Himalayan Balsam - Impatiens glandulifera

While pleasant in appearance (fig. 1), the Himalayan balsam plant is classified as a weed and a pest in many countries. Where present, it can wreak havoc on the natural health of an area, outcompeting other species and damaging the stability of the soil. 

Native range and Distribution:
As in the name, Himalayan Balsam is native to the Himalayas, specifically to Western and Southern regions (NNSS, 2019). It is known to have been first introduced to the UK through its intentional planting in Kew Gardens near London. Thereafter, it spread through the UK by intentional garden planting leading to its natural and rapid spread to wild areas (NNSS, 2019). As it stands, the species is found up and down the UK (fig. 3.), with its most dense populations in England and Wales. In the Grampian area specifically (fig. 2), the species is commonly found along riverbanks and in settlements such as Aberdeen and Cruden Bay.      Globally, the species is found throughout much of the Northern Hemisphere, and in parts of the Southern Hemisphere . It is believed that climate change warming may allow the species to become a stronger presence in more northerly locations. (Pollard, 2017). 

Habitat and Physical Characteristics: 
These plants are very tall, and very efficient at spreading. In the UK, the range of Himalayan Balsam has been expanding at a rate of 645km2 per year on average, since it first took root in the country (Pollard, 2017). They can be identified by their purple, ‘policeman’s helmet’ shaped flowers (RHS, n.d.). Himalayan Balsam is happiest in damp, slightly shaded conditions, so it is common along rivers, however it can also be found in wasteland and woodland areas (SISI, n.d.). 
It is an annual species; each plant produces up to 800 seeds (NNSS, 2019) with a high germination rate at 4/5ths (Pollard, 2017). When they are ready, the seeds capsules burst open and propel the seeds up to 7m from the parent plant’s location (SISI, n.d.). These seeds typically stay within the soil until the following spring, although may remain dormant through a full summer season and germinate in the next (NNSS, 2019). 

Impacts: 
In terms of biodiversity, Himalayan Balsam can have dreadful effects. It grows in very dense groups (fig. 5) and produces high volumes of nectar. Thus, it prevents other species from receiving both light and pollinators (SISI, n.d.). Even over winter while not in flower it can have negative effects. The roots of the species are very shallow, and thus offer little support to riverbanks. When they become dominant, this can reduce the stability of riverbanks and increase the risk of flooding (NNSS, 2019). 

Management: 
As of the Wildlife and Natural Environment (Scotland) Act 2011, it is illegal to plant or allow the spread of any NNS in Scotland (UK Government, 2011). As such, it is an offense to promote the spread of Himalayan Balsam. Total eradication of the species in the UK has been estimated to potentially cost between £150-300 Million (Pollard, 2017). While not at the scale of total eradication, there are multiple ongoing efforts to manage the Himalayan Balsam population of Scotland. 
One of the best Himalayan Balsam control methods is hand pulling. The plants are very easy to pull from the soil, and if the process is conducted for multiple years in a row, this can eradicate the species from a site (SISI, n.d.). As such, there are many organisations and community groups across the country undertaking this method. For example, in Aberdeen, the Aberdeen City Council Countryside Rangers hold regular ‘Himalayan Balsam Bashing’ volunteering events. 
In addition to hand pulling, various other mechanical, chemical and biological methods can be effective. For example, sheep and certain cattle species will happily feed on Himalayan Balsam, so can be used in areas where the terrain allows (RAPID, 2017).