At a Glance
- Scientific name: Impatiens glandulifera
- Annual, perennial, or biennial? Annual
- Conditions it likes best: Shade and moist soil, especially along streams
- How it spreads: Spreads primarily by seed, but it is also capable of rooting wherever the stem touches soil. Mature seed pods can explode when disturbed, sending hundreds of seeds a short distance.
- How it causes damage: Policeman’s helmet forms dense patches, especially along streams, taking the nutrients, light, and space that other plants need. After preventing other plants from growing, policeman’s helmet dies every year in April and May, leaving stream banks with no plants on them when streams have the most water. This can cause the soil on the banks to wash away, leading to poor water quality for fish and insects or stream bank collapse.
- Best time and way to manage: Pull plants in May and June, as late as flowering.
- Oregon Department of Agriculture noxious weed rank: B
- Report patches of this plant? Yes. City code lists this as a Required Eradication species. Report all sightings to Environmental Services (contact information on this page). Management of this plant is required, but free help is available.
How to Identify Policeman's Helmet
Native to India and the Himalayas, policeman’s helmet is now common along the north Oregon coast and is in scattered places west of the Cascades.
Policeman’s helmet can grow over 6 feet tall. Hot pink or pale pink flowers each have a spur that sticks out the back. All impatiens species have this spur, but in policeman’s helmet, the spur is very short and usually bent up against the back of the flower. Leaf edges are saw-toothed.
Fall–Winter. This plant isn’t seen in fall or winter.
Spring. Plants emerge generally in April and May.
Summer. Flowers generally appear in May through July. Seeds are ripe 2 or 3 weeks after flowers appear, but sometimes as late as August.
How and When to Remove Policeman's Helmet
- Manual. To control, pull plants in the spring and summer while they still have flowers. Once seedpods form, they quickly burst and spread seed. Be sure to remove all the plants.
- Herbicide. Not recommended.
- Check. Check the site for new plants at least once a year and especially for the first 2-3 years after removal.
- Replant. After a year or two of managing this plant, consider planting native or less aggressive non-native plants.
Prevention is Best Practice
Clean your boots, pets, and maybe even your tires when you finish a hike or trail ride in Pacific Northwest natural areas, or if you have invasive plants on your own property. Cleaning boots and pets keeps invasive plants from spreading to new places. Be careful when trading plants with neighbors and fellow gardeners to make sure you’re not trading this or any other plant of concern.
Be Aware of Look-alikes
There are many varieties of Impatiens, including a few natives (although not in the Portland Metro area). The plant most likely to be confused with policeman’s helmet is Himalayan balsam (Impatiens balfourii), which tend to be shorter plants (3 feet tall or less) and have white and purple (or white and pink) flowers. Himalayan balsam flowers have a longer, straighter spur than I. glandulifera, but it is a species of concern. Removing it is probably a good thing, too.
Properly Dispose of Invasive Plants
To prevent spreading invasive plants:
- Never place plants or seeds in your compost or yard debris.
- Never throw pulled plants on the ground or into the street or sidewalk.
- Put all pulled plants, bulbs, or seeds into a plastic bag and put the bag in the trash.
- Wash all garden tools and gloves.