Oncocyclus iris, was 1936 usda zones, US

Bob explains well about the "monsoon" rain pattern in the US Southwest.
Nevertheless, there are notable growers of Oncocyclus irises and their
hybrids in that region. I don't know if they give them special
protection against summer rainfall, though.

The Pacific Northwest, where I live, is a particular challenge to
growing these beautiful irises. I've acquired a number of the
"Regeliocyclus" hybrids, crosses between the sections Oncocyclus and
Regelia, which are a bit more amenable to winter damp. The only pure
onco I grow well is Iris kirkwoodii, which is just coming into flower in
the bulb house, where it is protected from rain and gets a very dry
summer dormancy. I have two other species that are just young seedlings
at present.

One problem with the Regeliocyclus hybrids is that many of them have
very tall stems that tend to fall over. However, I'm very happy with the
performance of 'Cythe', which has shorter, study stems, big flowers of a
form very like a true onco (with a showy dark patch on the falls), and
-- to my surprise -- is doing quite well in a raised bed without
overhead protection, even after one of the wettest winters ever recorded
here. I'm going to try more hybrids and even species. Growing the
species from seed is a very long process, especially because the seeds
don't break dormancy very readily.

Two years ago I enjoyed a Greentours trip in Azerbaijan and eastern
Anatolia where we saw a number of irises in nature. Most if not all of
them were in places where they experience snow in winter or at least
heavy snowmelt moisture in spring. I remember the great plantsman Fritz
Kummert, in a lecture, commenting that these irises and the bulbs that
grow with them can take an almost unlimited amount of moisture in spring
when they're at their peak of growth. Getting rain, rather than snow, as
they do here, their overwintering leaves can look pretty battered by
spring (partly because of slugs), but they recover quickly. If they
experienced damp along with warm temperatures, however, they might
succumb to disease. I've struggled with the beautiful and unusual Iris
paradoxa, but now that I've seen it in its native haunts, I have a
better idea how to grow it -- though I can't provide nearby ancient ruins!

Jane McGary

Portland, Oregon, USA

On 5/8/2017 8:19 AM, penstemon wrote:

One thing about USDA hardiness zones, be they from 1936 or 2017: they
refer to the hardiness of woody plants. Nothing else. They have proven
very useful in the cultivation of other plants, but do not take into
account other important factors, notably the annual pattern of
precipitation, which is just as important as temperature to the
successful culture of bulbs in the open garden.

True. In Santa Fe, NM, a couple of weeks ago, I noticed large flowering plants of Cystisus scoparius everywhere. In Denver there are none, and yet winter lows are roughly the same. The only explanation I can think of is that Santa Fe receives at least twice the precipitation in autumn, which helps with the manufacture of cryoprotective sugars.

I always wonder why dwellers in the southwestern deserts of the US
(notably Phoenix!) don't use oncocyclus irises as bedding plants.

Different rainfall patterns; it rains in Phoenix in the summer. Not a lot, but more than none. Rain combined with heat might be fatal to the roots. The oncos grow their leaves in winter and receive twice as much rainfall in the wild, in winter, as Phoenix receives all year.
The sand in which desert species like Iris mariae grow is wet to a considerable depth in April.

Bob Nold
Denver, Colorado, USA
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