Richard from Dalton Gardens, Id writes
Digging iris does not rid my pond or area of it. It is now a weed and I tried roundup but it wasn't effective.
Tenacity is not labeled to control undesirable ornamental plants, although it may harm them if sprayed accidentally. You will need to remove physically all the parts of the iris - including the rhizomes in the soil – in order to prevent these plants from regrowing the following year. You can use a glyphosate product such as RoundUp QuikPro to kill the above ground plants, but you will need to remove the rhizomes after spraying. This article has easy-to-follow directions on this treatment, which is best done in the fall.
Answer last updated on: 10/30/2019