Re: TB that do NOT make it thru hard winter

>You know what I would really like to see? A list of iris to AVIOD if 
>you live in a rather cold climate. It's nice to know those that will 
>live, but its also nice to know what ones to pass on.

I haven't been growing named irises long enough to make any judgements 
about specific cultivars, but I have made several cultural observations I 
believe are worth noting.  In my (very) northern garden, the primary 
factor determining winter survival of bearded irises is planting time.  
Irises planted before mid-August exhibit very high winter survival rates 
in their first year, irises planted mid-Aug through Sept have about a 
60/40 chance of winter survival, and irises planted after Sept are pretty 
much doomed.  

Even if newly transplanted irises do make it through their first winter 
(which most of mine appear to have done), the next major hurdle is 
avoiding spring rot.  In my garden, rot seems most clearly associated 
with soil texture and excessive moisture.  In areas of my clay that are 
heavily amended with sand and organic material, rot is not a major 
problem.  In areas of heavy clay that is not well-amended (even in raised 
beds), rot is rampant.

Summer rot and leaf spot are the next adversaries, but they seem to be 
big problems only where clumps have become crowded or are planted too 
closely together.  Having replanted everything last year at 2' spacings, 
I'm hoping to largely avoid these conditions for the next couple of years.

I have made one last interesting observation so far this spring.  I 
purchased over 100 new cvs last year from major growers on the West 
Coast.  I was concerned about the "pumped up", hot climate rhizs being 
able to survive up here, and I did allow them to dry out for a couple 
weeks before planting in July.  Even so, they were a good 3-4 times 
larger than any of my home-grown (peanut) rhizomes.  I figured my 
existing, fully acclimated rhizomes would have no problem with our winter 
weather, in spite of division and transplantation to new beds last 
summer.  Right now, however, with only about an inch of growth showing 
this spring, those hockey pucks from the West Coast are looking MUCH 
healthier and happier than my own northern rhizs.  Of course, I suppose 
it's possible that the rapid growth of those newcomers may leave them 
vulnerable to inevitable freezing nights to come, and perhaps my 
reluctant little peanuts will come through as the venerable tortoise did 
with the hare.  Time will tell.

Laurie
zone 3b, northern MN

 

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