Control Himalayan Balsam with Roundup Pro Biactive


Himalayan Balsam, (Impatiens glandulifera), is native to the Western Himalayas and since its introduction in 1839 it has spread throughout the British Isles.

It is the tallest annual plant found in the British Isles, growing to more than 2-3 m in height. Each plant can produce 800 seeds, which are released explosively from the seed pods, travelling distances of up to 7 m. The seeds, which are also transported by water, can remain viable for up to 2 years. Hence it has rapidly colonised river banks, excluding native species by competition and forcing some areas to introduce eradication policies.

The Impatiens family is widely known by the cultivated species, often known as Bizzie Lizzies. This is their big brother !

Stems are pinky red, hollow, sappy, brittle and jointed. Branches arise from the stem joints. Leaves are lanceolate with serrated edges, stalked, shiny, dark green with a reddish midrib. Leaves can be 150mm long and are opposite or in whorls of three.

Flowers are purplish pink to pale pink or rarely white. They are shaped like a policeman’s helmet and carried on long stalks in June - October.

Seeds 4 -7 mm turning from white to dark brown or black and carried up to 16 per pod.

Control methods

As the plant is an annual, control methods hinge on the prevention of seeding.

Cutting to ground level before the end of June with a scythe or machete will prevent seed shed, but cutting too early can result in regrowth of flower heads with an even greater number of seeds!

Chemical control needs Environment Agency approval in aquatic situations.

Control with Roundup Pro Biacitve

Spraying with Roundup Pro Biactive will give excellent control. The formulation is the safest to use near water and carries no Irritant symbol on the can, so is safe to operators, animals and the environment. Spot spraying needs to applied with care to minimise collateral damage to surrounding vegetation, weed-wiping will ensure this is minimised.

Monitor sites annually for 5-10 years and re-treat to take account of newly emerged seedlings.

Rates and water volumes

Problem Dose Rate Application tips
Himalayan Balsam
(overall spray)
3 l/ha in 80- 250 litres of water Spray when good foliage has developed to a height of at least 50 cm in late spring, before the end of June.
A second treatment may be necessary if more seedlings germinate.
Himalayan Balsam
(hand-held weed wiper*)
1 part Roundup Pro Biactive in 3 parts water Useful method when working amongst desirable plants & shrubs.

Most knapsack sprayers are supplied with a set of 4 deflector nozzles giving different swath widths but all delivering 200l/ha of water at 1 bar pressure and a walking speed of 1 metre per second.

Spot treatment in knapsack

(Standard 200 l/ha nozzles)

Area Sprayed Volume of Roundup Pro Biactive Volume of Water
50m2 15ml 1 litre
500m2 150ml 10 litres
1,000m2 300ml 20 litres

*The Microwipe, hand held weedwiper is available here

For more information on Roundup Pro Biactive click here or see "Total Weed Killers"