Himalayan balsam is a fast growing, tall, upright annual. Seed germinates in early spring, producing broad, almost square seed leaves that are followed by lance-shaped true leaves with finely serrated edges. Sturdy hollow stems, often with reddish tints, grow to a height of about 2m (6½ft) during summer. Scented flowers in shades of pink and purple, and occasionally white, are borne from June to November.  

Flowers are followed by elongated seed pods containing up to 16 rounded seeds approximately 3mm (⅒in) wide. Its seed is initially pale and becomes dark brown when ripe. Its root system is surprisingly small, considering the height of the top growth, with roots rarely growing deeper than 15cm (6in). The whole plant dies in autumn or early winter leaving sections of dead, straw-coloured stems lying on the ground.

Himalayan balsam is classed as a non-native invasive plant. It appears on the Wildlife and Countryside Act 1981, Schedule 9 list and the Non-native Species Secretariat (NNSS) list of Species of Special Concern, meaning there are restrictions on growing, cultivating, selling and transporting it. If Himalayan balsam is already growing in your garden, this is not considered an offence, though it is recommended that you control or remove it. However, you must not intentionally introduce it or cause it to spread.

The nectar-rich flowers of Himalayan balsam, that bloom well into autumn, make it a favourite of bees and beekeepers, but this is not enough to outweigh its negative impacts, which include:  

• Outcompeting
  A native plant is one that originated or arrived naturally in a particular place without human involvement. In the British Isles, native plants are those that were here during the last ice age or have arrived unaided since.

  native plants for space, light, moisture and nutrients. Rapid growth early in the season leads to dense, tall stands of Himalayan balsam that crowd out other plants and reduce species diversity.  
• Soil erosion along water courses. Himalayan balsam often colonises the banks of rivers, streams and ditches. Its shallow roots and annual growth habit do little to stabilise the soil along banks, leading to habitat alteration and degradation.

© Shutterstock

Himalayan balsam often grows along watercourses, where it does little to stabilise soil

Here are our answers to your most common questions about dealing with Himalayan balsam:

How

Invasive plants are those that grow vigorously, spread rapidly and can out-compete other plants. Native, non-native and cultivated plants can all be invasive.

invasive is Himalayan balsam? 

Since its introduction in 1839, Himalayan balsam has become widespread and common in the UK, primarily along riverbanks, streamsides and other damp areas. Its rapid spread is partly due to its effectiveness at producing and dispersing seed. A single plant can produce hundreds of seeds, and its explosive, easily triggered seed pods propel seed up to 7m (23 ft) from the parent plant. Seed can travel much further and colonise new areas by floating down water courses, and can remain viable for two years.

Humans are Himalayan balsam’s other main means of distribution. This might be through deliberate sharing and spreading of seed by gardeners who appreciate its ornamental qualities but are unaware of its invasiveness, or inadvertently by moving soil that contains seed.

© Shutterstock

Himalayan balsam can quickly colonise damp, partially shaded areas 

Do I need to get rid of Himalayan balsam? 

If Himalayan balsam is already growing in your garden, or on your land, and you are not intentionally keeping or cultivating it, or causing it to spread, then you are not committing an offence. However, because it is a non-native invasive species a relevant environmental authority can order control measures if they deem it necessary.

Due to Himalayan balsam’s invasiveness and the negative impacts it has on

A native plant is one that originated or arrived naturally in a particular place without human involvement. In the British Isles, native plants are those that were here during the last ice age or have arrived unaided since.

What is the easiest way to get rid of Himalayan balsam? 

To eradicate Himalayan balsam from your garden, it is important to prevent plants from flowering and setting seed. Its seed can remain viable in the soil for two years, so by using the control methods below, you can rid your garden of it within a few years.

• Hoe off seedlings and young plants – hoe on a warm, dry or windy day, so exposed roots dry out quickly and die. Check regularly for emerging seedlings, especially along the banks of watercourses where seed may arrive from upstream. 
• Cut regularly to prevent seed production – use secateurs, a strimmer, brushcutter or mower, depending on how many plants you need to cut and how easily you can access them. Cut as low as possible, ideally below the first
  This is a point on a stem where new growth sprouts, usually leaves, buds, side-shoots or roots. The section of stem between two nodes is an internode. When taking nodal stem cuttings, you trim them just below a node at the base, as this is where new roots will sprout. With a few plants, especially climbers such as clematis and honeysuckle, stem cuttings produce roots from the internode, so are known as internodal cuttings.

  node on the stem to reduce regrowth and branching. It may be necessary to cut back plants up to three times during the
  The period of time when an individual plant is in active growth. This will depend on the local climate and light levels, and can vary between different plants, although it is broadly from spring to autumn.

  growing season to ensure they don’t flower. This method limits soil disturbance.  
• Hand pull – grasp a lower section of stem and pull out the whole plant along with the root system. This is easiest in spring and early summer when plants are still relatively short. It is still feasible to pull out taller plants during summer, but this should be done before they start flowering.  
• Fork out plants – if you find it difficult to remove the roots by hand pulling, use a hand fork on small plants and a border fork on larger plants. Fully insert the tines to the side of the main stem and lift out the roots.   
• Smother seedlings – on ground that is level or with only a slight slope, cover the soil in late winter/early spring with a compostable material, such as cardboard, and then a 10-20cm (4-8in) thick layer of organic matter. Alternatively, use a heavy grade
  Anything that can be decomposed by fungi, bacteria and micro-organisms, so it doesn’t persist indefinitely in the environment. Biodegradable plastics are usually made from plants, such as bamboo, rather than fossil fuels. Ideally, products that claim to be biodegradable should break down quickly and leave nothing harmful behind. However, they may need specific conditions in order to biodegrade successfully or may produce greenhouse gases such as methane in the process.

  biodegradable
  Mulch is a layer of material, at least 5cm (2in) thick, applied to the soil surface in late autumn to late winter (Nov-Feb). It is used to provide frost protection, improve plant growth by adding nutrients or increasing organic matter content, reducing water loss from the soil, for decorative purposes and suppressing weeds. Examples include well-rotted garden compost and manure, chipped bark, gravel, grit and slate chippings.

  mulch matting – this would be suitable for sloping ground. Keep soil covered for a few years, topping up the mulch layer if necessary, so no viable seed remains.    
• Hire a specialist weed control contractor – if you are unable to control Himalayan balsam yourself, consider using a reputable company that specialises in the removal of invasive non-native plants. The organisations below have lists of these contractors. ​

How should I dispose of Himalayan balsam?   

Himalayan balsam (and soil containing its seed) is regarded as 'controlled waste' under the Environmental Protection Act (Duty of Care) Regulations. If possible, destroy plants on site. If removal is necessary, the Environment Agency needs to be informed and you must use a registered waste carrier and an authorised disposal site. Contact the Environment Agency or your local council for information on authorised sites. If you use licensed contractors, ensure they use registered disposal sites and provide copies of waste transfer permits.

The following government websites provide more information:  
Treatment and disposal of invasive non-native plants: RPS 178  
How to stop invasive non-native plants from spreading  

Do not put Himalayan balsam in your home compost, council

Plant-based waste that is suitable for composting, such as dead leaves, clippings from pruning or grass mowing and discarded annuals. Many local councils have green waste recycling schemes if home composting isn't an option.

Should I use weedkiller? 

No – although Himalayan balsam is an invasive non-native plant, it can be controlled by using non-chemical methods. It is often found

Transferring young plants from one container to a slightly larger one, where they will have more room to grow and fresh potting compost. This encourages continuous, healthy growth.

The RHS does not support the use of weedkillers and recommends that alternative control methods are used. However, when invasive plants are a threat to

The variety of living organisms (plants, animals, fungi and microorganisms) in a particular environment. Boosting the biodiversity of your garden has many benefits, including supporting wildlife, improving soil health and reducing the likelihood of pest and disease problems.