Himalayan Balsam

As its name suggests, Himalayan balsam is from the Himalayas and was introduced here in 1839. It now an invasive weed of riverbanks and ditches, where it prevents native species from growing.

Himalayan balsam is an invasive weed that, if not removed, can take over a garden and choke out other plants.

This blog post will provide an in-depth guide on what Himalayan Balsam are, how they grow, and how to eradicate them from your garden.

Quick Facts

Common names: Indian balsam, policeman’s helmet, bobby tops, copper tops, kiss-me-on-the-mountain, gnomes hatstand, jumping jack
Scientific name: Impatiens glandulifera Royle (I. roylei)
Family: Balsaminaceae
Origin: non-native
Flowering season: June to October
Habitat: river banks, ditches, damp meadows, woodlands, grassland, farmland, wetlands, gardens or areas close to water or waste

Himalayan Balsam Identification

Himalayan Balsam is often found in damp soil areas such as along river banks where it forms continuous stands, it can also be found in damp woodland.

It spreads quickly and forms dense thickets, altering the ecological balance and character of wetland habitats.

Himalayan balsam flowers come in multiple shades but all resemble the same shape
Himalayan balsam flowers come in multiple shades but all resemble the same shape

What does Himalayan Balsam look like?

Characteristics that make up the Himalayan Balsam leaf, stem, root and flower are detailed below.

Considered one of the most invasive weeds within the UK, it is essential to identify and remove it swiftly as it spreads quickly.

Leaves: Lanceolate with red veins and serrated with a red tinge at the edges. He leaves are dark green with serrated edges. 5 to 23 cm (2.0 to 9.1 in) long.

Stems: It is the tallest annual plant in Europe reaching heights of 2 to 3 metres.

The stems are pale green to yellow and hollow, smooth and hairless with a red tinge.

Himalayan Balsam can often have red roots extending from the stem down toward the ground.

Roots: Spreading through a network of rhizomes, Himalayan Balsam covers a large area quickly, but thankfully the roots are shallow. Its hardy root system has the ability to break its way through asphalt and concrete.

It has no roots just one big stem buried in the ground from which it sucks up all its nutrients.

The Himalayan balsam flower which shape justifies its common names
The Himalayan balsam flower which shape justifies its common names

Flowers: Visible in different hues of white, pink and purple clusters of tiny flowers which are very ornate with a hood-like shape.

The Himalayan balsam pods containing hundreds of seeds
The Himalayan balsam pods containing hundreds of seeds

Seeds: The explosive seed pods are thinly kite-shaped and green with red veins. The seeds start off white becoming black and eventually very hard.

The seedpods are dehiscent and explode when touched or shaken. The seeds are expelled up to 7 m from the parent plant. The seed is transported by water but can also be carried in mud by animals and man. 

Seeds are set from August to October. There are 4-16 seeds per pod and each plant can produce 800 seeds.

The Problem

The plant is an invasive weed that needs to be managed before it overruns an area.

Himalayan Balsam Seasonal Changes

Himalayan Balsam quickly sprouts in the vegetation and duplicates quickly, covering the site. On river banks, the seeds are spread via water and the plant quickly duplicates along the banks of the river.

Himalayan Balsam in Spring

Beginning its rapid growth from seed to flower happens in just a few short months.

Acting fast and apply herbicides to the plant foliage in the spring before flowering occurs.

Himalayan Balsam in Summer

Between June and October, it produces clusters of purplish-pink (or rarely white) helmet-shaped flowers.

By June it is the best time to cut the weed before it flowers. Use a scythe, machete, flail or strimmer to carry this out. Remember to cut it below the first node to prevent regrowth.

At full bloom, Himalayan balsam grows up to 3 feet
At full bloom, Himalayan balsam grows up to 3 feet

Himalayan Balsam in Autumn

With leaves dying back to a yellow-brown colour and the stems turning brown, the weed has almost completed its annual cycle. Only the roots and seeds will remain in order to return for the following year.

Himalayan Balsam in Winter

Due to its rapid growth, it shades out most of our native species and can leave river banks bare and exposed to erosion in the wintertime.

When the plants die down in winter they leave large bare areas that are sensitive to erosion.

Himalayan balsam grows on waste ground easily
Himalayan balsam grows on the waste ground easily

How to get rid of Himalayan Balsam

Traditional ways of controlling the plant, either by pulling it up or spraying it with chemicals, don’t or can’t always work, because the plant often grows in difficult to reach places and delicate river sites.

Method One – Herbicide Treatment

Where non-chemical control methods are not feasible, chemical controls may need to be used. Choose a weed killer that is most appropriate for the purpose by reading the label carefully before buying or using it.

Contact weed killers and glyphosate have low persistence in the soil, being virtually inactivated on soil contact.

Residual weedkillers persist in the soil for several weeks or months and can move deeper or sideways in the soil, leading to possible damage of underlying plant roots.

Take care when applying weed killers near ornamental plants. Cover them with plastic sheeting while spraying, and only remove it once the spray has dried on the weed foliage.

Fatty acids, acetic acid and pelargonic acid

The non-selective contact weedkillers acetic acid (Weedol Gun! Fast Acting, Ecofective Spot-On Fast Acting Weedkiller, ResolvaFast Weedkiller, Vitax Garden Weedkiller), fatty acids (SBM Solabiol Super Fast Weedkiller) or pelargonic acid (Doff 24/7 Fast Acting Weedkiller, Neudorff Weed-free Plus, Westland Resolva Xpress Weedkiller, Roundup NL Weed Control) can be applied before flowering.

Glyphosate

Himalayan balsam can be controlled with a weed killer based on glyphosate (e.g. Roundup Fast Action, Westland Resolva Pro Xtra Tough Weedkiller, SBM Job done General Purpose Weedkiller or Doff Weedout Extra Tough Weedkiller).

Glyphosate is a non-selective, systemic weed killer that is applied to the foliage. It is inactivated on contact with the soil, so there is no risk of damage to the roots of nearby ornamentals, but care must be taken that the spray doesn’t drift onto their foliage.

Used with care, glyphosate is safe to use around the base of non-suckering woody plants, as long as the bark is woody, brown and mature. Glyphosate is most effective when weed growth is vigorous.

Treat Himalayan balsam at the early flowering stage to ensure the weed is knocked back before it has a chance to self-seed.

Ground cover of this weed spreads far and wide
Ground cover of this weed spreads far and wide

Method Two – Digging it out

Cutting the Himalayan Balsam below the lowest node of the plant is also an option, but mostly Balsam is pulled from the ground by hand.

This manual method is easy because the plants have shallow roots, but this is very time consuming and needs to be done in the small window of time from when they first come up, to before they start to flower and seed.

Repeated mowing will prevent it from over-shading other vegetation. Plants should be cut to ground level by the end of June and before the plant flowers.

Earlier cutting results in rapid regrowth of new stems that will flower and set seed. Cutting above the lowest leaves stimulates the axillary buds to regrow.

Disposal of the weed

Cut stems can be left on-site to decompose in an open area. It is best to avoid taking the plants off-site for fear of cross-contamination.

To ensure this is carried out cleanly and efficiently dispose of the weed by placing them in a bin to avoid the seed from spreading.

Management of Himalayan Balsam

To stop Himalayan Balsam’s prolific spread there needs to be catchment scale, widespread control, which needs to be repeated in order that seeds in the seed bank cannot just repopulate the areas that have been cleared.

The seeds only survive for up to 18 months so it is estimated that Himalayan Balsam can be removed completely from an area within 2 years if repeated control efforts are made and there is no re-introduction of the plant from nearby sites.

It may take a couple of seasons to obtain good control of Himalayan balsam, as additional weed seedlings germinate after the parent plants are killed off.

After removing, it is important to re-establish native species of plants. This will help to achieve control, reduce soil erosion and provide competition for Himalayan balsam seedlings.

Cutting it back will manage the population but if it is not killed it will just force the plants’ energy into rooting deeper. A targeted herbicide application is the only way to really control it for good. 

In Conclusion

We hope this article has helped shed some light on the dangers of Himalayan balsam so that you can better protect both yourself and your home.


How does Himalayan Balsam spread?

It spreads via its seeds.