Mustard Seed Weed

Wild mustard control can be a challenge because this is a tough weed that tends to grow and create dense patches that out-compete other plants. Wild mustard is a pain, but it is a bigger problem for farmers than for home gardeners. Learn how to control the weed in this article. 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 Weed control, management, ecology, and minutia

Wild Mustard Weeds – Tips For Wild Mustard Control In Gardens

Wild mustard control can be a challenge because this is a tough weed that tends to grow and create dense patches that out-compete other plants. Wild mustard is a pain, but it is a bigger problem for farmers than for home gardeners. You can use both physical and chemical strategies to manage or eliminate wild mustard in your yard or garden.

About Wild Mustard Weeds

Wild mustard (Sinapis arvensis) is an aggressive weed native to Europe and Asia, but one which was brought to North America and has now taken root. It is an annual that grows to about three to five feet (1 to 1.5 meters) and produces yellow flowers. You will often see these plants growing densely by the roadside and in abandoned areas. They are mostly problematic in cultivated fields, but wild mustard plants can take over your garden too.

Controlling Wild Mustard Plants

Because it’s so tough, getting rid of wild mustard can be a real project. If you do not want to use chemicals in your garden, the only way to eliminate this weed is to pull it out. The best time to pull mustard weeds is when they are young. This is because they will be easier to pull out, roots and all, but also because removing them before they produce seeds will help limit future growth.

If you have too many to pull, you can mow down wild mustard before seed production, during the bud to bloom stages. This will limit seed production.

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Unfortunately, there are no other cultural or biological control methods for wild mustard. Burning does not help, nor does allowing animals to forage. The seeds of wild mustard can actually be toxic to livestock.

How to Kill Wild Mustard with Herbicides

Herbicides can also be effective in controlling wild mustard. There are several different types of herbicides that will work against wild mustard, but there are some that the weeds have grown resistant to and that will no longer work.

There are different varieties of wild mustard, so first determine which type you have and then ask your local nursery or university agricultural department to help you select the right chemical.

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.

Mustard Seed Weed

As we start the winter season today, many locals and tourist to our area look forward to the end of winter when the Napa Valley comes alive with the beauty of yellow mustard flower that has been celebrated for many years in the ‘Napa Valley Mustard Festival.’ No one can argue the aesthetic beauty of a hillside vineyard covered in the yellow flower of mustard. Working as the Farm Advisor who oversees vineyard floor management in the Napa Valley, I am at times troubled by the sight. Is there an invasive weed that has ‘taken over’ the vineyards? If it is a covercrop, is it good cover crop? And the question I get most often from grower and city folk alike, ‘What kind of mustard is that?’ Consulting the ‘Weeds of California and Other Western States’ it appears that the Napa Valley has at least five “mustards”; Short-pod mustard (Hirschfeldia incana L.) that can become a short-lived perennial, and four species that are all at some point referred to as ‘Wild Mustard’: Wild mustard (Sinapis arvensis L.); Rapeseed mustard (Brassica napus L.) Black mustard (Brassica nigra L. Koch); and Birdsrape mustard (Brassica rapa L.). How do you tell the difference? To really tell the difference you need to look closely at the flowers and the orientation of the mature fruit in relation to the stem.

Are these mustards weeds or covercrop? The answer, as with most weeds, depends on your perspective. Mustard as a group may be one of the best examples of both. In many parts of the country mustards are a serious weed problem in vegetable and cereal production. However, they also have several properties that make them a good covercrop: large tap root that can break up hard soils, usually germinate and grow quickly, providing erosion control and weed suppression, large biomass that can contribute to the organic matter of the soil, and contain chemical constituents that can provide limited nematode and weed suppression. These ‘mustards’ usually germinate in the fall when the rains start, then flower, and set seed in late winter, in time to mow for frost protection.

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So, if wild mustards can act as a covercrop, why, according to many long-time Napa Valley locals, do we have much less mustard than before? There are some properties that make mustard a less than ideal covercrop. Deeply buried seeds of some species can survive for up to 50 years. Early flowering reduces growth and weed competition. Wild mustards break down very quickly and add little organic matter and almost no nitrogen to the soil. A wide variety of more suitable plants are available as covercrops, such as domesticated mustards(White mustard or Daikon radish) that have shown promise of more positive properties without as many of the negative. Other covercrops are better suited to the specific needs of the vineyard. Cereal grains, such as oats or barley are often used where vines are too vigorous or in vineyards that tend to hold moisture in the spring. Many growers utilize a ‘no-till’ system comprised of low-growing annual or perennial grasses, and where organic matter and nitrogen are needed a cereal/legume mix of barley or oats with winter pea or fava (bell) bean is very popular.

The amount of mustard in the valley may have diminished, but there will continue to be an abundance of this attractive yellow flower to enjoy for years to come…