Hairy whitetop fruits
Mary Ellen Harte, Bugwood.org
Hairy whitetop is native to southwest Asia. It was likely introduced into the U.S. in contaminated alfalfa seed.
Keywords: Brassicaceae, perennial, herb, forb, extensive roots, Cardaria pubescens; Common names: globe-podded hoary cress, ball cress, white-top, hoary cress
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Hairy whitetop distribution
Hairy whitetop is a perennial herb or forb growing to ½ m tall with erect hairy stems. Hairy leaves are alternate, gray-green, up to 8 cm long, and obovate, lanceolate, or oblong to elliptic with irregularly toothed to entire margins. Numerous fragrant 4-petaled white flowers blooming from April to September have hairy sepals and often appear in flat-topped inflorescences. Hairy whitetop produces an average of 300 seed pods per plant. Seeds are dispersed by water, vehicles, farm machinery, and contaminated hay and crop seeds. Although seed production is somewhat important, the aggressive nature and stubborn persistence of hairy whitetop is due to an extensive system of vertical and lateral roots. New shoots arise from buds on creeping laterals and may form many independent clonal plants if severed. Hairy whitetop grows under a wide range of environmental conditions and is found in irrigated croplands, roadsides, rangelands, wildland areas, and riparian-upland ecotones. Invasion potential is greater under heavily grazed conditions or other disturbances. Infestations may exclude native species, reduce biodiversity, and decrease rangeland productivity and forage quality.