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Re: Northern/cold weather hardiness

  • Subject: Re: Northern/cold weather hardiness
  • From: irischapman@aim.com
  • Date: Tue, 31 Mar 2009 10:41:08 -0400

I'm glad I've stirred up the hornets nest. It needs to be stirred.

It is hard to get a good list of cold hardy plants, particularly TB
plants. An article in recent AIS Bulletin on cold hardy TBs didn't
even mention any of the Canadian irs that have been introduced, and
there are a number of hardy ones, from current and past hybridizers.
The article even recommended about 4-5 plants introduced by Ghio. I
have tried over 80 of his beautiful and striking plants, only to have
about only 10 of these still surviving in my garden. Of these only
Liason would be classified as a good garden plant for me. Double Vision
may prove to be a good garden plant, but it hasn't finished it's five
year trial outside yet. Starring was recommended as a cold hardy plant.
I can keep it alive in cold greenhouse ( where I have a number of
tender TB's , including five Ghio plants) where I keep outstanding
plants with unique genetics, that I hope to pass on the genetics to
more hardy seedlings. Starring has only survived one winter here
outside, never two winters in a row.

Plants , particularly TBs will survive their first winter if planted
early enough in almost all climates. If they survive first winter they
will bloom well. But, and a big but, the bloom and the increase seen
on this plant, were initiated in garden where the plant came from. The
flower bud initiation seems to need certain conditions in order to be
set, including plant maturity and a temperature range above about 15C
and below 20C (roughly). If these conditions are not met, then you will
see a slow decline in plant over time. In addition, every winter is
different, leading to different survival. Thus the need for a 5 year
garden trial to see if it proves to be hardy in your climate. At times
I have thought I had found a hardy orange iris. These did well for
several years, only to have all of the plants disappear over an
unfavourable winter

Last year I had a lady from Yukon Territories (Canadian Alaska) wanting
me to send her plants in September, insisting that they would survive
for her, and that TB's did well for her. This led to a bit of
exploration. She had gotten some iris plants from a mail order house
the previous year. A garden place that imports plants, and then
reships them. Her iris plants arrived in early October, in a very dried
condition, in what I refer to as deep dormancy. She planted them right
away, the next day her garden soil froze up, and remained frozen until
spring thaw. They bloomed nicely for her in the summer. She was
convinced that this proved that iris TB plants would do well for her.
Of course they survived winter ,as they were in a dormant state, and
didn't dry out further in soil. These plants will in all likelihood die
this winter. They would not have been able to produce daughter plants
that were large enough and get temperatures they needed to bud set or
start increases. The survivors this year, won't make it past next
winter. I was able to dissuade her from ordering for late

I like to hear of what survives cold climate conditions, but only after
it has passed a five year trial, and still blooms well and increases
well. That is a good consistent bloomer , with good increase. If any
cold climate growers have this type of information of this type,
please forward it to me.

Humoreque does grow very well for me. Always blooms. Red Revival is a
Canadian historic, that is not only cold hardy, but reblooms like crazy
here, and is early enough in rebloom to rebloom in much colder

I breed more TB then SDB, but don't get near the number of hardy plants
with TB. I'm now getting a good base for breeding hardiness, with
beauty. Still, something like Garden Bride will constantly be over
looked in good growing areas. It is a very nice white, but not a Ghio
bubble ruffles, stand out at the ball type of iris. When trialed in
Loomis, it walked away with top spot, in a harsh winter. Everything
else suffered, while Garden Bride thrived. It had over 80 points,
trailed by a couple of Schreiner intros with point count in 60's. It
needed beauty, and bud count as well as vigour to get all of its
points. But when trialed in convention in Oregon, no one even looked

I have a couple of other super hardy cold climate plants, that may
also be hot climate tolerant. Buckskin Babe (2007) (an orangish tan)
and a plicata that is being introduced this year., Much like Tennison
Ridge, but improved in colour, branching etc, and it is very hardy, and
rot resistant. Borers also seem to avoid it. But again, something that
will be overlooked in convention gardens.

When breeding for cold hardiness, be sure at least one of your parents
are very cold hardy. Make crosses both ways. I personally suspect pod
parent will pass on hardiness more then pollen parent. If using a
historic, cross with a modern variety. Also note how plant goes into
fall dormancy. If it starts to die back before hard frost hits, it will
have better cold climate survival.

Chuck Chapman

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