A Daily Dirt reader recently wrote in to find out what she could do about cattails were planted in a low wet area, but that are spreading into the lawn. There are a couple of options: Biological, mechanical or physical, and chemical. Unfortunately none of them are very good, but for different reasons.
Cattails reproduce by two methods, rhizomes and seeds; one is above ground and the other is below ground, but both are fairly aggressive, which makes cattails become a nuisance species very quickly. Most experts agree that there is no true biological method of control. I have heard of people using mallard ducks or muskrats, but I wouldn’t recommend importing them to your property if they don’t already live there, as they can become nuisances themselves. The second option is mechanical or physical removal. While potentially labor intensive, this is the preferred choice for those of us not wanting to use chemical intervention.
This method works best for “new invasions”. Once cattails are established it becomes difficult. Weeding young cattails must be done aggressively and regularly when they reach six inches above the water line or when the shoots appear on the lawn. The entire plant must be pulled up including the root (rhizome) system. Simply cutting off the tops will not kill the plants. Frequent mowing might also help. Chemical intervention involves our friend glyphosate (of Roundup fame), the active ingredient in Rodeo or another herbicide called diquat, trade name Reward.
For more details on eradication check out this fact sheet about common cattails from the Wisconsin DNR.