Rodney and All
OK, you invited comment. Here goes. Actually I
prefer to call "winter hardiness" by the broader term "winter survival". There
are so many factors involved in over wintering of species and derived cultivars
in a given geographic position, that an index or "winter hardiness
description" can hardly predict future performance. Zones,
longitude/latitude, temperature, and many more devices have been
tried. They often are good general comparative guides, and I am NOT
suggesting we abandon them, but most of us can cite their past
failures.
Winter survival is the result of a
broad complex of factors including geographic position, macro
environmental factors at that position, micro-climate factors,
cultural effects, disease and pathogen loads, nutrient balance-supply, and
factors we can't even detect. Then genetics and specific cultivars
matter. All which merge to determine final
winter survival at that place in that
year. Time then
becomes the huge variable because the preceeding pieces
of the survival pie are dynamically changing over time.
Further, there are multitudes of
"interactions" between these individual components that mask understanding.
Interactions alone impact winter
survival ! A good example is the well documented three legged stool of
genetics/disease/environment interactive cumulative effects which can
modify plant performance and determine, in part, if that plant is
a perennial survivor at that place and time. Thus, we have plants
that are perennial; surviving winter at some places and times, not
all.
The natural world is so wonderfully challenging and
dynamic. There is THE excitement of gardening, to me. Try to
grow it; see if it survives. Share those experiences.
irisman646
----- Original Message -----
From:
r*@yahoo.com
Sent: Saturday, January 16, 2010 9:34
PM
Subject: Re: [iris-species] Hardiness of
Species Irises
Hi All,
Thanks for all the comments so far. I've not really had
time digest it, but please continue if you have comments. All are
welcome!
Thanks!
Rodney
From: Diane Whitehead <voltaire@islandnet.com>
To: iris-species@yahoogroups.com
Sent: Sat, January 16, 2010 7:50:12
PM
Subject: Re:
[iris-species] Hardiness of Species Irises
Debbie's information about Alaska is interesting.
One other variable
is timing. Usually our temperatures gradually get
colder and plants
fortify themselves for the winter. Occasionally we
will get an arctic
blast while everything is still in full growth. I
can remember a fall when
the trees hadn't turned colour yet - their
leaves were still green, and
got frozen onto the branches so we had
brown-leaved trees all
winter.
In England, and perhaps other European countries too, gardeners
worry
about spring frosts when plants have begun growing again.
I
agree with those who said we should note the plants that grow well
in our
normal conditions.
It is reassuring to have a reliable source of
information about
hardiness. The usual U.S. zone information is not very
helpful to me
here on the Pacific coast.
One set of books that I
have found consistently reliable is by Roger
Phillips and Martyn Rix,
published in the U.K. Their numbers may not
be at all helpful to those of
you with a continental climate, but
perhaps they might. You may find it
helpful to look at their
recommendations for plants you are very familiar
with, to see if you
can trust them with advice about plants that are new
to you.
For my conditions, if they say a plant is OK at -15 C (5 F),
the
plant will be completely hardy, at -10 C (14 F), it will live most
years, but get killed in a bad winter which happens perhaps every ten
years or so.
I see I should not have been growing confusa outside.
I didn't check
first.
Here are a few samples of iris from their
book Perennials Volume 1:
confusa: -5 C 23 F
clarkei: -15 C 5
F
delavayi: -15 C
wilsonii: -15 C
lazica: -15 C, leaves killed at -10
C
unguicularis: -15 C
cristata: -20 C -4 F
setosa: -25 C -13
F
versicolor: -25 C
Diane Whitehead
Victoria, British Columbia,
Canada
maritime zone 8, cool Mediterranean climate
mild rainy winters,
mild dry summers
