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Hoary Cress (Whitetop) (Cardaria draba) has occupied a spot on the Utah Noxious Weed List since its first drafting. Whitetop or Hoary Cress is a perennial mustard that grows up to 2 feet tall. The leaves are blue-green in color. Only the lower leaves are stalked; the others are stalkless and clasp the stem with 2 earlike lobes. The short, flowering branches bear many very small flowers (right photo), each with 4 petals about l/8 inch long, giving the plant a flattop appearance. The white flowers occur only at the terminal ends of the stem. Seeds are formed in a pod. Hoary cress, introduced from Europe and Western Asia, forms large patches in cultivated fields, gardens, pastures, along roadsides and waterways and is very competitive with native vegetation.

Pictured below is a typical infestation of Hoary Cress along a drainage ditch near Highway 89 in North Weber County.


Historical journals from Northern Utah farms record very early efforts to control Whitetop. Land managers used salt on patches of the weed to try and suppress it. This invader is a survivor, however, and constant attention must be given in order to successfully eradicate an infestation of Whitetop. It doesn't spread extremely fast, but its growth habit results in a very dense root mass. Whitetop infestations should be constantly monitored. Maintain ranges and pastures. Promote healthy grass growth through proper irrigation and fertilization. Do not overgraze. We are not aware of any biological control methods for Whitetop. Mechanical and chemical control measures can be effective if timely.