It’s here. And it may be invading your property soon.
As pretty as their flowers are, you don’t want policeman’s helmet in your yard or fields.
Also called “ornamental jewelweed,” this is a handsome plant. The flowers are showy and colorful in shades of purple to pink to white. About an inch long, the interesting irregular shape of the vertically two-parted flowers looks a bit like an old British policeman’s helmet — hence the common name.
The whole plant is impressive, too: policeman’s helmet grows up to 10 feet tall and sports slender, pointed leaves with toothed margins that grow up to 6 inches long.
Policeman’s helmet (Impatiens glandulifera) prefers wet ground, such as stream edges, ditches and wetlands.
Policeman’s helmet is an annual, but, like most invasive plants, it’s expert at seed dispersal. Each plant can bear up to 800 tiny seeds in pods that burst explosively when ripe to eject the seeds up to 20 feet away. Further, these seeds can travel far in water and can germinate under water, readily spreading to distant stream banks and wet areas.
Policeman’s helmet can also root from nodes in the lower stem — another spreading mechanism when plants are uprooted or broken.
Since “handsome is as handsome does,” this is not a truly pretty plant.
The same adaptive characteristics that help invasive weeds thrive in new places and proliferate can also make them hazardous to natural systems. Without many of the controls that give natural systems their diversity, such weeds may spread to make sterile monoculture plots, out-competing or squeezing out native plants and animals. Further, the lack of local animals that will eat a particular introduced weed means that most weeds have poor wildlife value.
It doesn’t help that policeman’s helmet is an annual: after crowding out more enduring plants all summer it dies back, exposing the freshly bare ground to increased erosion during winter’s rain. The far-flung seeds sprout profusely the following spring, again growing quickly to crowd out the native competition.
Besides being attractive enough to tempt naive gardeners, policeman’s helmet uses these adaptations to spread very well all on its own: Although originally hailing from northern India and the Himalayas, policeman’s helmet is now found throughout northern Europe and much of North America. In fact, it is said to be one of the top 20 invasive species in Great Britain. (In Great Britain it’s also called “Himalayan balsam.”)
What to do?
Policeman’s helmet does have shallow roots and is easily pulled up. If you do so when there are pods on the plant, however, take care to first put a bag over the seedpod-bearing top and tie it up and cut it off so you don’t spread the seeds when you pull the rest of the plant. All parts should then be bagged up and disposed as trash. The plants can be mowed, too, but that area needs to be strictly monitored for a year to two to clean up any sprouted seedlings.
So far, policeman’s helmet has been identified for sure in the Coos watershed only on North Way Lane, near Hauser.
Think you have this growing on your property in the Coos watershed?
Please let Alexis Brickner know by contacting her at 541-888-5922 or email@example.com. As the Lowlands Restoration Projects Manager at the Coos Watershed Association, she’s tracking this plant’s intrusion to our area and working to help control it early.
Some pretty things we just don’t want to keep around.