Introduction

Himalayan Balsam is a stout annual herb which grows up to 3 m. This plant grows essentially along riverbanks and streams. But it can also be found in dry grounds though its size is reduced.

Description

Stems are hollow, jointed and quite thick – up to 8cm, and often fringed with roots. Leaves are spear-shaped, with serrated edges and reach up to 150mm long.

Himalayan Balsam is characterised by abundant flowers, from white to dark purple red, present from June to October. They measure up to 4 cm.

The flowers produce a lot of nectar: which attracts many pollinating insects.

The plant produces many seeds that generally germinate during the month of April. Their growth is extremely fast; which enables them to set seed again.

Each plant has a great capacity for seed production: some of them produce 2,500 seeds in a lifetime. Seeds remain viable in the soil for about 2 years.

It is spread by projecting its seeds up to four metres but the main vector of spread remains flowing water.

Impacts

Himalayan Balsam grows in dense stands that prevent the growth of native grasses and other flora.  In the autumn, the plants die back, leaving the banks bare of vegetation and vulnerable to erosion.

Himalayan Balsam doesn’t have persistent roots and most plants only live for a few months but future generations of Himalayan Balsam are guaranteed by the high level of seed that the plant produces. Its progression and domination of riparian areas is very hard to control.

Control Methods

Although the main vector of spread remains flowing water, eradication of Himalayan balsam can be established in three years.

Repeated pulling or cutting of the plant before it sets seed can be a successful means of eradication if carried out over several years.

Spraying herbicides during spring is also an efficient treatment.

 

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