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Re: CULT: non-blooming iris

  • Subject: Re: [iris-talk] CULT: non-blooming iris
  • From: Anne McManus <joeannemchig@yahoo.com>
  • Date: Mon, 27 May 2002 14:41:04 -0700 (PDT)

 Thanks so much, that was very helpful.
  laurief <laurief@paulbunyan.net> wrote: >they are not in an overly sunny spot, in fact 
>if anything its shady, I have lots of pine trees in the yard.  They have 
>not been cut back and the leaves themselves look very robust.  They were 
>in big clumps last year and I thought that was the reason for no flowers 
>so I have spread them out, but again no flowers.  I haven't tried the 
>fertilizer but will do that.  Do you suggest any particular kind?

Hi Anne,

I wrote a FAQ for the Iris Forum about potential causes of non-bloom in 
bearded irises based on things I learned from the folks here on 
iris-talk.  I'll paste it below so you can see if the suggestions might 
help you get your irises blooming.  One thing not specifically mentioned 
in the FAQ is that some people growing irises in very sandy soil have 
found it advantageous to feed considerably higher levels of nitrogen in 
their fertilizers because it leaches out of their soil so quickly.  High 
nitrogen can cause serious problems for bearded irises in loam or clay 
soil, but it might benefit them in your sand.  Just a thought.

Here's the FAQ:

Here are a few reasons why bearded irises may not bloom: 

       Not adequately established 
              Some iris cultivars need a year or more to fully establish 
in their new locations
              before blooming. If you relocate them frequently, they may 
never become well
              enough established to bloom. Plant irises far enough apart 
to allow for several
              years' growth before requiring division. 
       Inadequate sun 
              Bearded irises need at least 6 hrs of direct sun a day to 
bloom well. 
       Nutrient deficiencies 
              Consider having a soil test run to make sure your soil 
provides all necessary
              plant nutrients in appropriate amounts and fertilize 
according to the
              recommendations returned with the soil analysis. Soil that 
has been growing
              irises for many years without amendments or fertilization 
is probably
              nutritionally depleted. Avoid high-nitrogen fertilizers. If 
bearded irises are fed
              high-nitrogen fertilizers, they may grow lush foliage with 
little or no bloom. 
       Inappropriate watering 
              Bearded irises might not bloom well if they experience 
periods of extended
              drought, though the plants themselves are quite 
drought-tolerant. Conversely,
              bearded irises that are overwatered are often susceptible 
to bacterial soft rot
              and fungal leaf spot infections. If you provide 
supplemental water, water
              deeply no more than once a week. Soaker hoses are 
preferable to overhead
              watering to avoid spreading leaf diseases from plant to 
       Planted too deeply 
              Bearded iris rhizomes should be planted so the tops of the 
rhizomes are at or
              slightly below the soil surface. If planted too deeply, 
bearded irises will grow
              leaves but may not flower. Be careful, also, not to allow 
mulch to cover the
              rhizomes. Make sure any mulch is pushed away from the 
              Overcrowded clumps often quit blooming until they are 
divided, OR irises
              closely planted with other plants may not bloom well (or at 
all) if they are
              struggling to compete for sunlight, water, and soil 
              There are certain weeds and grasses that are so aggressive 
they can inhibit the
              performance or even survival of plants they invade (Canada 
thistle being one
              of them). Keep the weeds and grasses away from your irises. 
       Ill health 
              Irises that are diseased or under insect attack may not be 
able to bloom until
              the problem is eliminated. 
       Late freezes 
              If a late freeze occurs when flower stalk development has 
already started, the
              stalk may abort. 
       Immature rhizome 
              Rhizomes will not bloom until they are mature. If you have 
planted smaller
              rzs, you probably need only wait for them to grow a bit 
before they'll bloom. 
       Irregular bloomer 
              All irises are not created equal. While some irises may 
bloom very regularly
              in your garden once established, others may never do any 
better than
              blooming once every several years ... or perhaps never 
blooming at all. The
              same cultivars that bloom beautifully and reliably for a 
neighbor down the
              road or a friend across the country may do nothing more 
than sulk in your
              own garden. The only way to discover which irises will 
perform best for you
              is to keep trying different cultivars, growing them 
properly, and replacing
              those that don't meet expectations within 2-3 years after 

Hope that helps,


zone 3b northern MN - clay soil

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