Industry | 2009.05.18
The 15 plants killing our countryside
Rogue species of rhododendron, hyacinth and waterweed may be banned from sale
Garden centres and nurseries could be banned from selling several popular plants under new measures being considered by the government to control alien species invading the UK.
Top of the list are a number of varieties of pond weed used as oxygenators in garden ponds. Having escaped into the wild, they are now overwhelming waterways throughout the country. Rhododendron ponticum, which has colonised woodlands since being introduced as an ornamental plant in 1793 to Kew Gardens, is also earmarked because of the potential impact it has on native flora and fauna, including the dormouse.
In all, 15 species are named in a consultation by the Department for Environment, Food and Rural Affairs, despite protests that some of the plants are so widespread that stopping further sales will make no difference. Rhododendron growers and retailers are particularly concerned, saying it is not clear whether any ban would cover hybrids or variants of rhododendron ponticum, which would have a significant economic impact.
While rhododendron ponticum is not commonly bought for gardens, it is abundant on large estates, being particularly useful for game cover. However, the plant is widely used as rootstock, for grafting many hundreds of hybrid varieties.
If such hybrids were also to be banned, the law would have to be phased in over several years to allow growers to develop different methods of propagating popular ornamental varieties, say experts. The Horticultural Trade Association said one leading rhododendron grower was producing more than 1,000 plants of various cultivars which used ponticum as an understock. That business would lose £20,000 a year.
Tony Dickerson, horticulture adviser at the Royal Horticultural Association, warned that one of the major problems in implementing any sales ban was that plants were often not correctly labelled in garden centres and nurseries.
Keith Davenport, chief executive of the Ornamental Aquatic Trade Association (OATA) said that banning Canadian waterweed, a plant routinely found in garden and aquatic centres, was "not likely to have any impact". Brought in by the timber trade, it had since been spread by boats, currents, vehicles and anglers, and was now found almost everywhere. He said: "It\'s a bit like shutting the stable door after the horse has bolted, run round the paddock five times and galloped off yonder." Davenport argued that banning Canadian waterweed, along with Nuttalls waterweed and curly waterweed, would cost the industry between £2m and £5m in annual sales.
The water hyacinth, a showy plant with light blue to violet flowers, is also on the list. Annual sales are worth around £1m. But there is opposition to banning its sale, not least because experts say that as a tropical plant it is not hardy enough to survive in the UK and therefore cannot be considered invasive. "It would take phenomenal climate change for that to survive our winters," said Dickerson.
The DIY and gardening chain B&Q said it did not stock any of the 15 listed plants and fully endorsed the proposal to ban them. But the Environment Agency has cautioned that publicity on any ban on sales would have to be handled extremely carefully as there was a risk it might exacerbate the problems.
"In banning the sale of certain water plants for use in aquaria and garden ponds, alternative native plants will need to be promoted and marketed," it told Defra. "There is a danger that publicity will result in a sudden upsurge in problems caused by householders or businesses getting rid of these plants already in their aquaria, ponds or gardens. Care will be needed in managing this, particularly in relation to attractive or popular plants such as Canadian pond weed and parrot\'s feather." The government will make a decision on the future sales of these plants later this year. The National Council for the Conservation of Plants and Gardens said it could mean barriers to conservation activities, and the National Farmers\' Union said Defra should compensate growers for loss of the wholesale market value.
Unwelcome intruders
Carpobrotus edulis - Hottentot fig
From South Africa, has large magenta or yellow flowers and spreads along cliffs.
Allium paradoxum - Few-flowered leek
Aromatic plant which has some culinary uses.
Rhododendon ponticum
Has colonised woodlands and is vulnerable to sudden oak death.
Fallopia japonica - Japanese knotweed
First introduced by Victorian collectors as desirable for its exotic appearance.
Impatiens glandulifera - Himalayan balsam
A relative of the busy Lizzie, introduced to the UK in 1839.
Eichornia crassipes - Water hyacinth
This popular plant is said not to be able to survive our climate.
Azolla filiculoides - Water fern
Native of the Americas. Introduced as a decorative ornamental plant in 1840.
Myriophyllum aquaticum - Parrot\'s feather
Widely grown in small garden ponds. First found in UK in 1960. Native to South America.
Hydrocotyle ranunculoides - Floating pennywort
Brought from New Zealand to stock aquariums and garden ponds.
Gaultheria shallon - Shallon
An attractive thicket-forming evergreen shrub from west coast of North America.
Crassula helmsii - Australian swamp stonecrop
Introduced to Britain in 1911 from Tasmania as an oxygenating plant.
Ludwigia peploides - Water primrose
Has caused major problems on the continent as well as areas of the UK.
Elodea canadensis - Canadian waterweed
Has become so naturalised that local species have adapted to feed on it.
Elodea nuttallii - Nuttalls waterweed
Popular and sold as an oxygenator.
Lagarosiphon major - Curly waterweed
Sold as an oxygenator for ponds.
For more information, please visit
http://www.guardian.co.uk/uk/2009/may/17[...]s-pond-weed-rhododendron-defra
