White Cockle is a County Scourge

white cockle

By Harry Brook

One of the main weeds we have in this county that seems to be spreading is white cockle. At this time of year, you see a lot of flowers showing up along fence lines, especially in the boundary between the field crop and the edge of the road. The field edge is a difficult zone as some over-spraying by field operators can leave patches of bare soil, the perfect place for invasive weeds to start.

White cockle as an invasive weed is either a biennial or short-lived perennial. It is a little unusual as male and female flowers form on separate plants. It often starts as a rosette of lance-shaped leaves, about 1 to 4 inches long. After forming a rosette, the stalks emerge and have leaves opposite, two per node. Both the stalks and the leaves are covered in fine hairs but the plant is not sticky, like night-flowering catch-fly.

This particular weed is a prolific seed producer, having up to 24,000 seeds per plant. That is why it is important to try and prevent the plant from going to seed. It spreads only by seed and seed size is around one millimeter. When flowering, it is easily seen, particularly in the mornings, but flowers can close when temperatures increase. It is especially a problem in hay land and headlands. As it is difficult to separate from alfalfa and clover seed, it can be a contaminant in hay seed. Using certified hay seed with a weed certificate can help prevent it from getting established on your land.

There are several ways to try and control the plants. If cultivated, you have to go deep enough to sheer the crown from the root and deposit it on the surface to dry out. Root pieces can generate complete plants if moisture is good. Herbicides can work but the hairs on the leaves make it difficult to get much herbicide into the plant. There are several herbicides and herbicide mixes that have some effect on it but they usually contain metsulfuron methyl. It is not usually a problem in annually cropped land but can be a major problem in hay. Importing hay from areas where white cockle is present is another way for this weed to enter your land.

If you mow the flower heads, you can prevent seed production but the root can regrow new shoots and seed production later in the summer is a possibility. If you have a thick, healthy hay or grass stand, it can effectively shade out the white cockle and prevent it from establishing. However, once established, using crop competition is not effective at preventing plant growth and seed production. In other words, it is much easier to keep it out than to try and eradicate it. And finally, small infestations can be picked out but the entire root must be removed to be effective. It is not poisonous to livestock but it is also not particularly palatable.

White cockle is a problem in many parts of the black soil zone. It thrives along fence lines and in hay fields. It takes a concerted effort to eliminate it and unfortunately, there is plenty of it in Flagstaff County. Let us know of any infestations so we can address the problem on County land and help get it under control.

Harry Brook is Flagstaff County’s Agricultural Fieldman. He can be reached via email at: or by phone at: 780-384-4138.