An early Monday morning, and the fall weather is here in Ohio. It is very chilly and I will be clean up the rock garden here in Bellbrook. It is time to put it to bed for the winter and I need to make sure it is well weeded. I guess the deer will have already had morning breakfast when I get there. They keep the larger sedum well trimmed. ( Read that as “eaten down to the ground.” It’s going to be a chilly clean-up! But I like to do it before the sun gets high.
Today I will be offering you some advice on taking care of your iris in the fall. I have an “Oh, aren’t they pretty” reaction, to “I am tired of that ratty foliage” after they have their spring bloom.
I think it is best to remove all this foliage in the fall. Those blades or leaves are where the adult moth laid her eggs and those eggs overwinter in the foliage. Cutting off all that foliage to approx two inches in the fall may help to reduce the infestation of this common enemy of the iris. It is called Macronoctua onusta. You may see a caterpillar which is about two inches long, but the moth itself is usually active at night. It is a large moth with dark brown wings in front, and a yellowish brown wings to the rear and its wing span is about two inches.
Clean up the iris bed in fall, October here in zone 6, cutting the iris blades down to about two inches.
Gather and destroy all of this debris either by burning or wrap in a garbage bag and discard. Get rid of all the surrounding debris from other plants too. A clean bed is best so that there is nothing for any eggs to remain and overwinter until spring.
It is in the fall when the adult moths emerge from the soil, mate, and lay their eggs. And you guessed it, they lay their eggs in the iris leaves. Those crinkled, and brown dead leaves are the perfect place for them to overwinter. So it is all of this vegetation that needs to be removed so there is no place for those iris borer’s eggs to remain, waiting to hatch in the spring and climb into the leaves or blades and bore down through that blade on its munching trip down to the rhizome.
Oh, by the way, if you have the stomach for it, it is said those caterpillars working their way down the leaves can be found and pulled out and used as fish bait. Ewww! For me, I will pass on squishing them out….<shudder>
So that is my advice for keeping your iris nice throughout the years. And this is my experience and what I have been taught. Try it in your garden and you may find it helps.
I do feel that cleaning up the garden in the fall is the best thing you can do to help your garden. And it makes it so much more pleasant in spring to NOT have to start cleaning up all that mess.
And remember, don’t mulch til the ground is frozen! See my reasons here.
Have a nice week! Hope your beautiful fall colors last a lot longer. Let’s not get snow too soon! It is way too early, but I know we’ve had snow many times on Halloween!