Curly cup gumweed can invade pastures as well as roadsides.

The enemy

Curly cup gumweed (Grindelia squarrosa). This native plant is a light-green biennial or short-lived perennial with bright yellow flowers and belongs to the aster family (thistles and knapweeds). It gets its name from the outer coating of its seed head, which has curly bracts that are sticky or gummy.

At maturity the plant will reach a height of 2 feet and is prevalent in pastures as well as roadsides. This native plant has leaves that appear to be succulent or “fat.”

This plant has no forage value to livestock or wildlife, therefore it can continue to spread each year unless controlled or at least managed. Once established the plant does an excellent job competing against desirable vegetation for food and water. This is very bad as the plant is very drought-tolerant which allows it to invade much more effectively especially along roadways. The dead winter plants have a distinguished round seed-head with leafless stems.

The defense

Because this is not a noxious weed there is a limited amount of biological control research available. Due to its thick gummy coating over the entire plant, herbicide control is very difficult. Therefore you must think of ways to promote better herbicide absorption into the plant.

This can be done by utilization of products known as surfactants. These products not only help spread the spray droplets across the leaves, but they also help the herbicide penetrate through the cuticle (outer covering of leaf surface). Using these surfactants with good herbicides such as Escort XP, Opensight or Milestone will give you great results.

If you choose to dig the plant up make sure that you get down into the ground at least 5 inches.