Arnica Weed Control

Identification

• Arnica faces hard competition from a number of perennial weeds such as white clover. If not controlled in time, white clover can strangle and destroy arnica plants. According to the Crop & Food Research Newsletter, there are no registered products for weed control in arnica.

Description

• White clover belongs to the legume family and has fast-spreading, fibrous roots. The weed has a creeping growth habit and the stems root at the nodes. The dark green, 4/5-inch-long compound foliage has crescent-shaped marks, and the ball-shaped clusters of pink or white flowers bloom between May and September.

Management

• Since herbicides are not registered for clover control in arnica, cultural management practices provide best control. These include hand pulling or hoeing larger weeds. Apply a 4-inch-thick layer of organic mulch such as compost or woodchips to retard germination of clover seeds. If seeds have germinated, apply a thicker mulch layer to suppress seedlings. The use of woven, black landscape fabric also helps to keep the weeds out.