Bloody foreigners

Yes, it’s true. Alien invaders are taking over and threatening much of our wildlife. Certain pond weeds, which are readily sold and recommended in garden centres and in gardening magazines, are jumping the garden fence and escaping into our wild ponds and waterways causing widespread ecological havoc.

Water features have become very popular recently and it’s certainly true that a pond in your garden can be hugely beneficial for wildlife. But if you put certain alien oxygenators into your pond, and even worse, if you unwittingly throw your surplus plants into local waterways, you could be helping these invaders on their destructive path.

We all know about Japanese Knotweed and Giant Hogweed, longtime successful havoc makers. Well now we’re talking New Zealand Pigmyweed, Parrot’s Feather and Floating Pennywort, to name the worst offenders (otherwise known as Crassula helmsii, Myriophyllum aquaticum, and Hydrocotyle ranunculoides).

New Zealand pigmyweed has invaded many SSSI (site of special scientific interest) areas and is threatening the existence of one of our rarest plants, the starfruit. Parrot’s Feather can grow at a rate of 15cm a day and can completely choke up waterways if left unchecked. Floating Pennywort can form dense floating mats that can grow 10cm a day. These mats have already clogged drainage channels leading to flooding.

All of these bullies can grow into new colonies from tiny fragments of stems. It’s obviously very easy for these plants to be transferred from the confines of a garden pond to the greater outdoors, not only by humans but also by animals and birds. Some are even used in aquarium tanks and can contaminate waterways through the drainage system.

Eradication of these plants is very difficult, often impossible and always expensive. Herbicides are costly and ruthless to all wildlife, not just the invading culprits. The cost of treating every contaminated natural habitat site is estimated at £4 to £5 million per year.

So what is the answer for the discerning gardener? Well, if you care about our native flora and fauna, the only answer is to avoid these invaders.

In fact the organisation Plantlife is trying to get the sale of them in this country banned completely. They’re recommending that the government includes them on the schedule 9 list which is part of the Wildlife and Countryside Act which makes it an offence, without a licence, to plant or cause to grow in the wild any plant on the list.

Currently, a species can be placed on schedule 9 only if the plant is already established in habitats in Great Britain and has been shown to cause damage to the natural environment. Having said that, even if these aquatic invaders get put onto the list, it will have relatively little effect as long as the plants are still widely sold.

So really it does rely on the consumer to make a real difference. My advice for this month is to steer well clear of these aquatic invaders and buy native plants instead. Certainly if you’re trying to attract native wildlife, you can’t go wrong. Native oxygenators such as spiked water-milfoil, curly pondweed and starwort along with floating plants such as frogbit and waterlilies are just a few to recommend.

A thought to leave you with is this quote from Plantlife: ‘invasive species are likely to be the biggest threat facing our biodiversity this century’. It’s something that all caring gardeners need to be aware of.

Stay gardening wild.

For more information about Plantlife and their activities telephone 020 7808 0100.

Illustrations: Natural Image

Articles reprinted with premission from Greenfingers.com