Himalayan Balsam Management and Eradication Project

The Problem

Himalayan Balsam (Impatiens glandulifera) was introduced from its native Himalayan foothills to the UK as a garden plant in 1839.  It was initially cultivated in greenhouses but was found to be happy outside.  With pretty pink flowers and fun exploding seed pods, it is understandable that it was considered a desirable garden plant.  It was first recorded in the wild in Britain in 1855 (in Middlesex).  Since then it has become naturalised independently in many different places and from many different sources, with plants from India, Nepal and Pakistan.  It took about a century to take hold in this country and there was a significant increase in its frequency of occurrence between the 1962 and 2019 National Plant Atlases.  It is now found throughout lowland Britain, preferring wetter habitats, particularly alongside watercourses but also damp woodlands and similar habitats.  It has the distinction of being the tallest growing annual plant in Britain managing to reach over 3m in a single growing season.

A bank infested with balsam
A bank infested with Himalayan Balsam (image by Sue Raven)

 

But Himalayan balsam is a problematic plant.  It spreads quickly; it competes with native plants for light, nutrients, pollinators and space, excluding other plants and reducing biodiversity.  It dies back in the winter, leaving river banks bare and open to erosion.  Like most non-native plant species, Himalayan balsam arrived in the UK without any of the natural enemies that keep it in check in its native range.  Without these natural enemies, the plant has an advantage over native species and grows more aggressively than it normally would.

Balsam flowers
Nectar rich balsam flowers (image by Lewis Dickinson)

Despite the apparent benefit of the rich nectar source provided for a short period of time by Himalayan Balsam (It is thought to be the most prolific nectar producer in the UK) it has been shown that the plant has a significant adverse impact on invertebrate communities in an area giving rise to a much reduced fauna where the species has invaded an area.

As it is such a prolific nectar producer, pollinating insects preferentially visit these plants, reducing seed production in nearby insect pollinated plant species and leading to decreased plant diversity in the area.

Our solution

We are hoping to eradicate Himalayan Balsam from the rivers Flit, Hit and Ivel and their tributaries.  There has been varied levels of control through this catchment over a number of years with successful removal from some key areas such as the upper reaches of the Flit and some of the fields at Sandy but the plant remains common in several areas and as such we need to widen the extent of control to prevent re-invasion of sites upstream.

We have received funding from Anglian Water’s Invasive Species Fund, through the Cambridgeshire Community Foundation, to control the plant over large sections of these rivers during 2020 and 2021 and to widen the control via the wider network of landowners.

CCF Grant Logo

I’ve found Himalayan balsam on my land; what should I do?

Small infestations (such as those found in gardens) can easily be removed by pulling by hand.  Removal should occur before late July/ August to ensure the plants have not set seed.  Pulled plants can be composted or simply left in a pile on the bank where they will quickly breakdown – provided not too much soil has been pulled up with the roots.  Breaking the stem after pulling helps to ensure the plants don’t remain viable.

Large infestations can also be controlled by pulling but other options may be considered more viable depending on the size of the stand and availability of labour, machinery or chemicals.  Mechanical cutting using a mower or brush cutter or similar equipment can be effective on large accessible stands.  Care must be taken to cut each plant below the lowest node of the stem otherwise it will regrow.  Regular grazing can also help to control this species and cows are particularly partial to it. Himalayan balsam can also be controlled by spraying the foliage with a weed killer containing glyphosate in spring, before flowering but late enough to make sure that young seedlings are tall enough to be covered by the spray, herbicide control should be a last resort.  Control treatments should be repeated more than once in a season as the plants grow at different rates and small, easily missed plants become more obvious later in the year.

Himalayan balsam seeds can only survive for approximately two growing seasons so repeating your preferred treatment over a two-year period can be enough to successfully eradicate this plant if there is no re-infestation from upstream or adjacent sites and no plants were missed.

I want to report an infestation of Himalayan balsam

If you think you have Himalayan balsam on your land and are not able to control it yourself please let us know.  If you have spotted an infestation on someone else’s land and are worried about it then please also get in touch.

You can send us an image to confirm ID along with a date, the location and if you are or known of the landowner and we will get in touch regarding the options for control.

 

Other interesting bits of info…..

Balsam seed pods
Himalayan Balsam seed pods (image by Lewis Dickinson)

Fun with seeds.

Himalayan balsam is an annual plant, it germinates from seeds each year, the seeds seem to remain viable for only a couple of years (two growing seasons) and don’t form persistent seed banks.  The seeds are a couple of mm in diameter and the number of seeds produce by each plant is variable with between 800 and 4,000 being reported, one report has shown 32,000 seeds being produced per square metre of balsam stand.  The explosive nature of the seed pods means that, when ripe, the seeds are projected several meters from the plant (up to 7m has been reported).  The seeds can survive in water and are buoyant, allowing them to travel along watercourses and aiding the species spread along riverbanks.  The over-winter dieback of the balsam stands produces bare soil that gives the plant a head start in the next spring but is prone to erosion which can carry the seeds further along the watercourse.

 

Other Balsam Species in the UK

We have one native Balsam species in the UK, the Touch-me-not Balsam, Impatiens noli-tangere which is a rare and localised plant occurring in damp lowland woodland on stream sides and valleys, there are only a few hundred records in the whole of the UK.

We have several other non-native species of balsam in the UK such as:

Small Balsam – Impatiens parviflora

Orange Balsam – Impatiens capensis

Kashmir Balsam – Impatiens balfourii

A note on names.

The genus “Impatiens”, translates to “impatient”, and is thought to refer to its method of seed dispersal.

According to Wikipedia, the species name “glandulifera” comes from the Latin words “glandula” meaning “small gland”, and “ferre “meaning ‘to bear’, referring to the plant bearing glands.  But “glandula” is a Spanish word rather than a Latin one and the Latin word “glandis” means both a type of seed and an object thrown from a sling; so it seems likely that “glandulifera” translates to “bearing seeds that are thrown” rather than bearing small glands.

The common names Policeman’s Helmet, Bobby Tops, Copper Tops, and Gnome’s Hatstand refer to the hat shaped nature of the flowers.

Himalayan balsam, Indian Balsam and Kiss-me-on-the-Mountain are from the plant originating in the Himalayan mountains.

Ornamental jewelweed and Poor-man’s Orchid refer to its cultivation as an ornamental plant.

Jumping Jacks refers to the method of seed dispersal.

Nuns and Bee-bums are of uncertain origin but when bees are gorging them selves on nectar from the plant only their rear is visible.

Wildlife on Himalayan Balsam.

There appear to be very few native species of invertebrate that are specifically associated with Himalayan Balsam.  Many of the species that have been recorded using the plant are generalist phytophagous species or species that have been dislodged from their preferred, nearby plant host.

Some of the species more closely linked to the species are listed here, many of these are also associated with the native balsam species.

A leaf mining fly, Chromatomyia horticola

A leaf mining fly, Phytoliriomyza melampyga

An aphid, Aphis fabae

An aphid, Aphis nasturtii

An aphid, Impatientinum asiaticum

An aphid, Impatientinum balsamines

An aphid, Myzus ornatus

Elephant Hawk Moth, Deilephila elpenor

Balsam Carpet Moth, Xanthorhoe biriviata