Ontario Weeds: Stinkweed
Excerpt from Publication 505, Ontario Weeds,
Order this publication
Table of Contents
- Other Names
- General Description
- Stems and Roots
- Flowers and Fruit
- Similar Species
- Related Links
Name: Stinkweed, Thlaspi arvense
Other Names: Fanweed, Field pennycress, Frenchweed, Pennycress, tabouret des champs, thlaspi des champs, monayère
Family: Mustard Family (Cruciferae)
General Description: Annual or winter annual, reproducing only by seed.
Stinkweed. A. Base of plant. B. Flowering and fruiting stem.
Stems & Roots: 5-60cm (2in.-2ft)
high, erect, branching in the upper part and sometimes also near
the base, hairless;
Leaves: The first several leaves usually in a basal rosette at the ground surface, these with stalks and smooth or slightly wavy margins; lower stem leaves with shallow, irregular teeth, rounded towards the tip and tapering towards the narrow stalk which has 2 little lobes or auricles which clasp the stem; middle and upper leaves shallowly or sometimes deeply toothed, without stalks but with a pair of lobes at the base which strongly clasp the stem.
Flowers & Fruit: Flowers white, very small (about 3mm, 1/8in. across) in rounded clusters at the ends of branches; seedpods very flat, rounded to oval, 8-12mm (1/3-½in.) wide and usually a bit longer; the central seed-containing portion slightly thickened but surrounded by a broad flat wing with a narrow deep notch at the tip, in the centre of which are the remains of the tiny style; seed-containing section divided into 2 compartments by a very narrow septum (membranous partition), each side containing 3 to 8 seeds; this white septum often remaining on the plant after the pod breaks apart to release the seeds; seeds reddish-brown to purplish or blackish, ovoid but somewhat flattened, 1.5-2mm (1/16-1/12in.) long with several rows of concentric ridges on each side. Flowers from early spring to late fall.
Habitat: Stinkweed occurs throughout Ontario in cultivated fields, waste places, roadsides and gardens.
Similar Species: It is distinguished from the pepper-grasses, which it closely resembles, by the complete absence of hair from stems and leaves, its unpleasant odour and its larger flat seedpods with a broad flat wing.
For more information:
Toll Free: 1-877-424-1300