Re: RE: Cult-Botrytis
I have heard time and again in this area, I can't keep Cooley's, they die on
me. I have not tried them for this reason. On the other hand the same
people will buy the Cooley's rhizomes, after they have been planted
somewhere else for a year and have good luck with them?
I do dry my incoming Iris for at least a week and then I do wash them for
about 10 min in 1 part bleach and 10 pats water. I do that with the ones I
sell as well. So old timers in the area insist it is the only way to keep
the Iris Borer under control.
Char Holte, New Berlin, WI (Near Milwaukee)
----- Original Message -----
From: "Chuck Chapman" <email@example.com>
Sent: Tuesday, April 13, 2004 12:16 PM
Subject: [iris] RE: Cult-Botrytis
> I really enjoy your posts and knowledge. I would like to ask about a
> conclusion you may have reached about the size and water content of
> Oregon iris. Do you really think it is the water content that is
> significant? Wouldn't you think that it may be the adaptability, vigor
> and resistance of the cultivar itself rather than the area of origin.
> Naturally then, wouldn't a rhizome bred and grown and adapted for
> generations in the West have a different tolerance of soil and water PH,
> micronutrients etc etc than those in the Eastern part of the country? I
> have had iris from the East that have done very well and then others that
> have struggled too so I wonder. I had tentatively decided that it had
> more to do with the suitability of the particular line of breeding than
> the size of the rhizome. Some just adapt and are stronger growers than
> others and it is especially apparent when the location of growth is so
> different from the location of transplanting. Thoughts?
> Have you ordered iris from California and how did they do compared with
> the Oregon iris? I've found that if I order from a reputable nursery
> with a good guarantee, some may fail to thrive or die but they will be
> replaced. This botrytis thing is really a personal fascination for
> me...but then.I also wish they could find a cure for the common cold!
> Hopefully hybridizers will keep working on the resistance and vigor of
> new intros for the garden.
> Interesting post. Thanks for taking the time to share with the list. I
> like to hear your thoughts.
> Char Randall
> Melba, Idaho USDA zone 6
> Feel free to print my posts re Botrytis.
> I have heard various theories re amount of water content but havn't found
any conclusive supportive information. Some people claim that if they let
them dry out first that there is less of a problem. Enough people claim this
to add some plausibility to this theory. Personally I have my doubts. That
is doubts as to why it seems to work. Besides drying out the rhizome it also
puts the rhizome into deep dormancy so less growth before frost comes. Of
note is that this drying process seems to have more beneficial of an effect
in warmer climates.
> I have received large rhizomes from California and from other hybridizers
(other then Cooley's and Schreiners) in Oregon and have not had the problem
with these rhizomes. Also have had my own home grown large rhizomes that
don't have the same problem with Botrytis. If it was just size and water
content these other rhizomes hould also have the problem and they don't have
> It does not seem to be the cultivar as once they get through the first
year they are fine. Replacement plants often survive well (with or without
treatment) and no problems seen with daughter cultivars.
> Someone told me that they thought (actually report having seen) ground
being fertilized with chicken manure and they speculated that that may be
contributing to the problem. Perhaps so but not from the extra nitogen.
Extra nitrogen causes a problem here but the problem is soft rot, not
Botrytis. We have to be sure to use a fertilizer lower on nitrogen in order
to reduce soft rot problems.
> I have not figured out exactly why Botytisis is a problem with certain
suppliers or how it is spread. As the soaking procedure seems to help I
have speculated that it is a contamination of the surface of the rhizome.
> A shipping procedure of the large suppliers is to dig large quantities of
each cultivar and store them in laarge bins from which they are selected for
shipping. They are also transported in large bins from field to the packing
station. What if over time these bins have become a breeding ground for
Botrytis and subsequently infect what is stored in them? This is one
possiblity. Of course this is testable. You only need to sterilise these
storage and transportation bins before the start of the shipping season.
Then see if it has any effect on amount of problem.
> It may be a combination effect. Large rhizomes planted traditionally, have
teir backs exposed to the air. In colder climates you typically will get
some warm sunny days (in late fall and in mid-winter and late winter) while
ground is still frozen. This means back of rhizomes are warm and base is
cold. The warm parats expand and the bottoms dont. This will result in many
microfractures in surface of rhizome, particularly at soil line. These
microfractures leave openings for entrance of disease entities such as
botrytis and soft rot. These diseases can progress at low temeratures when
plant is not actively growing. An actively growing plant can sometimes out
grow these diseses. Particulaly so with daughter plants.
> Drying out rhizomes can thus provide some protection as the plants then
have less moisture and thus less expansion/contraction problems and thus
less microfractures and thus less entry points for disease. This could work
especially well in warmer climates as plant will still have time to come out
of deep dormancy and still put roots down for winter survival.
> In Canada the plants usually take several weeks (one case of 8 weeks last
year) to get here so often have already gone into deep dormancy. Here this
is a problem as we don't have a lot of time for plant to settle in for
winter and a delay before stating growth can be quite detremental to winter
survival. Winter protection with straw etc. does help. Winter protection
doesn't keep plnts warm, quite the opposite. It keeps plants cold. Thus you
get much less otf the warming of the backs of the plants and thus less
microfractures for disease entrance.
> I have been planting rhizomes deeper then recomended over the past several
years and found good results. Better winter survival, less winter heaving
and no adverse effects on blooming or reproduction. I have been planting
with about 1/2" of soil over rhizomes. Starting to go even deeper as it
works so well. I do have well drained soil so this may be a factor.
Increasingly I have found other well known growers have also been breaking
the shallow planting rule (even in California and Oregon) and found the same
> Before soaking I remove all dead or dried out foliage. I'm currently
wondering if a brief soak in 50% chlorine bleach would work as well as
> Schreiners offer a non conditional guarantee on their plants and replace
with absolutely no quibbles. Cooleys have stopped ofering their extended
guarantee to Canadian customers. While these are the only places where I
have experienced this problem I have heard of other people experiencing
problem with other western growers.
> Chuck Chapman, Guelph, Ontario, Canada. Zone 4/5
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