Going Soft

After cleaning up the damage to my plants from the hail storm on May 28th I didn’t cut back the damaged flower spikes to my German iris.  Not sure why I didn’t.  Probably because the flower stalks had injury but they didn’t seem to need immediate care.

However, making that deceisoin I probably did more damage to my iris bed then the hail did.  Bacterial soft rot in iris is caused by a bacteria called Erwinia carotovora and it is commonly found in the soil.  It is usually associated with the iris borer because it needs an entry point into the plant to start doing damage.  The hail provided that opportunity to allow the bacteria to do it’s job.  It took me two weeks to get around to checking out my iris and that was more than enough time for the soft rot to set in.

My first indication that something was wrong with my iris was yellowing of some of the leaves.  It was a wet May for us and I didn’t think much too it.  However, the smell of something rotting caught my eye (nose actually).  I started to examine the bed and noticed the damaged flower stalks were mushy and yellow.  I pulled out a few only to be knocked over with the smell of rot.

You cannot spray for soft rot – it is not a fungus.  There are not antibiotics on the market to give to your plant.  All that can be done is to cut back the plants, dig, and try to save the rhizomes that have not been infected.  When you have 37 iris clumps this puts a dampener in your weekend plans.

Each rhizome should be examined for signs of rot.  If so – toss them.  Only keep firm healthy rhizomes.  Disinfect the pruners as your move around the flower bed to prevent spreading the bacteria.  Once cleaned allow the rhizome to air dry for a few days then replant.  There is nothing that can be done to the soil.

Iris are a tough plant and they should make a full recover.  I just now know that we need to remove damaged plants from hail to prevent bacteria soft rot from setting in.

Flower spike rotting.
Soft rot in rhizome
Damaged flower spike



Scott Evans
Scott Evans is a horticulture assistant with Nebraska Extension in Douglas-Sarpy Counties. A certified arborist through International Society of Arboirculture and Nebraska Arborist Association. Scott is also Tree Risk Assessment Qualified through ISA. Scott co-leads the Master Gardener program in Douglas & Sarpy counties. Along with volunteer management he provides his expertise with disease and insect identification, lawn and landscape weed management, plant health, and I.P.M. practices. He also enjoys growing many houseplants ranging from African violets to cacti and succulents. Scott has two Bachelors of Science, one in Biology (emphasis in Botany, Ecology and Environmental Science) and second in Environmental Geology from Northwest Missouri State University. He earned his Master of Agriculture from the University of Nebraska-Lincoln.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.