How to Get Rid of Comfrey

Comfrey (Symphytum officinale) is a flowering herb, but is also classified as a weed. It spreads in clumps through an extensive root system, according to Washington State University Extension, and is hard to get rid of once it is established. Rototilling comfrey only makes the problem worse, because every fragment of root left in the ground will produce a new plant. If you want to get rid of comfrey without chemicals, it can be done with repeated attacks.

Spade

Black plastic sheeting or cardboard

Mulch

Boiling water

Glyphosate herbicide spray (optional)

Pick the day after a rain for removing comfrey from the landscape. Cultivate around the base of each plant with a spade to loosen dirt and roots. Pull upward gently and steadily from the base of the plant. Feel it start to let go, pause, then pull again, making sure you get the entire root. Repeat this process with every comfrey plant you want to remove.

Cover the weeded area with pieces of cardboard or black plastic sheeting. Either one will keep air and light from reaching the soil and nourishing root fragments. Black plastic, in particular, will trap heat and "cook" any seeds waiting to germinate in the soil.

Spread a 2-inch layer of mulch over the cardboard or black plastic sheeting to keep it from blowing away or shifting, and to make your landscape less unsightly.

Remove the mulch, cardboard or sheeting after one year. If comfrey returns, pour boiling water over the root crown of the young plants to kill them.

If your comfrey problem persists, you may want to use a targeted, light spray of glyphosate herbicide on comfrey foliage to kill it.

Avoid a wide nozzle spray when using glyphosate. It will kill any foliage it touches, including mosses, grasses and other plants in your garden.