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Re: CULT: a more common problem
  • Subject: Re: CULT: a more common problem
  • From: Chuck Chapman <irischapman@aim.com>
  • Date: Sun, 05 Sep 2010 09:48:18 -0400


I got some insight into bloomout this year.  I have been keeping temerature records for some time and co-ordinating it with rebloom. Some very interesting information was learned from this.

Bud set, that is the  diferetiation of  the growing tip (apical Mersitem)  from producing leaves to producing  flower parts has a very specific temerature requirement. Once bud set occurs, the plant increases now start to grow. This is a a result of removal of  the  growth repression control (apical dominance)  that is exerted by the growing tip. Once it is in the stage of flower bud production this repression no longer occurs.

Temperature requirement is that minimum night temperatures are in 15-21C or 59-70F range for about five nights in a row.

Last year we had cool nights and did not get the required warmth at night needed for bud set (at least not for most cultivars)

This year there was lots of bloom in spring but no increases, so lots of bloomout. Obviously there was a secondary bud set as a result of  winter vernalization, but it didn't  trigger  growth of increases( or increase set) the same way that  summer temperatures did.

With you the problem would be having cool enough  nights as versus my problem of having warm enough nights. But same result.

 If you have a weather station near you  you could check on minimum temeratures. Or I could look at it. Just let me know of weather station nearest to you with recorded temerature data.

The critical temperature varies from cultivar to cultivar, depending on it genetic inheritence from species.

Chuck Chapman

-----Original Message-----
From: Donald Eaves <donald@eastland.net>
To: iris-photos@yahoogroups.com
Sent: Sat, Sep 4, 2010 10:32 pm
Subject: [iris-photos] CULT: a more common problem

It's frustrating to see a seedling grow and increase well, then have all
those fans bloom without any subsequent increase. It's something a see a
lot. Here's one. The seedling put on five increases, then the seedling fan
and all those increases bloomed. No increase. I dug them out today and
they are all solid. No sign of rot, dry rot, pithiness - and not a hint of
any 'eyes' to make new increase. You'd think a seedling that had the
genetic code to put on that many increases to begin with would follow
through with more increases. Not so all too often. I've wondered if this
isn't similar to balding, but am not at all sure it's the same thing since
it seems to only occur in seedlings. In this case, as I often am, I'm
disappointed. The cross was Heart Stealer X (Childsong x Zerzura) - or
Heart Stealer X Feeling Sorta Blue since Elm Jensen registered the pollen
parent. It had a sibling I considered the best new seedling of a good crowd
this year for many reasons, but I actually liked the colors better on this
one (2nd photo). Sort of iris as an annual, I guess. But they aren't
supposed to be annuals. There are several more out in the patch that are
probably going be just like it. The shovel did its part after bloom,
attrition is adding to the thinning out among others. That's just the way
it works. It's just the attrition falls where I'd prefer it didn't all too

Any ideas on provoking those rhizomes into putting on some increase?

Donald Eaves
Texas Zone 7b, USA

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