Other than I tend to neglect them more than most people would, I am not sure
what exactly I am doing differently. I don't have any iris beds right
against the house. I have TB's beds on the east, south, and west sides of
the house ranging from about 3 feet from the house to about 20-30 feet away-
so other than wind protection I don't think they are getting any extra heat
from the house. It doesn't seem to make much difference where the irises
are planted in the beds because I have tried moving some irises like
Clarence to different beds. El says I have a hot spot - I don't know about
that. I do have a Zone 4 rose -Madame Hardy) in my west bed that I have
never mulched over the winter and it has lasted over five winters and blooms
consistently. Other zone 4 plants I have tried I have lost over the winter.
generally have just iris beds rather than a mix of irises and other plants
which probably is different than a lot of people.
When I first started with TB's the main reason I lost irises was due to rot,
for e.g.. pulling the dead leaves off in early spring when it was still wet.
Since I don't do a lot of weeding/cleaning anymore I don't
lose irises to rot. I do tend to like buying from the west coast so a lot
of the irises I get will have five or more good sized increases by the end
of year of planting, this may help since the increases will survive when the
main rhizome sometimes does not (usually when planted in August again will I
encounter the main rhizome dying). I don't plant the rhizome deeply because
of my soil/rot but I have tried covering
the rhizome with a two inch mound of sand when I get the rhizomes in mid
August. I plant toe down because that is the end that usually comes up from
the soil when you get freezing/thawing - the heel more
anchored down by the roots. I did that when I got a order from Pennsylvania
in mid August one year and other than one extremely small rhizomes of Renown
I didn't lose more than one and that one lasted
the winter but was extremely crowded by the others so I am not really sure
it is dead but since it never bloomed it may as well be.
For irises that don't bloom consistently - I think I have one of B Blyth's
TB's in a SDB bed (farther than 30 feet from the house - more like 50 feet -
I ran out of room that year) I almost always get increase instead and then
one year when they do decide to bloom they I get the entire clump blooming.
As to temperature, depending on what your definition of summer is - if you
are using July and August, then rarely would we not have a summer where
sometime in there there was a period of over
15 C or 59 F for six nights, conversely again rarely would we have a period
where the temperatures was not less than 21C or 70F for 6 nights in a row
( I could be mistaken on this but that is what I
remember). Basically, I guess you are saying we need a six day period of
nights in the 60's F and that usually happens later in August although with
the variability of our weather lately it could happen in July
Hope that helps answer your question.
Sandra, can you identify what is different in your garden/culture that
would result in such good survival, that is not seen in other in your
climate. Planting on the south side of a house or wall is one thing
that can make a difference in a cold climate. Many plants that don't
survive in colder area, is not because they are killed by cold, but
because temperatures for triggering bloom and increases are not met in
the growing season. Thus they slowly fade out. The temperatures for
bud set and this seems to be related to the triggering of increases,
would seem to be between 15-21C. Thus if summer minimums don't exceed
15C for 6 nights, no bud set and limited increase. Same if temperatures
don't go below 21C for 6 nights in a row. At least this is what my
current experiments/research suggests. In both of these circumstances
we would see gradual decline over several years and eventual death of
plant. Of course, this is very much a cultivar variable, so some will
make do with cooler or warmer trigger temperatures.
For this last reaon, I'm encouaring trial participants to record
min/max temperatureson a daily basis during growing season
A lot of various rambling.
Northern/cold weather hardiness (Chuck)
Posted by: "SandraB"
Tue Mar 31, 2009 9:22 am (PDT)
Chuck that list of plants provided in the AIS bulletin was I believe
taken from people who grow those irises in their cold climate gardens.
I personally don't believe in providing people
a list of 'cold hardy' irises and because of that I didn't provide a
list to Kate of irises that are cold hardy. I actually didn't agree
with much of that article myself based on my fifteen years experience
growing TB's iris in my garden. Like I said previously I have very
little problems with TB irises surviving the winter if they are planted
early enough. In addition, once they survive that first winter then
they rarely have a survival problem after
.. If you are talking about
irises that continue to grow and increase in later years then I don't
believe you are necessarily talking about cold hardiness, but rather
aren't vigorous and that is not necessarily specific to cold climates.
There are certain irises that may just do better with certain soils, a
certain climate during the growing season (e.g. hot summers, dry vs
wet, etc.) and certain management practises.
For instance, Romantic Evening, that iris, is the worse
grower/increaser I have. It has bloomed the majority of years I have
had it (I think over four winters now and I moved it once in that
time), but it barely increases and it always blooms on short stalks
with misshappen flowers. Now I could say that iris isn't cold hardy,
but is it actually a good grower anywhere ?
As for blooming consistently, I have learned from Linda in US Zone 7,
that it is the fluctations in temperature in the spring that often kill
the bloom on the iris and I believe Donald has also mentioned the same
thing - so are we going to say irises that don't bloom consistently
aren't cold hardy when they do the same sort of thing in Texas ? I
actually think for your climate Chuck, Linda would be able to help you
than for someone in a real cold climate for genetics that are less s
Also, I would like to make a comment about medians, especially dwarf
bearded irises. In the past five years I have purchased a lot of SDB
irises (because they take up less space) and I have probably lost just
as many of them in portion to the numbers I have purchased as I do
TB's. So does th
at mean the SDB are now getting less cold hardy (there
are some of them that are sure a lot less vigorous) ?
I recall talking to you about Rhonda Fleming - that iris did well for
me. I believe it would meet your five year trial definition, but your
experience with that iris was that it was tender - so I think other
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