Out in the Weeds With Ecological Services - Hoary Cress (A.K.A. Whitetop) Lepidium draba

Hoary cress is a highly competitive perennial weed that quickly forms a dense monoculture and displaces vegetation. It is considered one of the worst weeds for agriculture because it severely reduces pasture and crop production. It is a Colorado State List B noxious weed species and its containment is the goal. Montrose County works diligently to suppress hoary cress along roadsides.

Hoary Cress Characteristics

• Leaves are blue-green and lance-shaped

• Begins growth early in the spring from a rosette

• Lower leaves are stalked

• Upper leaves are alternate, clasping, and oval or oblong

• Flowers are white with four petals

• Inflorescence is flat-topped

Negative Impacts

• Out-competes native plant communities

• Grazing animals and wildlife have less sources for food because they do not eat hoary cress

• Quickly takes over pasture and cropland leading to reduced production

Management Strategies

• Pulling and tilling of hoary cress is not recommended. Deep root systems allow plants to regrow if entire root system is not removed

• Mowing hoary cress repeatedly can stress the plant’s root system. Repeated mowing in the summer followed by fall herbicide applications has shown to be very effective

• Chemical control is effective while weeds are actively growing. For a list of suggested herbicide active ingredients for hoary cress control, please refer to the 2025 CSU Herbicide Recommendations.

Always read, understand, and follow the label when making herbicide applications.

For more information regarding hoary cress and its management, visit the CSU Hoary Cress Fact Sheet.