Notes from Trenoweth

Alien Invaders

With the increasing international nature of the plant and produce trade, ecologists are reminding us of the need for greater care to avoid introducing alien plants and organisms which can threaten our native flora and crops. Rabbits in Australia and Grey squirrels here are two well-known examples, but there are many others which, though less dramatic do impact on our countryside.

Here on Scilly, we recently recorded a new pest from New Zealand attacking Pittosporum. You may have noticed the blistered and distorted leaves on some bushes. About 60 years ago the yellow Oxalis, Bermuda Buttercup, reached here having travelled from South Africa. It is now a world-wide problem and infests many of our bulb fields.

Of wider concern is wild Rhododendron from the Himalayas which now covers vast areas of the UK and by shading and poisoning the ground excludes all other vegetation. Another detested garden escape is the Japanese Knotweed which yearly claims more land and block waterways. Well know on Scilly are Hottentot Fig, Montbretia and Three-cornered leek – all invaders, and on the increase.

One may ask why certain alien plants prove so invasive. Perhaps they find the "new" climate and our ample rainfall congenial and arriving here without their normal "baggage" of pests and competitors enjoy a holiday on our shores.

One thing is certain, we should take care not to introduce any more by discarding unwanted plants, especially aquatic, into the wild environment. Scilly is, of course, made more interesting by its "whistling jacks" and Agapanthus, but two invaders we certainly don’t want are magpies and Dutch Elm Disease!


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