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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.
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 benifical results.

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 benylate.

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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