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Weed Identification

field mustard

Family

Brassicaceae

Scientific Name

Brassica rapa

Other Common Names:

bird's rape
birdsrape mustard
wild mustard
wild rutabaga
wild turnip

Habit

Plants germinate or sprout in fall, are green during the winter, and produce flowers and seed in the spring and early summer. Plants usually die back with summer heat. The stems are erect, 3 ft tall, branched, hairy, and usually bluish-green in color.

Leaves

Leaves are light to medium green, hairy or bristly, stalked, and are 12 to 20 in long. Like most mustards, leaves tend to feel rough due to the stiff hairs on the leaf surface. Leaves are often ravaged by insects and often appear with holes or eaten portions missing.

Identifying Characteristics

The flowers have four petals that form a cross.

Flower Seed Head

Flowers bright yellow; petals 6-10 mm long; those in maturity close together and commonly overtop the unopened buds; outer 2 stamens are much shorter than inner stamens.

Seed Fruit

Fruit is 1 1/2 to 2 1/2 in long with long tapering beak. Seeds are blackish or reddish-brown and 1.5-2 mm in diameter.

Where Found

Found along roadsides and waste areas. A common weed of agricultural fields

Growth Habit

upright and nonwoody

Thorns or Spines

not present

Approximate Flower Diameter

dime

Dominant Flower Color

yellow

Flower Symmetry

radial symmetery

Leaf Hairs

Varies: 
no hairs
has hairs

Leaf Shape

lance

Leaf Arrangement

alternate

Leaf Margin

Varies: 
serrated
wavy

Leaf Structure

simple

Leaf Stalk

none

Stem Hairs

no hairs

Stem Cross Section

round or oval

Milky Sap

not present

Root Structure

taproot

Life Cycle

biennial

Ochrea

not present

Plant Type

Herb