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Re: Northern/cold weather hardiness

  • Subject: Re: Northern/cold weather hardiness
  • From: irischapman@aim.com
  • Date: Thu, 02 Apr 2009 10:41:14 -0400

This certainly helps.

I keep records of min/max temperatures of air and soil temperatures
(5-6"below surface of soil) I just checked some records. The hotest
summer we had for some time was 2007. Even though we had 5 days in a
row with max temp over 35C, we only had three days all summer when min
temp was over 18C.

The windbreak helps. Are there any geographic features nearby that
might work on balancing temperature?

I would encourage you to get a thermometer to record temperature. there
are a number of inexpensive min/max digital thermometers. The records
need to be recoded daily. There are more expensive ones that can
record data for a month and then download to a computer. You may indeed
have a micro climate wher you are. Roses can surcome to damage to
wood from temperatures or a combination of drying out plus cold. Iris
plants are tucked in nicely for winter, and if they have white mulch,
will even be more protected.

This past year I noted bud set and bloom on Queen Dorathy following 4
days of min temp over 15C. It was several weeks after before we got 7
days of min above 15C. This was followed shortly by more rebloom,
including Immortality. Immortality was primed to bloom (had a mature
leaf count) but needed the 6+ days to set bud. I also noted the sharp
increase in growth of increases co-related with the bud initiation.

Thus keeping this data will help with20the project.

Chuck Chapman

Re: Northern/cold weather hardiness

Posted by: "SandraB"


Wed Apr 1, 2009 11:10 am (PDT)

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

the house ranging from about 3 feet from the house to about 20-30 feet

so other than wind protection I don't think they are getting any extra

from the house. It doesn't seem to make much difference where the

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

that. I do have a Zone 4 rose -Madame Hardy) in my west bed that I

never mulched over the winter and it has lasted over five winters and

consistently. Other zone 4 plants I have tried I have lost over the


generally have just iris beds rather than a mix of irises and other

which probably is different than a lot of p

When I first started with TB's the main reason I lost irises was due to

for e.g.. pulling the dead leaves off in early spring when it was still

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

of the irises I get will have five or more good sized increases by the

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

of my soil/rot but I have tried covering

the rhizome with a two inch mound of sand when I get the rhizomes in

August. I plant toe down because that is the end that usually comes up

the soil when you get freezing/thawing - the heel more

anchored down by the roots. I did that when I got a order from

in mid August one year and other than one extremely small rhizomes of

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

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

TB's in a SD
B 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

one year when they do decide to bloom they I get the entire clump

As to temperature, depending on what your definition of summer is - if

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

where the temperatures was not less than 21C or 70F for 6 nights in a

( I could be mistaken on this but that is what I

remember). Basically, I guess you are saying we need a six day period

nights in the 60's F and that usually happens later in August although

the variability of our weather lately it could happen in July

as well.

Hope that helps answer your question.


SE Manitoba

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