Hoary cress plants, also called whitetop, are deep rooted mustard perennials growing up to 0.5m tall with numerous erect or ascending stems. They are commonly found on alkaline and disturbed soils and are highly competitive with other plant species.

They were accidentally introduced to North America from western Asia and eastern Europe as seed contaminant, and due to problematic behavior in many agricultural settings, are now considered noxious in many US states. Hoary cress is also considered invasive in some natural areas.

The plants reproduce clonally from creeping horizontal roots and less often from seed. The two species and two subspecies have different chromosome numbers and herbicide resistance. All are self-incompatible.