Research
RHS Science Exchange
What cost the world in your garden?
How great is the threat to our native and garden flora from the
accelerating international plant trade?
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Transcript of speakers' videos
Clive Brasier, Emeritus Mycologist at Forest Research and Visiting Professor at Imperial College
Many of us are concerned about the current international plant trade because it is growing so enormously. For example, in the UK imports of live plant trade have gone up in value just over the last decade from about 400 million to about 900 million pounds per annum, so they’ve more than doubled. The reason for being concerned about this is that, of course, as imports go up, quantities go up there is a greater risk of importing exotic pests and pathogens into the country that might damage our natural vegetation. Exotic pests and pathogens are those that can come into the country and that then can start attacking our native plants or our plants in gardens that may have no natural resistance to them; and so they can cause an awful lot of damage and can maybe cause either an epidemic or in some cases act rather more insidiously, and start degrading a natural ecosystem. So the decline of that ecosystem will be gradual, but the net effect may be that a lot of the native plants and animals that live in it will no longer be able to inhabit it because it’s changing so much.
One thing that we are also seeing currently is the increasing import of plants from quite far-flung places like Australia, New Zealand and China. Even sometimes tens of thousands of plants coming in one batch. And the risk is obviously from places like that is that there may be exotic pathogens that we may know absolutely nothing about.
Because we are dealing with pathogens that are microscopic they can’t be easily seen, and those plants may look healthy but, in fact, be carrying those micro-organisms into the country.
With GM organisms which some of the public are of course concerned about, we are dealing with the insertion of a single gene out of an organism’s entire mass suite of genes which could be tens of thousands of genes into another organism and maybe a marker gene to go along with it which one could recognise as its heir. That's just a single gene people are worrying about. With invasive organisms we are dealing with an entire genome coming into the environment and perhaps polluting the environment.
These are photographs of the new fungus called box blight which is spreading on Buxus around the country, including, of course, attacking box. Now at Boxhill this is a new fungus previously unknown to science which has probably come in on imported plant stock.
Another example is the alder's Phytophthora currently spreading around Britain and much of Europe killing native alders along our rivers. A new hybrid that is now apparently able to attack alders is probably the parent species of that pathogen not able to do so.
I think time is running out. In fact, from this point of view we have to make up our minds - do we want to keep our environment in the reasonable condition its in now, or take the risk of having many new pathogens and diseases coming into the country in our natural ecosystems?
Guy Barter, Head of Horticultural Advisory Services at the Royal Horticultural Society
Gardeners are driven by a passion for plants, and the plants are the raw material they use to make their gardens and give life to their dreams and aspirations and artistic intentions. And there is a wide range of plants available in Britain. You can see the range in this nursery, it's an extraordinary number of plants - some of them growing in Britain, some of them imported; altogether there are about 74,000 plants at least offered to gardeners in Britain; that's 74,000 listed in our RHS Plant Finder . And this wide range of plants that gardeners thrive on and the garden industry needs, are to a certain extent imported, and if they weren’t imported there wouldn’t be that choice.
I think gardeners are unaware of the risks posed by these large plants and imports of plants because there is no real guidance on the plants you buy as to where they come from.
Trade views the current plant health framework as a necessary evil. Clearly from the number of pests and diseases that have come to Britain in the last 50 years there has got to be very careful and stringent control at the borders. The advantage of being an island is that we can actually do this in the way that continental countries can’t. In recent years there has been things like anthrax attacks in America, terrorist attacks in Europe and America and there has been the foot and mouth disaster, when a disease got in and spread through British livestock. So I think there is much more awareness of the risks and clearly if there was an outbreak of any particular damaging disease and in particular one that would attack British native trees, as the recent sudden oak death attack has done, then it would be extremely adverse implications for the horticulture trade’s reputation as well as being an environmental disaster.
But there also is deep perception that if plant health regulations are enforced too enthusiastically, then that would add an unfair cost and burden to British growers. So it's a question of finding a balance.
And what we want to do is keep this range of plants so the horticulture industry can thrive.
I believe given our island’s status and our state of knowledge about many pests and diseases, it's possible to have plant health import regulations and procedures that will actually allow us to have a thriving horticulture trade and have a high level of security.
The plant trade has got a great future - it's constantly evolving in the face of changing demands from gardeners.