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Re: mulch

Nancy Coffey wrote:
> Here's a question for all you northerners. When the ground was frozen and
> it snowed a couple of weeks ago, I put straw mulch on all my irises, since
> I had divided them this year. Now the temperature is up in the 40's and it
> has been quite wet. Should I pull the mulch back until the ground freezes
> again to avoid rot, or will they be OK?
> I'm sorry that I forgot to use my 'garden' signature. I'm in Ontario, just
> east of Toronto, zone 5b.

Chris(a northerner)replies:
The advice that has been given regarding mulch from the UK is not really
applicable in whole to your climatic situation in southern Ontario,
Canada. The "winter" conditions here are totally different.

First, we are talking WINTER mulch here.(verses decorative or moisture
retentive,etc., etc.) 
The following is a repeat of what I have written previously about WINTER
mulching in our climate:

Another thing that you might consider is the application of a winter
protective mulch over your irises. (probably will be helpful to all your
other plants as well) 
This mulch would consist of getting a bale or two of straw from a nearby
farm and covering the garden beds with the straw a couple of inches
thick so it forms a nice thick mat. This is not to keep the plants warm
but keep them cold! The mulch controls the particular problem that we
have here in southern Ontario of extreme cold with little or no snow
cover mixed with intermittent warm periods during the winter. The
alternate freezing and thawing is what can cause damage to the plants.
The mulch helps keep the ground temperature more or less constant during
these sometimes radical temperature fluctuations.(40F one day, 0F the
next day) In areas of deep snow cover through the winter, the snow does
the same job naturally. By keeping the ground cold the iris are less
likely to become "tricked" into starting their growth cycle too soon
which can be extremely bad for them. This can occur when we have a warm
period for a 10 days or more(say 45-50F) in Jan or Feb followed by a
severe cold snap to 0F)(this causes damage which leads to rot later on
in the spring)

When to apply the mulch? Depends on the first onset of winter cold...
but usually I wait until the ground gets frozen hard for the first
time... usually the end of November or start of December here in
Ontario. Take it off about the end of March.(again somewhat depending on
the weather conditions) 
(Our ground here freezes solid to a depth of 2 to 3 feet during the
winter, during the warm spells the top 1-2 inches may thaw during the
day with the sun on it but then refreeze solid at night)

In conclusion, for our particular winter climate, DO NOT take the WINTER
mulch off in the intermittent warm periods through the winter as you
will be defeating the purposes of placing the mulch in the first place
as well as creating unnecessary work for yourself.

Christopher Hollinshead
Mississauga, Ontario  Canada  zone6b
AIS Region 16
Director, Canadian Iris Society
Newsletter Editor, Canadian Iris Society
e-mail: cris@netcom.ca
www: http://www.netcom.ca/~cris/CIS.html

  • References:
    • Re: mulch
      • From: "Nancy Coffey" <ncoffey@inforamp.net>

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