Mustard Seed Weed

Mustard Seed Weed Erect annual, taprooted forb, 2 to 8 feet tall; stems usually glabrous and glaucous, sometimes with scattered stiff hairs toward the base; upper stems terminate in narrow The Weed Science Program’s goal at MSU is to provide science-based research and extension information on integrated weed management in field crops.

Mustard Seed Weed

Erect annual, taprooted forb, 2 to 8 feet tall; stems usually glabrous and glaucous, sometimes with scattered stiff hairs toward the base; upper stems terminate in narrow racemes of yellow flowers.

Leaves: The alternate leaves are 2 to 10 inches long, 1 to 6 inches wide, becoming smaller as they ascend the stems; lower leaves are pinnately lobed and obovate in outline, tapering to a long and rather stout petiole (not clasping), terminal lobe much larger than the lateral lobes, upper surface, often bristly with scattered hairs that are stiff, short, and white, lower surface usually glabrous, except for a few hairs along the central vein; upper leaves often lanceolate, broadly elliptic, or some other odd shape, 1 to 2 lobed or none.

Flowers: Flowers May to July; narrow racemes of yellow flowers, 6 to 24 inches long when fully mature; flower up to 5/16 inch across, consisting of 4 sepals and 4 yellow petals. The sepals are initially green, but become yellow while the flower blooms. The petals are well rounded toward their tips.

Fruit: Fruit is a silique, 5/8 inch long, tapering to a conical beak, appressed against the stalk of the raceme as it matures; petiole of silique (or flower) is about 5/16 inch long; seeds are dark brown or black.

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Habitat

Black mustard occurs in dry disturbed sites such as waste places, pastures, and along roadsides and railroad rights-of-way within elevations that generally range below 7,000 feet.

Propagation/Phenology

Reproduces by seed.

Comments

Native to Eurasia; black mustard seeds and foliage have a pungent taste. Black mustard grows profusely and produces allelopathic chemicals that prevent germination of native plants; in addition, the seeds contain an alkaloid and the sinapina the glucoside sinigrin. This species generally occurs as a weed in wildland areas of the Southwestern Region rather than as an invasive plant.

Weeds

Winter/summer annual. Emerges in late summer, early fall or spring. In Michigan, several populations of wild mustard act as a summer annual. Flowering peaks in June and July, but can continue until the first frost.

Emergence:
Emerges from soil depths of 1-inch or less.

Seed:

Production Range: Approximately 1,200 seeds per plant.

Dispersal Mechanisms: Seed pod dehiscence (splitting open).

Longevity: Low persistence – 50% of the seed bank is reduced in less than one year, and it takes seven years to reduce the seed bank 99%.

Dormancy: Initially dormant. Dormancy is broken by a combination of changes in temperature, light, and nitrate levels.

Competitiveness:

One of the more competitive weeds with small grains, soybean, and corn. Winter cereal yields were reduced 13 to 69%, when the biomass was comprised of 1 to 60% wild mustard. Soybean yields were reduced 46% with 4 plants per yard of row and corn yields were reduced 1.5- to 2-fold and 5- to 6-fold at low and high wild mustard densities, respectively.

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Preferred Soil/Field Conditions:

Grows on a wide range of soils.

Management:

Biological

Predation/grazing: Ground beetles (carabids) eat wild mustard seed lying on the soil surface.

Decay: No information.

Mechanical

Tillage: Seedlings are readily killed by tillage.

Rotary Hoeing: Hoe before weeds exceed 1/4-inch in height, once established wild mustard is difficult to control.

Flaming: Effective on small wild mustard.

Cultural

Crop rotation: Corn-soybean rotations will deplete wild mustard populations more rapidly than continuous wheat.

Planting date: Later planting will reduce wild mustard populations.

Chemical

Application timing and effectiveness: Several herbicides are effective for controlling wild mustard. Control is greater when herbicides are applied to smaller wild mustard plants. Please refer to E-434, “MSU Weed Control Guide for Field Crops,” for herbicide recommendations.

Additional Information

Wild mustard can serve as an alternate host of nematodes and many insect pests.