Another member of the mustard family, Whitetop is a long-lived perennial that spreads by creeping roots and a prolific seed base. It grows up to two feet in height. It is often confused with Hoary Alyssum. While Hoary Alyssum generally produces a long stem with small elongated leaves and two to three branches each with a single flower, Whitetop stems have broader, clasping leaves below a branch of stems culminating in a flat umbrella of small, four petal white flowers. A large infestation of plants will create a solid white appearance. Controls include mowing prior to and during flowering, grazing by sheep, cattle and goats, and some herbicides.  Herbicides such as Escort XP or Opensight containing metsulfuron or chlorosulfuron are effective when combined with a non-ionic surfactant. 2,4,D will kill plant tops but not the root systems. A heavy seed base will require multiple treatments to eradicate. Each plan can produce up to 3000 seeds annually.