What is Himalayan balsam?
Himalayan balsam (Impatiens glandulifera) is a tall, annual weed that grows so vigorously it's classed as an invasive non-native plant species. Native to the Himalayas, it was originally introduced to the UK as a garden plant but quickly spread into the countryside and is common along watercourses. Himalayan balsam is a major concern because it out-competes native plants, thanks to its exploding seedpods, which disperse seeds over a wide area and into water.
The distinctive hooded shape of Himalayan balsam flowers has given rise to the popular common name of policeman’s helmet. Other common names include bobby tops, copper tops and Indian balsam.
How to identify Himalayan balsam
Himalayan balsam thrives in damp soil and is found alongside waterways, in marshes, and damp woodland edges. Plants can grow a height of up to 2.5m. Leaves are lance-shaped, mid- to dark green, with red veins and serrated edges. The stems are hollow and hairless and are green or yellow-green and tinged with red. Flowers are borne in summer and can be pink, purple, or occasionally white, and have an unusual, hooded shape. These are followed by green, kite-shaped seed pods which are red-tinged. When ripe, the seed pods ‘explode’ and spread the seed as far as seven metres from the parent plant. Himalayan balsam completes its life cycle within one year and dies in autumn.
Is Himalayan balsam a problem?
Himalayan balsam is a problem plant and very invasive in the UK. In many areas the whole ecological balance of the landscape has been altered by Himalayan balsam and it's regarded a huge problem by ecologists. Its height, ease of spread and density of growth, along with its ability to grow in low light levels, means it rapidly out-competes native plants. Also, because Himalayan balsam is so popular with bees, it's thought that other plants may receive less pollination as a result. Himalayan balsam also contributes to erosion problems on river banks because growth disappears in winter, leaving bare soil vulnerable to high rainfall events.
Himalayan balsam is not dangerous to people or animals, and indeed the flowers, foliage, and seeds are edible. Use the young leaves and flowers in salads and the older leaves in soups and stews. Seeds are also edible and have a nutty flavour – collect these by carefully putting a paper bag over the ripe pods and gently shaking it so they explode. Wear glasses when collecting seed to protect your eyes from the exploding seed propelled from the pods.
Is growing Himalayan balsam illegal?
Himalayan balsam is listed on Schedule 9 of the Wildlife and Countryside Act in England and Wales and it's on the Government's list of Invasive Non-Native Plant Species of special concern. While it's not an offence to have Himalayan balsam already growing in your garden, it is an offence to plant or otherwise cause to grow it in the wild. It is also banned from sale in the UK. You should stop Himalayan balsam spreading from your garden and avoid accepting gifts of these species.
How to prevent Himalayan balsam
Remove Himalayan balsam as soon as it is seen and identified. Removal of Himalayan balsam before the seed ripens is crucial in its prevention. With regular checking and removal of new seedlings, it's possible to completely eradicate Himalayan balsam within several years. Dispose of cut plant material in situ or burning. Do not compost Himalayan balsam or put in your garden or household waste bin, as it's classed as ‘controlled waste’. Contact your local council for advice if you need to dispose of plant waste.
How to control Himalayan balsam
Himalayan balsam is a shallow-rooted annual and as such is relatively easy and effective to control by hand weeding, though its abundant and vigorous growth means that controlling it can be a major task. Using the chemical weedkiller glyphosate is another efficient method of control to turn to if there is no alternative, though this is best done by a licensed contractor, especially if plants are growing adjacent to water where additional regulations on chemical use apply.
How to remove Himalayan balsam
Himalayan balsam is a shallow-rooted annual, so is relatively easy to control, but you must not let it set seed. Simply pull up plants before they set seed, and keep checking back every few weeks to ensure no more plants have germinated. Larger areas can be strimmed regularly, again, providing this is done before any plants have set seed.
With regular checking and removal of new seedlings, it's possible to completely eradicate Himalayan balsam within three years. Compost the plant material unless seeds have developed, if seedpods are present it's better to burn the material.
Frequently asked questions
Is Himalayan balsam as bad as Japanese knotweed?
While Japanese knotweed and Himalayan balsam are both invasive non-native plant species, Japanese knotweed is much worse because it's perennial, and the roots are extremely vigorous and wide-spreading.
What to do if you see Himalayan balsam?
On your own land, control Himalayan balsam as soon as you see it. If you see it growing in the wild, inform the landowner as they may not be aware of its presence. You can help tackle Himalayan balsam by getting involved in local conservation working groups, which have special working party days dedicated to Himalayan balsam removal.