Iris – damage, small holes in rhizomes


Hi. Something has dug up a mass of irises in my yard. I’m not sure if it was an animal or if this is a sign of insect damage. There are small holes in some of the rhizomes. The clump was long overdue to be thinned.

I’m wondering if is likely raccoon (or skunk) perhaps digging for grubs? I’ve seen no caterpillars or grubs but have not inspected closely, yet.


Thank you for contacting the Toronto Master Gardeners concerning your Irises.

It is certainly frustrating when wild animals dig up plants in the garden.  We have numerous gardeners writting us with this very question. The following information is from one of our earlier post.

The culprits could be skunks, raccoons, voles, rabbits, ground squirrels, or even birds.  The irises can be transplanted most successfully between July and September when summer conditions are dry.  Protect newly planted bulbs with1-inch mesh poultry wire. Dig a trench slightly deeper than the desired depth of planting and fit the poultry wire in the bottom. Add dirt and plant the bulbs. Place another strip of poultry wire over the plantings so that the bulbs are completely encased, and finish covering them with a small amount of dirt.  Once the irises are established you might consider putting up barriers such as tomato cages or other supports around them.  As well, your local nursery might suggest organic products that will deter small animals while leaving plants and beneficial insects unharmed. If you feel your existing iris clumps are getting too large, you may also choose to divide your irises at this time, and replant them into smaller clumps – this will revitalize them, and help to prevent disease. ” Here is a Penn State Extension website that describes how to go about this: Dividing Irises

You mention that you see small holes in some of your iris rhizomes. If these tiny holes are on the underside of the rhizome, this is where old roots have died and is perfectly normal. It could be that the holes are caused by the Iris borer. The rhizomes might look fine until you push on the rhizome and find that they are a mushy mess. Iris borers chew pin prick holes into the leaves of the Iris plant in early April, May and continue to tunnel down to the rhizome. Evidence of the presence of the Iris borer include tan streaked or water-soaked leaves. Did you see any evidence of this? According to the University of Illinois Time to Divide Iris the best way to control Iris borer is to remove and destroy old plant leaves and plant debris after a hard frost. The University of Minnesota has an excellent link, Iris Borer on the timely detection of Iris borer. It should be noted that they recommend the use of pesticides which are restricted for use in Canada.

Good Luck with your Iris.

July 31, 2021