Identify a Weed - Identifying Weeds


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Australian Swamp Stonecrop Buddleia Creeping Water Primrose Dandelion Devils Apple Dwarf Knotweed

Floating Pennywort Giant Hogweed Giant Knotweed Goldenrod Himalayan Balsam Horse Tail Hybrid Knotweed

Ragwort Rhododendron Rosebay Willowherb Tree of Heaven Water Fern Japanese Knotweed Parrots Feather

Himalayan Balsam - Weed KillerHimalayan Balsam:

Species
Impatiens glandulifera formerly called Impatiens Royiei

Family
Balsaminaceae

Common names
Himalayan Balsam, Indian Balsam, Policeman's Helmet, Jumping Jacks, Nuns, Bee-Bums, Poor man's Orchid.

Introductory History
"Orchid-lipped, loose-jointed, purplish, indolent flowers, with a ripe smell of peaches, like a girl's breath through lipstick."

The sensuous opening to Anne Stevenson's much published poem "Himalayan Balsam" is as good an introduction as any to this problematical weed. It happens to be a most beautiful plant, with its towering 3 metre stature, great translucent stems and lush leaves all topped by big flowers from deep crimson and purple right through to white. The flowers beautify industrial wetlands, and accord well with the rural riparian scene throughout the UK. Wherever the plants flower, the air is full of the hum of thousands of ecstatic bumble bees. Impatiens glandulifera"Candida" in watergardens with no outlet to a river system. This has glassy pale green stems, without purplish joints, and pure white flowers which seem to glow at dusk like garden ghosts.

Himalayan Balsam, Impatiens glandulifera, was introduced to the UK by a remarkable man, John Forbes Royle. Royle was born in India in 1799 but educated in Scotland, developing an interest in botany. He qualified as an assistant surgeon, afterwards joining the Bengal Army in 1819. He remained in India until 1831. Whilst there, he was appointed Superintendent of the East India Company's two hospitals at Saharunpur, and also Curator of the botanical gardens. He stocked these with many economically important and medicinal plants, also organising plant hunting expeditions to the mountains of Kashmir for specimens for the gardens and the herbarium collection. Amongst the plants he sent to the Horticultural Society of London, was the Himalayan Balsam, for many years known as Impatiens Roylei. The date of introduction, usually given, is 1839, though it is possible that it was earlier, during the time Royle lived in India.

Following his return to England, he published several learned books on Natural History, and held some senior scientific posts and fellowships. He died in 1858.

Once again the introduction of an invasive species is touched by a sense of romance and adventure.

It was initially supposed that Himalayan Balsam was tender, so it was originally consigned to the greenhouse as an annual flower. Of course, seed popped out of the greenhouse vents to grow in the borders outside, and was soon found to be perfectly hardy. A few more pops and hops and seeds reached the riverbank and naturalised colonies began to appear by about 1855.

Like Japanese Knotweed, it is seen as a special plant, and has gathered folk-names, amongst them, Policeman's Helmet, Poor man's Orchid, Nuns, Jumping Jacks, Stinky Pops and Bee-bums. It is easy to see where most of these names come from; - the shape of the flowers, the explosive seed-pods, all one sees of the ever-present bumble bees; but why "Nuns"? As with Japanese Knotweed, Himalayan Balsam has become so much part of the landscape that people have tried it as food. I understand that the seed pods are anti-scorbutic* and pleasantly nutty, though this is not a personal recommendation.

*Helping in the prevention of Scurvy, owing to the presence of Ascorbic acid. (Vitamin C)

Description
Himalayan Balsam is a stout annual herb to 3 metres. Stems, simple or somewhat branched; hollow, glabrous, fleshy, green; tinged red or purple, especially at the prominent nodes. Stem bases very thick, up to 8cm diameter; often fringed with fleshy adventitious roots at the lowest nodes. Leaves, opposite, in whorls of 3 to 4, lanceolate to lanceolate-elliptic, margins serrate. Size from 5-23 x 1.5-7 cm. Flowers, abundant, fragrant, from white to dark purple red, with interior bearing yellow spots. Each flower up to 4cm, in racemes of 3 or more; long pedunculate. The lower sepal pouch-like, with a spur. The upper petal, a broad two lobed standard. Fruit, a pendent glabrous green seed pod, with elastic valves; 20-30 x 4-8mm, containing up to 16 seeds.

Biology
Himalayan Balsam is Britain's tallest growing annual plant, often reaching 3 metres. It prefers moist environments, and thus has mainly colonised waterside areas in towns or countryside. It also grows quite happily away from water, but as the soils become drier, so the stature of the plant is reduced. There are dense colonies in dry gardens on the top of the Cotswolds, achieving about 1 metre; and on Surrey sand, mature flowering individuals no more than 30cm high. It is remarkable that the largest plants are able to develop in so short a time. The flowers are mainly pollinated by bumblebees, also by wasps. The copious nectar also attracts other insects including the Hummingbird Hawk Moth. The seeds which are shed from July until October, need winter chill to break dormancy. They then germinate over a short period, often during April, and grow prodigiously to be able to set seed in so short a time. The main vector of spread is flowing water, into which the seeds are flung by the explosive seed capsules. Each plant has a great capacity for seed production with some individuals producing 2,500 seeds in a lifetime. Seed viability rarely exceeds two years, and no persistent seedbank is formed.

Scope
Himalayan Balsam is continuing to expand its range, now occurring throughout the UK, much of temperate Europe and the USA, where it has a northward bias.

The genus Impatiens means impatient in the sense of hasty, referring to the explosive mechanism by which ripe seeds are hurled from the plant, to enlarge the colony or be carried away by water to fresh ground. In the case of Himalayan Balsam, seeds may be thrown 2 metres. As it is an annual, it has no other reproductive method other than seed, and thus prevention of seeding is the key to control.

Control Methods
Because Himalayan Balsam is an annual plant, it has no persistent root or rhizome system. No individual plant lives, in any case, for more than a few months. The whole future of any population, therefore, is held by the seeds, and once the seed bank is exhausted, the problem is solved. Prevention of seeding by physical means, whichever method is chosen, should be repeated for as many seasons it takes to end all germination. Under usual circumstances, eradication should be possible in three years. The size of some infestations or difficulties with access can, of course, create difficulties.
The physical means employed are grazing by animals, cutting or pulling. These last two have been dubbed "Balsam bashing".

Grazing, whether by sheep or cattle should be started about mid-April and continued throughout the growing season.

Pulling can be started as soon as the plants are large enough to handle. The shallow, fleshy root system is easy to remove.

Manual cutting needs to be carefully timed and executed. If practised earlier than the end of June, rapid regrowth to the flowering stage is likely, and seed production could actually be increased. The cut needs to be made below the first pair of leaves, so there are no axillary buds to be stimulated. In any case, cutting should be completed before the main flowering period.

Repeated mowing can also be employed to prevent seeding, and prevent over shading of native vegetation.

Chemical control by spraying in spring, when plants are at their most active growth stage, with formulations containing 2,4-D or Glyphosate is also viable where environmental sensitivities do not preclude.

Research on biological control of Himalayan Balsam, is receiving attention in the UK. The aim of this research is to test host-specific herbivorous insects and pathogens from the Himalayan home range, in the hope of finding environmentally safe biological controls. The high incidence of insect attack and disease seen in the native ranges seem to offer high promise for this research. back to top

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