HYB: Evergreen Leaves
- To:
- Subject: HYB: Evergreen Leaves
- From: J* a* C* W*
- Date: Sun, 24 Jan 1999 09:41:41 -0700
From: "Jeff and Carolyn Walters" <jcwalters@bridgernet.com>
> From: Linda Mann <lmann@icx.net>
> I agree, losing leaves for the winter and not getting started growing
> them again too early in the spring seems to be a good strategy for
> survival! But seeing how some of my 'new' historics have been reacting
> so well to the wretched weather while keeping their leavesgot me curious
> as to where that comes from.
Linda,
Observing how CONQUISTADOR (Mohr, '23) has been the only cultivar in a
newly planted bed of historic TBs that has maintained its foliage in a
green and undamaged state this far into the winter, I wonder if we might
not look to its tetraploid parent, I. mesopotamica, for an answer to your
question.
The type specimen of I. mesopotamica was collected near Mardin, which by
current political geography is located in southeast Turkey about 20 miles
north of the Syrian border. Mardin is situated at about 3000 ft elevation
nearly midway between the upper courses of the Tigris and Euphrates Rivers
(hence the "mesopotamica"). My world atlas indicates that the average
January temperatures in this area are between 30 and 40 degrees (the same
as for the Midatlantic region of the U.S. east coast). However, with its
elevation and semiarid climate I expect that the temperature variations
between daytime highs and nighttime lows would be greater in Mardin. In an
environment like this where occasional sub-freezing cold spells probably
punctuate longer periods of weather when active growth is possible during
the winter, might it not be adaptive for I. mesopotamica to develop
protective mechanisms to keep its foliage alive during the cold spells in
order to take advantage of the opportunities for active metabolism during
the milder stretches of winter weather? Perhaps in these conditions this
would be a better strategy than hunkering down for the duration like your
deciduous species. Since the occasional spells of sub-freezing weather are
inevitable, it would be necessary to have some form of insurance against
their effects - a plant in this kind of environment could not behave with
the naivete of a tomato - but would have to adopt a sort of "hold your fire
but keep your powder dry" policy.
Just theorizing.
Jeff Walters in northern Utah (USDA Zone 4/5, Sunset Zone 2)
jcwalters@bridgernet.com
Now "observing" irises through a 6" layer of freshly applied white mulch
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