Gardening
What do we mean by exotic plants? When we talk about exotic plants, it simply means those that are not native. Historically, here in the UK there has been a drive to promote the planting of native trees and shrubs, provided the provenance is known, because of the risks of pests and diseases. The danger is lower when growing seed that has been harvested from trees grown here. The young plants tend to be more resilient and they display a better ability to adapt. Imported seeds, plants and trees carry a risk of introducing alien pests and diseases into the UK, against which our native species have no natural defence. There is, however, a problem with the long-term biosecurity of our UK trees. Did you know there are now only around 30 truly native species, plus subspecies and hybrids that have naturalised themselves here? The term ‘native’ is generally defined as trees that established themselves in Britain around 10,000 years ago. This was the end of the last ice age, at a time when the English Channel was gradually forming. Plant hunters began collecting specimens from around the world during Roman times. The activity saw plants introduced into Britain and this gradually opened the window for pests and diseases too. The
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Ages of Discovery and Enlightenment saw more and more explorers setting off around the world and bringing back unusual plants, in addition to teas, food, spices and animals. Many of the living species ended up in private collections or in botanical gardens. This extended the range of plants within the UK, and we have come to love and admire many of these introduced species. The glorious Liquidambar, or sweet gum, for example, is native to Asia, parts of the Mediterranean and North America. Many acer trees originate not only from Japan but also from China and Korea. The tulip tree, Liriodendron tulipifera, hails from North America, and many of the flowering cherries originate from Japan, China and the USA. Even apple trees have an exotic history! The original ancestor of many modern apple cultivars can be linked back to an ancient apple: Malus sieversii. This wild apple is native to the mountains of Kazakhstan in Asia, where they can still be found today. It’s not surprising that UK trees have succumbed to many devastating problems. One of the first to be widely recognised was Dutch elm disease, which was said to have been accidentally imported from
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