Himalayan Balsam (Impatiens glandulifera) is an invasive riparian plant that can displace well established native perennial species. It originates from the Western Himalayas, this area is a habitat for about 400 varieties of a genus Impatiens; the species grow at altitudes of around 1800 to 4000 metres above sea level. Himalayan balsam was introduced to the British Isles at the same time as Japanese Knotweed and Giant Hogweed in 1839 as an ornamental plant, the seeds were sent to Kew Garden in England by Dr Royle from Kashmir. It was first recorded as a naturalised invader in 1855 in Hertfordshire and Middlesex. The plant spreads rapidly, typically along river banks and other watercourses forming massive monoculture dense stands preventing other species from taking root. It has also spread in wastelands and many gardens. When it dies back at the end of the growing season the fallen stands may weaken river banks, thus promoting erosion and obstructing river flow. Thus, strong Himalayan Balsam control measures are required to stop its fast spreading.
The plant has a smooth, hollow knotted stem which can be broken easily. The stem is green or red-tinged in appearance at the beginning of the growing season and turns pink in summer. The stem height can reach 8 feet, with a diameter up to several centimetres. The leaves with lanceolate to elliptic shape of 5-18 cm long and 2.5-7 cm wide with serrated edges are arranged opposite to each other or in three to five formation. The flowers are various colours from white to pink and purple; the shape of the flower has a short spur that resembles the shape of an English policeman’s helmet. The flowers are arranged in groups of 5 to 12 individual flowers and have a strong balsam smell that attracts pollinators. The Latin genus name ‘impatiens’ meaning ‘impatient’, refers to the method of seed distribution. When ripened, touching a seed capsule causes an explosion and ejection of the seeds up to a distance of 7 metres; it is due to this ability, the plant was nicknamed Touch-me-not. Each plant produces up to 800 seeds. Most seeds survive through the winter to germinate in spring; however, there was evidence of germination of seeds two years after production.
The life cycle of the Himalayan Balsam proceeds through the following main stages:
• Germination in the period from February to March.
• Leaves in April.
• Flowering in July to October.
• Production of seeds from middle July to the end of flowering.
Himalayan Balsam is mainly spread by exploding seed pods, the seeds can travel very long distances. Humans and animals also contributed to its spread by transferring seeds.
Himalayan balsam is on the list of Schedule 9 Part 2 of the Wildlife and Countryside Act 1981. Therefore, it is an offence to plant these species in the wild, whereas growing the plant privately in the garden is permitted if proper control measures are undertaken. The plant is classed as a pest across many countries in Europe.
The concern about the fast spreading of the Himalayan Balsam that has the potential to kill the species of native flora is shared by The Telegraph.
The Daily Mail reports how a group of nature vigilantes are trying to get rid of Himalayan Balsam from a river bank in Chalford, Gloucestershire.
Desperate teenagers from a village near Durham who declared war against Himalayan balsam was reported in The Telegraph.
BBC News reported on the successful clearing of Himalayan Balsam in Ystwyth Valley in Ceredigion, Wales.
Failure to control invasive species including Himalayan Balsam in residential areas could incur a fine of up to £2500; companies may be fined up to £20000, says Mortgage Finance Gazette.
Removal of invasive alien species should begin as early as possible before the problem becomes too serious. For any action to be successful, the public should be informed about the negative impact of the plant and its rapid uncontrolled spread along waterways. Special attention should be given to informing beekeepers and owners of ornamental plants.
Himalayan Balsam can be relatively easy to eradicate by physical removal. The use of certain types of herbicides can also be very efficient in Himalayan Balsam control. However, only an approved type of herbicide such as glyphosate can be applied near watercourses. The use of 2,4-D amine may be preferable in land areas since this herbicide will selectively kill Himalayan Balsam and will not affect adjacent grasses. Note, only certified specialists are allowed to purchase and apply professional herbicides. Approval by the Environmental Agency is required to apply herbicides near or at aquatic areas.
Destruction and control measures include the removal of plants, prevention of formation and propagation of seeds. It is very important to correctly time the destruction of this plant. If you remove the plants too early, it will recover. In contrast, if removal is undertaken too late the plant will form mature seeds, which will germinate the following year. The best time to eradicate is the end of July when the first flowers appear. Due to the ability to regenerate it is extremely important to remove all plant material from the treated site. Himalayan Balsam can be easily removed by weeding, mowing or trimming. Hand pulling the plants can be used on small infestation areas. Removal measures should continue for 2-3 years unless regrowth of new plants is stopped.
Some recommendations on the use of grazing animals, e. g. sheep or cattle, for the destruction of the plant are available elsewhere.