Policeman's helmet

Herbaceous annual with hollow stems and swollen nodes, growing up to eight to 10 feet tall. Pink-purple flowers and explosive seed pods similar to other jewelweeds or "touch-me-nots."

Other names for this plant include:

• Common names: Ornamental jewelweed, Himalayan balsam, jewelhead, Royale ornamental, Indian balsam
• Scientific names: Impatiens roylei

Classification in Wisconsin: Prohibited

Ecological Threat

• Invades rich forests, riparian areas, open grasslands, meadows, lake edges and disturbed areas such as ditches and field edges.
• It can produce up to 800 seeds per plant, which have long viability and high germination rates. Seeds can even germinate underwater.
• Forms dense colonies that outcompete native herbaceous plants and reduce overall forest regeneration.
• Seeds are easily spread by the ejection of mature pods as well as by human activity.
• Widespread invasive alien plant throughout Europe.

Identification

Leaves & stems: Fleshy, smooth, hollow stems with a reddish color. Stems are multi-branching with distinct swollen nodes. Leaves are large, simple and toothed with a pointed tip. Leaves are arranged opposite or are often whorled in groups of three.

Flowers: Flowers resemble an English policeman's helmet, giving this plant its common name. Flowers are spurred, five parted and pink to white to purple in color. Flowers arise from the leaf axils.

Fruits & seeds: Seeds eject from mature seedpods when touched. Seeds are viable in the soil for 12-18 months.

Roots: Fairly shallow, fleshy roots.

Similar species: Policeman's helmet could be mistaken for other members of the genus Impatiens. This species pinkish-purple flowers, swollen nodes and serrated leaves distinguish it from two native Wisconsin jewelweed species (Impatiens capensis, Impatiens pallida).

Control

Mechanical

• The best way to reduce its spread is by inhibiting seed production.
• Cutting, mowing or weed-whipping are very effective controls and reduce disturbance compared to hand pulling. Cut as close to the ground as possible. Repeated treatments may be needed, as plants can regenerate from cut stems and small regrowths can flower and produce seeds. Cutting/mowing during the flowering stage will reduce this.
• Bag and dispose of all plant debris that is in flower.

Chemical

• Herbicides should only be used if mechanical control techniques are not feasible.
• Herbicides should be applied before flowering.
• Glyphosate, 2,4D or triclopyr may effectively control this plant.

Resources

Sources for content:

• Washington State Noxious Weed Control Board
• USDA, ARS, National Genetic Resources Program. Germplasm Resources Information Network -(GRIN)[Online Database]. National Germplasm Resources Laboratory; Beltsville, Maryland.
• Helmisaari, H. (2010): NOBANIS – Invasive Alien Species Fact Sheet – Impatiens glandulifera. – From: Online Database of the European Network on Invasive Alien Species – NOBANIS

Links for more information

• Invasive.org [exit DNR]
• USDA PLANTS Profile [exit DNR]
• NOBANIS – Invasive Alien Species Fact Sheet [exit DNR]
• Washington State Noxious Weed Control Board [exit DNR]