Appendix on native plants
Appendix on native plants
This forms part of our management policies for LWA.
Plants in Britain can be classified as native, naturalized, alien or cultivated. There are around 35 species of native tree, for example, depending on how certain sub-species are counted. These plants were already here or arrived here naturally - that is, without Man's help - after the last Ice Age, about 11,000 years ago. Britain was still part of mainland Europe and plant species slowly moved north-west into it as the climate improved and the ice retreated northwards. (There were only about 200 species here at end of the Ice Age.)
With the gradual warming of the world's surface, the ice began to melt, raising the seas. Eventually, about 8,000 years ago, the English Channel flooded. This stopped the natural migration of plants from the rest of Europe, one consequence of which is that we have only about half as many native species as France, for instance. (Scientists know this from pollen deposits and fossil remains.) This date is taken as the cut-off point for deciding whether a plant species in native or not. Examples of native trees on the reserve are Ash, English Oak and Field Maple.
Naturalized species are introductions. They are native somewhere else but arrived in the British Isles more recently than 8,000 years ago, being brought deliberately or by accident. Their seeds were perhaps carried in with imported goods or were caught in people's clothing. Plants that are naturalized can reproduce unaided in Britain. Both species of Chestnut in Centenary Fields are examples.
Exotic species are also recent introductions. These too are native somewhere else but cannot reproduce unaided in Britain. Black and White Walnut are exotics, for instance.
Cultivated species (`cultivars') are, by contrast, native nowhere. Man has guided their evolution, typically by deliberately cross-pollinating between species or varieties. (This is true of almost all crops and garden plants.) The Acer pseudoplatanus `Leopoldii' in Centenary Fields is a cultivated species (a `cultivar').
Some trees are native to only certain parts of Britain. The Scots Pine, as its name suggests, is native only in parts of Scotland. Beech and Hornbeam are native only in south-eastern England. Outside these areas these species are technically regarded as introductions. In other words, in some parts of Britain these are naturalized species.
Using native plants
Native plant species support more, and more diverse, communities of other life forms than do introduced or cultivated species. They provide food, home and shelter - above and below ground or water - to a wide range of microbes, algae, fungi, lichens, other plants, invertebrates, amphibians, reptiles, birds and mammals. For example, the two native Oak species (Common and Pedunculate) play host to nearly 500 species of invertebrate, another 40 or so that cause galls and over 300 species of lichen.
Compare this with Sycamore. It is an introduced species, arriving here in the 13th century. Despite that long residency, only 43 species of invertebrate feed on it and only 8 gall causers exploit it (it does, though, host a remarkable 183 species of lichen.)
The ability to sustain such communities comes about mainly with time. So long as climatic and environmental conditions are suitable, the number and range of species that a plant can sustain will increase the longer it is in an area. This applies locally as well as nationally, which is why it is preferable to plant specimens that grew reasonably close to their destination. The species and communities that an Oak tree in Durham supports will differ from those on an Oak in Devon.
The complexity of these relationships is sometimes bewilderingly intricate. The caterpillars of several gall wasps, themselves parasitical on a host plant, are parasitised and preyed on by other invertebrates, both within the gall and outside it. Up to 20 different species have been identified as interacting in a food web around some Willow and Oak gall causers. Such a complex set of threats and dependencies take hundreds upon thousands of generations to become established. Even at insect breeding rates, that cannot happen in just a few hundred years.
Origins [not part of the agreement]
Any plant or seed we plant must therefore has to have originated locally or in the UK, not merely come from a local or UK plantation or nursery (which is its provenance). A Sweet Chestnut whip from an East Grinstead nursery, for instance, would have local provenance but not be of UK origin, since this is an introduced species.
The Forestry Commission publishes a useful paper on this topic as it applies to trees. This also gives a good introduction to planting zone system (LWA is in zone 405). Entitled Using Local Stock for Planting Native Trees and Shrubs, it is numbered FCPN8. It can be ordered in paper form from the Commission or downloaded as an Adobe Acrobat file from here.
Further advice, applicable to a wider range of plant species, can be found on the Flora Locale Web site.
A different and interesting approach is that of The Natural History Museum's fPostcode Plants Database. This draws on historical data to say what has been found in various parts of the country. Here is the entry for "RH7", the postcode for Lingfield; it may take a while to load. The site also lists British native plants, butterflies, birds and mammals.
The Herbiseed company has this page, "Wildflower Species for Particular Habitats", which gives planting suggestions for varied soil types.