Description: This adventive or introduced plant is a
summer or winter annual about 1-4' tall, branching occasionally in the upper
half. Initially, there is a rosette of basal leaves, but during warm weather
this plant has a tendency to bolt and develops flowering stems. These stems are
round and hairless. The alternate leaves are up to 12" long and 4" across. The
typical leaf is pinnatifid, tapering gradually to a stout petiole and becoming
broader toward the large terminal lobe. There is a stout central vein along its
length. A few of the upper leaves may be unlobed. These leaves are bluish green
(usually), glabrous, and glaucous, while their margins are undulate or dentate.
The upper stems terminate in narrow racemes of yellow flowers. Each flower is
about ½" across, consisting of 4 yellow petals, 4 yellowish green
sepals, a short green pistil with a knobby stigma, and several stamens with
yellow anthers. The rounded petals are slightly notched at their tips, and have
faint veins running across their length. The pedicel of each flower is about
1/3" long or longer. The blooming period usually occurs from late spring to
mid-summer, but some plants bloom during the late summer or early fall.
Individual plants remain in bloom for about a month. Each flower is replaced by
a hairless silique (i.e., a seedpod) that is cylindrical and held more or less
erect. A mature silique is about ¾–1¼" long, and has a
conspicuous beak at its tip. There are 2 faint lines running along its length.
The small round seeds are arranged in a single row within each silique. The
root system consists of a taproot. This plant spreads by reseeding
itself.
Cultivation: This plant
typically grows in full sun under mesic to dry conditions. It is not fussy
about the characteristics of the soil, and can often be found in clay-loam or
gravelly sites. However, fertile soil will produce larger plants. Disease
rarely bothers this plant in the wild, although various insects often chomp
holes in the foliage.
Range &
Habitat: Indian Mustard occurs occasionally in scattered counties of
Illinois, especially in the NE, east-central, west-central, and SW areas of the
state (see
Distribution
Map). It is originally from Asia. Habitats include areas along railroads
and roadsides, cropland and abandoned fields, vacant lots, and
miscellaneous
waste areas. In Illinois, this species occurs in highly disturbed areas, and
does not invade high quality natural areas to any significant
degree.
Faunal Associations: The
nectar and pollen of mustard flowers attract flower flies and small bees.
Occasionally, Pieris rapae (Cabbage White) and other white butterflies
suck nectar from the flowers. The caterpillars of Pieris rapae (Cabbage
White) feed on the foliage, although they appear to be less common on the wild
form of Indian Mustard than many cultivated plants in the Mustard family. In
the Midwest, the seeds are rarely consumed by birds or small rodents, with the
possible exception of the Mourning Dove. Small plants may be eaten by rabbits,
while larger plants are eaten by livestock. In large quantities, the foliage
may be toxic to livestock because of the mustard oil and other sulfur
compounds.
Photographic Location: A
junk pile along a railroad in Champaign, Illinois. By moving the mouse cursor
over the upper photograph, a close-up of the siliques (seedpods) will be
revealed.
Comments: This species is
the source of many cultivated forms of Indian and Chinese Mustard. It resembles
Broccoli or Collards in appearance, but these cultivated plants are apparently
different forms of Brassica olearacea (Wild Cabbage). Indian Mustard
differs from Wild Cabbage by the absence of leaves that clasp the central stem.
It differs from other Brassica spp. (Mustards) in the wild by the lack
of hairs on the foliage, seedpods, or stems. While some cultivated forms of
Indian Mustard have leaves that are incredibly hot and spicy, the wild form of
this plant has leaves with a mild flavor (in my experience). They are edible
and can be used as a potherb.