Kill the Triffids.
Interesting.
Contrary to what Ray says, the EA in my area have ceased a slash and burn doctrine completely. They now take a very different approach when pruning is done sympathetically with the habitat.
Attributed to the Royal Horticultural Society and because I know Ray loves the detail.
Himalayan balsam (Impatiens glandulifera) is a relative of the busy Lizzie, but reaches well over head height, and is a major weed problem, especially on riverbanks and waste land, but can also invade gardens. It grows rapidly and spreads quickly, smothering other vegetation as it goes.
What is Himalayan balsam?
Introduced to the UK in 1839, Himalayan balsam is now a naturalised plant, found especially on riverbanks and in waste places where it has become a problem weed.
Himalayan balsam tolerates low light levels and also shades out other vegetation, so gradually impoverishing habitats by killing off other plants. It is sometimes seen in gardens, either uninvited or grown deliberately, but care must be taken to ensure that it does not escape into the wild.
Appearance
Himalayan balsam is a tall growing annual, 2-3m (6-10ft) in height. Between June and October it produces clusters of purplish pink (or rarely white) helmet-shaped flowers.
The flowers are followed by seed pods that open explosively when ripe.
The problem
Each plant can produce up to 800 seeds. These are dispersed widely as the ripe seedpods shoot their seeds up to 7m (22ft) away.
The plant is spread by two principal means;
The most widespread distribution tends to be by human means where individuals pass on seed to friends
Once established in the catchment of a river the seeds, which can remain viable for two years, are transported further afield by water
Control
Plants that out-compete other more desirable plants or simply invade half the garden are classed as weeds and require control. First, consider whether this can be done using non-chemical means such as pulling or digging out, or suppressing with mulch. If this can't be achieved, consider using chemical methods.
Non-chemical control
The main method of non-chemical control, and usually the most appropriate, is pulling or cutting the plants before they flower and set seed. Conservation authorities regularly organise ‘balsam bashing’ work parties to clear the weed from marshland and riverbanks.
Chemical control
Where non-chemical control methods are not feasible, chemical controls may need to be used. Choose a weedkiller that is most appropriate for the purpose by reading the label carefully before buying or using. Contact weedkillers and glyphosate have low persistence in the soil, being virtually inactivated on soil contact. Residual weedkillers persist in the soil for several weeks or months and can move deeper or sideways in the soil, leading to possible damage of underlying plant roots.
Before using weedkillers alongside waterways it is necessary to contact the Environment Agency (see telephone directory for your local office). It can advise on suitably qualified contractors, as can the National Association of Agricultural and Amenity Contractors.
Take care when applying weedkillers near ornamental plants. Cover them with plastic sheeting while spraying, and only remove it once the spray has dried on the weed foliage.
It may take a couple of seasons to obtain good control of Himalayan balsam, as additional weed seedlings germinate after the parent plants are killed off.
Acetic acid, diquat, fatty acids and pelargonic acid
Alternatively, the non-selective contact weedkillers acetic acid ( Doff Fast Acting Natural Weed Spray), diquat (Weedol 2), fatty acids (Advanced 3 Hour Weedkiller), pelargonic acid (Weedol Max) can be applied before flowering.
Glyphosate
Himalayan balsam can be controlled with a weedkiller based on glyphosate, such as Roundup or Tumbleweed. Glyphosate is a non-selective, systemic weedkiller that is applied to the foliage. It is inactivated on contact with the soil, so there is no risk of damage to the roots of nearby ornamentals, but care must be taken that the spray doesn't drift onto their foliage. Glyphosate is most effective when weed growth is vigorous. Treat Himalayan balsam at early flowering stage to ensure the weed is knocked back before it has chance to self-seed.
Interestingly, our very own native stinging nettle is even more effective at taking over ground to the total detriment of other native species. But stinging nettles are in massive decline nationally (due almost entirely to loss of favourable habitat as in waste land etc simply because we English are obsessed with building on every scrap of land available) The decline in stinging nettle habitat is thought to have brought about the national decline in butterfly populations as the stinging nettle is a favoured habitat for egg laying butterflies. Frankly I'm not convinced but there is no doubt that our native nettle has the capacity to match Himalayan balsam in the aggressive take over stakes. Our native Ivy (Hedera helix) is another pretty aggressive plant. When Hedera helix goes on the march be that up trees and especially overland it will completely cover areas of the woodland floor when nothing else grows through it. Brambles are another aggressive "woody weed" which can take over the neighbourhood as is Wild Honeysuckle. Problem is however, most invasive plant species have their "secondary" uses that benefit other forms of wildlife.
Regards,
Lee.
