Monday, November 13, 2017

Bloom Out in Bearded Irises

By Bonnie J. Nichols

In 2013 Texas had a wet and very cold winter.  We had more snow than we had seen in years.  The April 2014 bloom season was spectacular.  From the SDBs to TBs and beyond.  Winter in 2014 and 2015 had enough cold winter weather to give us good bloom. 

Then came last winter.  Actually, what winter?  In December when the Christmas Day temperature was 82 degrees and New Year’s Eve was 73 degrees, we knew the iris bloom season was in jeopardy.  And, it didn’t get better when on January 31st the high temperature of the day was 79 degrees.

When I saw various bearded irises blooming in December and January I asked friends if they thought the bloom was “rebloom” OR what would have been our April spring bloom.  We all had no idea.  In April, we knew the sparse bloom we had seen in December and January was “the spring bloom” because we kept waiting and kept waiting and we had no additional bloom.  Maybe 20% tall bearded irises bloomed and very limited (if any) of the medians bloomed.  The Louisiana and Spuria bloom was not damaged by the mild winter.

We skimped and scraped and came up with enough blooms for our iris shows and we shrugged off the fact that we could not control Mother Nature.  We saw more than normal increases on some of the plants because they did not use their energy to bloom.  On other plants we noticed something that we had not had much experience with – “lightbulb” bloomed-out rhizomes.  Lightbulbs are rhizomes with no increases and the roots wither away.  Now I can spot the “lightbulbs” before digging.  The rhizome increases in size and twists slightly as if it is pushed out of the ground.  This could be the result of the roots drying out.  Some of the “lightbulbs” bloom.  The bloom stalk comes up in the middle of the fan and dies back quickly.  The rhizome eventually dries up and dies also.

When I see a lightbulb rhizome sending up a stalk, I have unsuccessfully tried to make crosses on the blooms.  I was hoping to force a pod and force the plant to increase. 

While my experiments and observations are interesting…………I hope we have a colder winter in 2017 and eventually get back to good iris bloom and the “lightbulbs” are a thing of the past.  However, as I write this article we are 2 ½ weeks from Thanksgiving and our Dallas temperature high today was 91 degrees.  Global warming? – I’m not sure; however, I’m beginning to believe it is.


  1. Interesting information. Strong root growth is what produces good spring bloom here. Makes me wonder is the prolonged heat might have created a false dormancy due to the heat and the plants did not root deeply. Late planting here coupled with moisture shortage generally makes for a lousy bloom season here.

  2. Great article, Thanks for your nice data, the content is quiet attention-grabbing. i'll be expecting your next post.


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