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Invasive Garden Plants

Nowadays the chances of finding species alien to these shores are greater due to an increase in the movement of plant materials. A recent study has found that the incidence of alien pests and diseases in the UK has increased from about 150 per year in the 1970's to about 370 in 2003. More and more fruit and vegetables are imported from all over the world and they can easily give the interlopers a lift, eg. the spiders used for pest control on vines have been found in bunches of grapes. Plants are also raised overseas where the climate is better and labour is cheaper, eg. bedding plants in Israel and indoor plants in Florida.
Some imported material is supposed to have a "plant passport" or be declared, but most plants and trees are not checked for eggs or hidden animals. The increase in winter temperatures here could mean that these visitors will become established in the wild. Even non-organic materials can bring unwanted species, the Asian Hornet is spreading from Southern France after it is believed to have arrived there in a consignment of pots from China - they are very aggressive preying on Honey Bees and have caused some human deaths as well.

Taking any organism from one place to another is unpredictable as the new environment is unlikely have any of the natural controls acting on it where it came from.

Here are some examples which have been recorded recently:-

Many of the trees, shrubs and weeds around were introduced hundreds of years ago, little thought was given to the consequences. Some of the more wayward of the ornamental plants in the garden have liked it so well that they have moved beyond the flowerbed and are now regarded as weeds. Others have been here for so long that they are considered as native, eg. Beech, Sycamore and most of the conifers.

There are some introductions which have naturalised and are becoming a nuisance as they overwhelm native plants.

Some of the larger animals were brought for food, fur or just ornamental purposes and are now roaming free.

It can be seen from these examples that introducing an alien species, whether deliberately or accidentally can have far-reaching consequences. No species can be introduced to-day without extensive research. Some are being tested for use as biological controls of pests and diseases, many of which are due to careless releases in the past.


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