Small-flowered Jewelweed
Impatiens parviflora
Washington State Classification
Class A — Eradication Required Statewide
This is a new noxious weed for 2018.
Quick Reference
Identification
Growth Habit
Small-flowered jewelweed is an annual that is glabrous or with sparse stalked glands on upper plant parts. Plant height can vary greatly depending on growing conditions. Flowers are small, pale yellow and have a short, straight spur.
Leaves
Leaves are alternately arranged and have short petioles. Leaf blades are elliptic to ovate-elliptic, 1.6 to 7.9 inches long by 0.8 to 3.5 inches wide, the uppermost leaves typically the largest. Leaf base is wedge-shaped, tapering down the petiole and the leaf apex is acuminate (gradually tapering to a sharp point) or shortly acute. Leaf margins serrate or crenate-serrate, teeth directed forward, often with stalked glands near the base. Petioles may also have stalked glands.
Flowers
Small-flowered jewelweed inflorescences grow in the upper leaf axils and are typically comprised of 3 to 12
Fruit & Seeds
Small-flowered jewelweed produces capsules that are glabrous, linear-oblong, club-shaped or
Impact
This is a new noxious weed for 2018. Small-flowered jewelweed is an annual that can invade and adapt to a variety of habitats. Plants can grow well under low light conditions as well as tolerate lower moisture conditions. Plants are able to dominate the herb layer of invaded forests, forming large, monospecific stands, displacing native species. Small-flowered jewelweed may have some allelopathic effects, results have been found in lab studies but it is unknown how these results relate to natural conditions.
Ecology & Spread
Habitat
Plants typically grow in shaded places with dry to moist soils. Habitats include: forests, forest clearings, forest edges or paths, riverbanks, lake shores, disturbed and cultivated sites and occasionally in open sites. Click here to see a county-level distribution of small-flowered jewelweed in Washington..
Spread Mechanisms
Reproduction
Small flowered jewelweed reproduces by seed. Capsules can explosively eject their seeds many feet when touched. Seed also float in water and are helped further by being carried on animals and birds, footwear, vehicle tires, and with timber.
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