Oncocyclus iris, was 1936 usda zones

Shmuel Silinsky gardenbetter@gmail.com
Thu, 11 May 2017 01:35:41 PDT
Leo Martin wrote concerning failed oncocylus iris
The people in the iris society concluded they got too much winter rain
here. We average 8" / 200mm rain per annum, 60% during the summer monsoon
July-September.

I cannot beleive that the 8"/200mm of yearly rain in Phoenix is too much
winter rain. Of course, the species vary, but even desert species like Iris
mariae do fine in the Jerusalem Botanical Garden which gets avg 550 mm of
winter rain and dry summer.  My oncos are in the ground on a slope with
unmodified terra rosa soil - a clay soil from weathered limestone. They do
fine - and I give the area an occaisional soak in the summer which may
mimic your 120 mm of summer monsoons..

My personal feeling is that too dry and too loose a mix may be the problem.
A key component of the summer dry climate, at least here, is dew. I feel
dew is underrated as a factor in maintaining soil moisture in dry times,
especially when a plant has a bulb or rhizome close to the surface. I
lightly water the area weekly, even in the deep summer. I use xerophytic
perennials and subshrubs in the bed to moniter the water situation - if
they show stress, I water. I rely on the winter rains and the occaisional
soakings to leach out salts left from light waterings of our tap water.

All the best,

Shmuel Silinsky
Jerusalem Israel
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