Sun, 25 Nov 2012 19:05:36 PST
Thanks Peter!

The coldest we have experienced here is -32F (-35.5C ?).  It used to always
get at least -10F (-23C).   However, things have been warming for several
years now and the coldest it has gotten was two winters ago with -22F
(-28C).  Then one year it only got down to 14F.  Some years it dips to -4 or
-8 for just a few hours which is just long enough to do damage.  We also no
longer have the generous snow pack that we used to.  I generally plant for
the worst case scenario as it is too expensive to lose things every few
years.  We also have WIND.  The cold, dry air combined with extreme winds
really dries things out.  In the summer we can get dry winds that will take
away the moisture in the upper inches of soil in a matter of minutes after I
just finished watering.  With all of these stressors my iris, which until
this year, were all very old, did not multiply as most seem to expect them
to do.  No clumps.  

So far I don't think I have had bacterial rot, though I just may not have
known what it looked like.  Thanks for all your sharing.  I will save this


-----Original Message-----
From: []
On Behalf Of Peter Taggart
Sent: Sunday, November 25, 2012 11:18 AM
To: Pacific Bulb Society
Subject: Re: [pbs] Iris

Hello Colleen,
If you do not lift the dahlias from the ground, the mulch should be a very
good idea for them, and for most lillies too.
However bearded Iris tend to get a bacterial rot (and greenfly which
transmit virus), if warm and /or humid. cold and airy is better for them.
Many bearded Iris species will in fact burrow their rhizomes under the
surface of the ground, especially most of the Oncocyclus and Regelia
species, as well as Iris reichenbachii, variagata, attica, pumila..... Most
historic Iris have a lot of Iris Pallida in them, which is less fussy, as
well as I variagata, aphylla and pumila.
If these are planted in humus rich soils they tend to rot, though I have
found I variagata in particular more resistant.
In my experience, many of the bearded Iris, and in particular the ones which
do not grow with their rhizomes on the surface, are very reluctant to put
down roots if the rhizomes are not buried, as you have observed. - I
normally mulch them with grit or gravel.
I would expect that in your less humid climate that many of these Iris would
indeed do better planted well below the surface, but a gravel mulch rather
than an organic one would be more appropriate.

The UK has a very variable climate. My normal minimum winter temperature
here is about minus 10 c, however I have had two recent winters with several
weeks of minus 15c or colder at night. Occasionally winters here are almost
frost free.
Peter (UK)

On Sun, Nov 25, 2012 at 6:35 PM, Colleen <> wrote:

> Thanks Sean,
> While your area and mine are about the same temperature zone, I think 
> you are probably more humid.  I think what is going to happen is that 
> I won't be able to remember just where all the iris are planted so 
> some will get uncovered and some will remain covered and the results 
> will be a highly uncontrolled experiment!  Hopefully it won't be 
> disastrous.

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