Webmother's note:
The late Alan Mitchell was one of the
most knowledgeable foresters this country has possessed recently. He was
also very outspoken and passionate in his views. Alan was the author of the
highly esteemed reference book "A Field Guide to the Trees of
Britain and Northern Europe". He also wrote many other books and
articles and worked for the Forestry Commmission before he retired. Amongst
many other things he was the Director of TROBI (Tree Register of the British
Isles).
The small article below from "The Tree Book" makes a
great contribution to the Reforesting Britain debate on this
website. It sums up the case for supplementing our long-time native
trees with a wealth of other trees from all over the globe.
I like a tree to get on with it — it has to be vigorous, because it’s got to get big or it goes on the bonfire — or else it has to be very pretty — otherwise I wouldn’t bother to find room for it in the first place. I like good foliage and interesting flowers — a tree has got to have character.
A half-serious rejoinder to the question ‘Why would you plant exotic trees?’ is ‘Because there is no point in planting natives — they plant themselves.’ The gales of the last four years have shown how efficiently native trees replace themselves. Country-wide, all native species —except the wild service tree and the black poplar — seed themselves adequately and none is in need of the ‘conservation’ which is now mindlessly attached to everything growing. Jays plant hundreds of millions of oak trees every mast-year — most of them, it seems in my garden-beds — yet I am begged every so often to go and save an oak seedling from eradication, ‘since they are now so rare’. A hundred thousand seedlings of Scots pines are removed from Frensham Common each year in the National Trust and Surrey Trust ‘Pine-Pulls’ designed to save the heathland for snakes and natterjack toads. Except locally, sometimes, native trees are in little need of being planted.
There are, however, even more cogent reasons for planting exotics than this negative one. One is that few exotic trees plant themselves, so if we value their ‘conservation’ here, we must plant them. One obvious exception is the sycamore. Less obvious and very local are the natural seedlings of western hemlock, western red cedar, Lawson cypress, Norway maple, and sweet chestnut, with far fewer Monterey, maritime and eastern white pines, red oak, silver fir and a few others. If we want the noble spires of giant sequoias and grand firs to tower out of the monotonous domed tops of so much of our woodland, the delights of walking in larch woods, and of monumental cedars of Lebanon to grace our towns and parks, we must plant them.
Another reason is that replacing woods by natural seeding, or by planting the same native species, is a very conservative approach which can add nothing to the variety of species and, usually, very little to the quality. We have only about 35 native trees, a minority of which can grow to great size, and only four of those are strictly native to all regions, the others being confined to England or to Scotland. Furthermore, with only 35 species, we are exceedingly unlikely to have among them the best ones we could have for growth, amenity or any special requirements, on all kinds of soils and sites. For example, no native tree can thrive like the sycamore, giving shelter in extreme maritime exposure on limestone soils at over 300m (1,000ft) and none can withstand that exposure on sands at low levels like the bishop pine from California.
Nor is any attractive native tree particularly well suited to city life. Our trees are nearly all forest-edge species, needing woodland soils and clear air, a cool temperature and high humidity. For paved root-runs, heat reflected from buildings and drying winds of polluted air, we need gingko, robinia, planes, honey-locusts and others selected from all over the world.
Our native trees are singularly devoid of attractive flowers. If they are big trees, they bear catkins or insignificant flowers; only small ones like the rowan have noticeable flowers — with the exception of the great display of the wild cherry. The horse chestnuts, catalpas, spectacular cherries and apples — invaluable in street parks and gardens — are all exotics. Another drawback to natives is that they bring all their pests and diseases with them from the woods. Who wants a garden or street tree with leaves tattered and blighted, if a range of shiny-leafed, healthy, insect-free exotics is available?
A garden is a planting designed to be distinct from its background, not to merge into it, and to be decorative. In a wooded countryside it can do this only by being formed of different (and superior) tree species. In effect, this is saying that it must be planted largely with exotics. The world’s great gardens are all collections of trees exotic to the country of the garden. Westonbirt, Sheffield Park, Powerscourt, Leonardslee, Longwood, Winterthur ... they all owe everything to exotics, and so do millions of very much smaller gardens.
A panoramic landscape in Britain is a monotony of rolling, formless tree crowns, and is visually uninteresting without a lake or mountain. In lowlands, where these are absent, it depends on church spires or a good clutch of cooling towers for the eye to rest on, to distance the elements and to which to return. In most areas, however, this essential ingredient can he found in the planting of giant sequoia or a Lombardy poplar or two and clumps of big Douglas firs and mixed conifers in an estate or even a garden.
Our birds need exotics in gardens and forests. Almost no native tree other than yew has a leaf to hide a nest in March and April, when they are most needed. The Lawson cypress from California, universal in gardens and churchyards, and now the Leyland cypress, are the sites for most of the garden bird nests in town and country; the western hemlock and Douglas fir in forests built up the high populations we now enjoy of goldcrests and redpolls, while the sitka spruces, in the forests of Dumfriesshire, restocked the locally extinct sparrow-hawk in its recovery to former numbers everywhere. A recently added bonus of exotic trees is the now thriving colonies of breeding golden orioles in Suffolk. They nest exclusively in the hybrid Robusta poplar and, until a decade or two ago, a single nest was a great rarity.
The vagaries of geology, in the forms of northward continental drift and ice ages, have deprived Britain of all but an outlying fragment of an impoverished North European flora. It may be nice to preserve some areas for that flora alone, but as a general policy of planting for many purposes, it is perverse to restrict ourselves to these few trees. The wealth of the world’s flora is available to us.
A great number of splendid trees grow better here than they do in their native areas — a general rule in exotic plants — and our basic 35 species can be augmented to 2,500 at least. Is it not common sense to exploit fully our remarkably benign climate and grow the plants which have and still are being introduced from other countries by man to make our gardens the envy of the world and so enrich our towns, cities, villages and countryside?
From: Milner, J.Edward - "The Tree Book, the indispensable guide to tree facts, crafts and lore", Collins & Brown Ltd, 1992
