Himalayan balsam, Impatiens glandulifera, is a member of the balsam family (Balsaminaceae).
Himalayan balsam originates from the Western Himalayas.
It was introduced to Canada in the early 1900s as an ornamental garden flower.
It is now considered a pest in many countries throughout the world. It can be seen along several trails and roadsides in Prince Edward Island.
Himalayan balsam is fairly easy to identify, especially if it is still in flower. Here are some distinguishing features you can look for.
Can grow to be 2m tall
Red bamboo-like stem
Distinct flower with sac structure
Flowers are deep pink to white
Flowers bloom from June– October
Seed pods is are tear-drop-shaped and the slightest pressure will cause them to explode and release seeds
Leaves are long, slender, sharply-toothed, and arranged oppositely
Forms large, dense, stands
What it does in the ecosystem
Himalayan balsam exhibits a high reproductive rate through prolific seed production (up to 2500 seeds per plant).
The plant’s seed pods explode when disturbed, shooting seeds out to a distance of up to seven metres from the plant. An alternative common name is touch-me-not, indicating the plant’s sensitivity to touch and explosive seed dispersal.
The typical habitat for this plant is nearby water, allowing its seeds to spread quickly and over great distances.
Seeds can germinate underwater.
Himalayan balsam germinates earlier than many native plants and forms dense patches, preventing native plants from establishing.
In addition, it has a weak root system. The combination of weak roots and out-competing native ground cover means that when the plant becomes established in riparian zones it can increase erosion.
The flowers produce floral nectar that attracts bees, competing with native plants for these pollinators.
Himalayan balsam can secrete allelopathic chemicals, which inhibit the growth of other plants in a local area.
Its stems are high in polysaccharides, which makes them more resistant to decomposition, so when the stems die and fall over they can suppress the growth of native species the following year.
Before you decide which control method you are going to use, consider the following:
Since this species often occurs along watercourses, it is recommended that all control efforts first be focused on upstream populations, to avoid downstream spread.
The size of the infestation.
The amount of effort you are able and/or willing to expend. Often, multiple control methods are used simultaneously. Ensure that you also consider the local ecosystem and what other organisms or ecological processes may be affected by management.
Timing is crucial for the management of Himalayan balsam. Manage the plants in the spring and early summer, before seed set. Seeds begin to appear in August. If management is attempted after seed set, you run the risk of dispersing seed during management, which is the plant’s primary method of reproduction.
The best method for removal of Himalayan balsam is pulling since the roots are weak and the plants can be easily removed.
Pulling should occur before plants go to seed in mid to late August.
Himalayan balsam seeds are contained within seed pods that, when mature, will explode when touched, dispersing seeds, and perpetuating the infestation.
If pulling must occur after the plants have gone to seed, carefully remove seed pods before plants are pulled. Do this by gently cutting the stem below the seed pods, and immediately place the stem and seed pods into a garbage bag.
Alternatively, place a bag over the entire plant and cinch it shut near the plant’s base, ensuring that all seed pods are contained in the bag. Pull the plant up. This will keep all seeds within the bag and prevent dispersal.
Pulling must be repeated for several years because seeds in the ground remain viable for multiple years.
Mowing stands of Himalayan balsam is an effective control method.
The area must be mowed repeatedly to guarantee full mortality.
Mowing should be done as soon as flowers appear, to reduce the chances of seed development.
If hand cutting, cut the plant at ground level and repeat annually, but if you are hand cutting you should likely just pull the plants out unless you are worried about exposing the bare soil.
The PEIISC does not provide advice on chemical control measures at this time.
If you are using chemical controls, it is imperative that all local legislation and manufacturer’s instructions be followed.
The herbicides may damage surrounding vegetation and their use is prohibited within the 15-metre buffer zone surrounding wetlands and watercourses in PEI.
Studies have shown that Himalayan balsam plants treated with herbicide during flowering were still able to produce seeds and therefore continue to spread.
DISPOSAL + FOLLOW-UP
To prevent spread during the management process, all plant material should be collected, bagged, and prepared for proper disposal.
Each time you manage the site, collect, bag, mark, and dispose of all plant parts properly.
Bag the plant material in clear plastic bags.
Mark the bags boldly with a permanent marker. Write “INVASIVE PLANT” or “HIMALAYAN BALSAM” on the bags.
If you have a place away from foot and wildlife traffic, you can dry out the material, making it much easier to move.
Leave the bags open and in the sun for a week to dry.
Only do this if you can guarantee that the plant will not be spread from where it is drying.
Never do this if seed pods are attached, they may spring out of the bag by explosive force.
If the bags are thin, double bag them to prevent accidental dispersal later on.
Tie the bags tightly and place them in your usual residential waste collection (THE BLACK BIN)
Never place invasive plants into the compost. This may allow them to become established once they reach the heap.
For loads larger than what would fit in your residential waste collection, reach out to the PEIISC for specific disposal instructions.
All equipment used should be cleaned before leaving the site, and all plant parts should be removed from your person, tools, and vehicles.
Control measures should be repeated in the following two growing seasons to ensure complete eradication.
After two years, you may see success, as the seeds cannot survive in the soil longer than 18 months.
Removal of Himalayan balsam in riparian areas may lead to erosion. Soil stabilization measures such as geotextiles use or mulching may be necessary.
Reach out to the PEIISC for specific disposal instructions.