Hoary cress, aka
whitetop, is a perennial forb originating from Eurasia. It is a member
of the mustard family (which includes broccoli) and was probably introduced
to North America in alfalfa seed. Hoary cress reproduces by seed and
creeping roots. The root system spreads horizontally and vertically
with frequent shoots arising from the root stock. The stems can grow
between 10 to 18 inches tall.
Leaves are alternate and clasp the stem. The margins are wavy and shallowly
toothed. Flowers are white, numerous, and occur in flattop clusters
which give the plant its name. Seed pods are heart-shaped and contain
two oval red-brown seeds about 1/2inch long.
Hoary cress is one of the earliest perennial weeds to emerge in the
spring. Flowering occurs between late April through May. It is an aggressive
weed that forms dense colonies that make it difficult to control. Hoary
cress can be found in pastures, small grain fields, roadsides, meadows,
and waste places. Vigorous growth is likely to occur on irrigated sites
and areas with alkaline soils. It can be found anywhere from 3,500 to
8,500 feet in elevation.