Impatiens glandulifera

Photo credit: Barbara Tokarska-Guzik, University of Silesia, Bugwood.org

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Description

Himalayan balsam is a member of the Touch-me-not family (Balsaminaceae).
Ornamental jewelweed is a showy herbaceous annual, capable of growing to over 6 feet in height. The pink to purple flowers are generally borne in clusters on long slender stalks known as peduncles and bloom in the lower Hudson Valley region from mid to late summer. The plant’s translucent, watery, often hollow stems are hexagonally angled, and occasionally red tinged. (6)

Leaves
Leaves are 2-6” long, opposite to whorled (on the upper portion of the stem), lance-shaped, and strongly serrate with pointed, acuminate tips.

Flowers
This species pink to purple flowers are irregular in shape, approximately 1 inch in length, with a short, curved nectar spur at the flower’s base.

Introduction History

Introduced to Europe from its native Himalayan range in the mid-1800s, Ornamental jewelweed has traveled around the globe due to its popularity as a garden annual. It is now extant in 31 countries, and at least 12 states. (2)

Ecology and Habitat

Ornamental jewelweed can colonize wet meadows, floodplain forests, wetlands, swamps, and other sites with high moisture in sunny to partly sunny conditions. However, this species is not yet known within the Lower Hudson PRISM region. It is found in numerous sites throughout the neighboring Catskills throughout Sullivan County. (3)

Reproduction and Phenology

Ornamental jewelweed produces copious amounts of seed which is released explosively from a ripened capsule when disturbed. Seed is commonly transported by water too, as ripe seeds are buoyant. Although this species does not purportedly have a persistent seed bank, seeds can and are frequently transported in soil, particularly in the horticultural trade. The abundant nectar production of flowering ornamental jewelweed has been observed to reduce seed set in other plants. (4) Vectors include water, soil and horticultural trade.

Impacts of this species

Ornamental jewelweed produces copious amounts of seed (up to 800 per plant), making it an aggressive, fast spreading self-seeder, particularly along river edges and in other high moisture environments. Although the species is frost intolerant, dense stands of this quick growing annual can outcompete other vegetation. The gradual replacement of more deeply rooted perennial vegetation with ornamental jewelweed can lead to increased erosion along stream banks and the alteration of natural riparian hydrology. (3)

Management Methods

Biological Control
Only a handful of insects are known to feed on ornamental jewelweed outside its native range. As of now, no biocontrol option exists.

Manual or Mechanical Control
Pulling / Digging Up As an annual with shallow roots pulling is very easy and very effective. Populations should be monitored for at least 3-4 years to ensure the seed bank is exhausted. (3)

Mowing: Mowing, weed whacking, or cutting is effective so long as the plant is cut below the lowest node to inhibit regeneration. Populations should be monitored for at least 3-4 years to ensure the seed bank is exhausted. (3)

Girdling: Not applicable

Prescribed Fire: Not applicable

Torching: The high moisture content of ornamental jewelweed stems makes torching plants a lesser effective means of management.

Prescribed Grazing: Grazing has been shown to reduce biomass of ornamental jewelweed, primarily due to the trampling of seedlings. (3)

Soil Tilling: Tilling is not a recommended method of control as ornamental jewelweed often colonizes fragile, wet soils vulnerable to erosion.

Mulching: Mulching is a successful method of control for small, newly emerged seedlings. (5)

Solarization: Solarization is a successful option if the population levels are small and the site is not on vulnerable soils where near-term regeneration of vegetation is necessary.

Hot Foam Spray: No information available

Chemical Control
The pesticide application rates and usage herein are recommendations based on research and interviews with land managers. When considering the use of pesticides, it is your responsibility to fully understand the laws, regulations and best practices required to apply pesticides in a responsible manner. At times, the pest you seek to treat may not be on a pesticide label, requiring a 2ee exemption from NYSDEC. Always thoroughly read the label of any pesticide and consult the NYSDEC or a licensed pesticide applicator with questions.

Foliar Spray: A springtime foliar spray of 2-3% glyphosate pre-flowering is effective against this species. Herbicides containing triclopyr, 2,4-D, or metsulfuron are all effective and do not affect grass species. As ornamental jewelweed inhabits wet environments, only products safe for use close to water should be utilized for this species. (5)

Cut Stump: Not applicable

Basal Bark: Not applicable

Hack-And-Squirt

Stem Injection: Not applicable

Pre-Emergent Spray: Not applicable

Summary of Best Managment Practices

General management overview and recommendation
As an annual with a short-lived seed bank, ornamental jewelweed can be managed by hand pulling over the course of several years of consistent management. Consideration must be given to the wet, often vulnerable sites ornamental jewelweed colonizes, such as frequently disturbed stream banks. Cutting, by mechanical or manual means, if possible, causes less soil disturbance than pulling and allows quicker regeneration of soil-stabilizing vegetation than mulching, or solarization.

Post treatment monitoring
Controlled populations should be revisited for at least three years to ensure complete exhaustion of the short-lived seed bank.

Additional Information

REFERENCES

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