Ontario Weeds: Wild mustard

Table of Contents

1. Name
2. Other Names
3. Family
4. General Description
   • Photos and Pictures
5. Stems and Roots
6. Leaves
7. Flowers and Fruit
8. Habitat
9. Similar Species
10. Related Links

Family: Mustard Family (Cruciferae)

General Description: Annual, reproducing only by seed.

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Photos and Pictures

Wild mustard (A - plants; B - flowers and seedpods).

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Stems & Roots: Stems erect, 20-90cm (8-36in.) high, branching in the upper part, harshly hairy near the base but weakly hairy or smooth upwards, greenish or sometimes purplish.

Leaves: Seedling with broad kidney-shaped cotyledons; stem leaves alternate (1 per node), somewhat hairy; lowermost leaves on young plants long-stalked and either without lobes or with shallow to deep lobes near the base of the blade; upper leaves stalkless and coarsely toothed but usually not lobed.

Flowers & Fruit: Flowers in small clusters which lengthen as the seedpods develop, bright lemon yellow, about 1.5cm (3/5in.) across with 4 small sepals, 4 larger petals arranged in the form of a cross (Family name "Cruciferae" means crucifix or cross), 4 long and 2 short stamens (total 6) and 1 slender pistil; flower stalks thin and short (3-5mm, 1/8-1/5in. long), becoming thicker but not longer as the seedpods develop, sometimes nearly as thick as the pod itself; seedpods (siliques) 3-5cm (1¼-2in.) long, sometimes bristly hairy but usually without hair, often with lengthwise ribs, erect and pressed to the stem or spreading out; each pod has a flattened terminal beak with 1 or rarely 2 seeds in its base and a main section containing several seeds which are released when the 2 sides or valves split apart from the bottom end and fall away entirely; seeds spherical, 1.5mm (1/16in.) in diameter, black or purplish. Flowering may begin as early as late May and continue throughout the summer.

Habitat: Wild mustard occurs throughout Ontario, being most frequent in cultivated fields and gardens, but occasionally appearing in fence lines, along roadsides and in waste areas.

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Similar Species: It is distinguished from similar mustards by its somewhat kidney-shaped cotyledons being broad with a deep, wide, rounded notch at the end, the hairy stem with lower leaves stalked and either lobed or unlobed but upper ones stalkless and merely toothed, its large flowers and its seedpod with a short thick stalk and a flat beak that is about 1/3 the total length of the pod and usually contains an additional seed or two; and from Yellow rocket by being annual with hairy stems, its lemon-yellow flowers usually not appearing before late May and its seedpods on short, thick stalks and having a prominent, flat beak containing 1 or 2 seeds.

Related Links

... on general Weed topics
... on weed identification, order OMAFRA Publication 505: Ontario Weeds
... on weed control, order OMAFRA Publication 75: Guide To Weed Control

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