MryL1@msn.com>?
Subject: [iris] HYB: Daylength Independent?
Chuck -?
Do you have Again And Again? How does it do up there??
Sure acts like daylength independent here.?
Mary Lou, near Indianapolis, Z5?
I have Again and Again, and it does rebloom for me. Sometimes two?
periods of rebloom. But in late August.?
What does it do for you that makes it exceptional??
For me, in my climate the bloom sequence is MDB May 8th, SDB May 19th,?
?IB May 26th, TB start June 2nd. Then rebloom sequence is TB Aug 18th?
(either immortality or Queen Dorothy) followed by IB rebloom about?
Sep 10th. SDB rebloom starts about md October. Rebllom opposite?
sequence from spring bloom. Most SDB rebloomers start only a very short?
time before frost. Of course the daylight independent plants, Forever?
Blue, Blueberry Tart, Autumn Jester and Forever Violet just keep on?
going like the energizer bunny. Occasionally a few odd blooms from a?
couple of SDBs but just one stalk and then gone. Precious Little Pink?
(IB) will bloom end of July or early Aug and sometimes later as?
well. I understand that this sequence is not the same everywhere.?
I had been using the wrong term for the cold period that is required?
for blom. It is called Vernalization. Following is the Wikepedia?
entry for vernalization?
""Vernalization (vernalisation - British English) is the acquisition of?
the competence to flower in the spring by exposure to the prolonged?
cold of winter. The word vernalization comes from the Latin word?
bvernus,b meaning bof the spring.b?
Many temperate plants have a vernalization requirement and must?
experience a period of low winter temperature to initiate or accelerate?
the flowering process, or, as the case with many fruit tree species, to?
actually break dormancy, prior to flowering.?
One of the most important influences that temperature has on the floral?
transition is the vernalization response. Many plant species, including?
winter cereals such as wheat through to Arabidopsis thaliana, must go?
through a prolonged period of cold before flowering occurs. This?
ensures that reproductive development and seed production occurs at the?
optimum environmentally favorable time, normally following the passing?
of winter.?
Following vernalization, plants have acquired the competence to flower,?
although they may require additional seasonal cues or weeks of growth?
before they will actually flower.?
In the much studied model species A. thaliana the apical meristem must?
be vernalized in order to promote flowering. Vernalization of the?
meristem appears to confer competence to respond to floral inductive?
signals on the meristem. A vernalized meristem retains competence for?
as long as 300 days in the absence of an inductive signal. It is?
possible to de-vernalize a plant by exposure to high temperatures?
subsequent to vernalization.?
Some plant species do not flower without vernalization. Many biennial?
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). ""?
I had been doing some research and found a few interesting facts. The?
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. This involves?
the Meristem tissue (growing point of stem) changing from producing?
leaves to producing a flower stalk. In addition iris ( we are talking?
oncers here) need the winter vernalization to set bloom. That is the?
days with cooler weather , but not freezing as plant needs some?
biological activity). Then it needs the correct length of daylight to?
trigger bloom. (actually it is correct amount of night time.) Then it?
needs correct amount of biomass, usually involving rhizome size and?
number of leaves.?
The commonest example of daylight Neutral flowering given is Dandelions?
, they bloom whenever a plant reaches maturity.?
?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.?
Chuck Chapman?
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