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Re: Iris growing north of Parry Sound

  • Subject: Re: [iris-talk] Iris growing north of Parry Sound
  • From: laurief <laurief@paulbunyan.net>
  • Date: Thu, 27 Sep 01 22:53:04 -0600

>Soil light sandy with leaves and compost started to be mixed in .. 

I grow irises in northern Minnesota where our temps sometimes drop 
significantly below -25, so perhaps I can offer my own insights based on 
only 3-4 yrs iris growing experience (in other words, don't take my 
observations as gospel - I'm still a fairly novice iris gardener).

My first thought is that you may need to feed your irises more frequently 
than you currently are.  Fertilizers tend to leach out of sandy soil far 
more quickly than they do out of my heavy clay.  Have your soil analyzed, 
and add any nutrients shown to be insufficient for maximum iris 

>This summer I only had one bloom between all 8 plants.  
>Obviously I am doing something very wrong. 

Not necessarily, but maybe.  Irises need 6 or more hours of direct 
sunlight a day for optimun performance.  They don't like to be crowded or 
to compete with neighboring plants for sunlight, water, and soil 
nutrients.  Irises will not bloom until their rhizomes are mature, so if 
you planted relatively small, immature rhizomes, they will need some 
extra time to grow to blooming size. If you planted your irises after 
mid-August last year, they may not have had time to root in adequately 
before winter.  In my experience, that can severely impact an iris's 
ability to grow the following year.  In my cold climate, I do everything 
possible to see that all irises are in the ground no later than the end 
of July.  

It's also important to realize that in a short northern growing season, 
the entire growth and bloom cycle of irises slows down.  The same 
cultivar that may bloom and increase madly in its first year in the hot 
South may go bloomless and grow only a single increase its first year in 
a cold zone.  We northern growers have to be more patient with our irises.

>I did NOT put anything 
>on top of the iris for winter protection and this may be why no 
>blooms in summer 2001.

I don't believe that would have negatively impacted bloom.  It could 
possibly have impacted survival of first year plants if they were planted 
too late or if there was inadequate snow cover to protect the plants from 
repeated freeze/thaw action.

>Should I plant the rhizome deeper?

No.  If you plant the rz too deeply, the plant will refuse to flower.  
It's also far too late in the season to be disturbing iris roots this far 

>won't it freeze right through?

Yes, it will.  It's not the freezing that might harm it.  It's repeated 
freeze/thaw cycles that can injure rhizomes.

>   Or should I just cover the plant with something?

In my experience, winter mulch on bearded irises is a good news-bad news 
proposition.  The good news is that mulch will help prevent those 
potentially injurious freeze/thaw situations.  The bad news is that 
bearded rhizomes can easily rot under compacted mulch, esp if it is not 
removed at the proper time in early spring.  My first year growing 
bearded irises, I planted many of them waaaay too late in the season and 
decided to mulch them to give them a better chance of winter survival. I 
covered them with spruce boughs on top of which I spread a layer of 
straw.  The results were disastrous.  About 70% of the rhizomes rotted 
and died the following spring.  I attributed that primarily to the late 
planting, but the mulch may have played a factor as well.  I now make 
sure I plant early in the season, and I don't mulch.  If we get a 
severely cold winter with no or little snow cover, I suppose I may end up 
losing many of my irises.  Last winter was more than cold enough, but we 
did have adequate snow.  I had very few losses among my approx. 250 

I hope something I have written here will prove useful to you.

Happy growing,


zone 3b northern MN - clay soil

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