Tree planting for forestry and wildlife has had a much shorter history than tree planting for fruit, shelter and pleasure. The earliest civilisations are partly defined by their ability to grow crops and plant trees in gardens and orchards. From the Garden of Eden onwards, there has been an urge to collect and plant useful and beautiful species of tree.
The Romans introduced the sweet chestnut, the cultivated apple, the medlar and other species to Britain. The temperate climate of the British Isles allows a huge variety of trees and shrubs from all over the world to be grown, and introduced species have provided a great impetus to gardening and the growing of trees. Our gardens, parks and streetscapes are characterised by the introduced species which they contain.
Most of our native ‘forest’ trees, such as ash, beech, lime and oak are too big or cast too dense a shade to be grown as garden trees. The smaller native trees such as rowan, crab-apple, hawthorn, holly and yew have been widely planted in gardens, parks, roadsides and churchyards, and many different cultivars have been identified and propagated for their particular foliage, fruit, flowers or form of growth.
Trees which are planted for mainly ornamental reasons also have important environmental benefits. Although native trees support the highest number of invertebrates, many introduced trees are also valuable for invertebrates, and may be of equal value for birds and some other organisms. This is because trees in urban areas, whether they are native or introduced, tend to support a range of generally common, though valuable, organisms. It is only the very ancient veteran native trees in parks and wood pastures, or the community of trees in the specialist, humid environment of a woodland where native trees have their highest ecological value. Introduced or native trees are equally valuable for reducing greenhouse gases, counteracting the heat-island effect of towns, reducing noise, filtering pollutants and making people feel better. In urban areas, introduced trees are certainly better than no trees at all.
Trees in towns and cities have much to cope with, including low humidity, high reflection from paved surfaces, air pollution, disturbed ground and poor drainage. Urban areas have higher temperatures and much lower humidity than surrounding rural areas, with conditions in some cities approaching those of the Mediterranean. Our native woodland trees are adapted to humid air, shelter and shade, and may not thrive in urban conditions. Introduced species or hybrids often have better resistance to drought, dry air, pollution and wind damage than native species, and as such are better suited to growing in towns and cities.
Introduced species greatly lengthen the season of flowering and fruiting, so that for birds, invertebrates and other organisms there is a greater range of food available throughout the year. Urban beekeepers consistently produce higher yields than rural beekeepers, because of the range of nectar available from introduced plants in parks and gardens, and because of the higher air temperatures. Many species of birds also thrive in the woodland-edge type habitat of the leafy suburbs.
Choosing and planting introduced trees
There is a huge range of trees available from garden centres, nurseries and specialist suppliers. Choice should be made according to the soil type, situation, space available and the purpose of the planting. There are many books available in libraries and bookshops which can be consulted for further advice, including the following:
The Tree and Shrub Expert
Dr D G Hessayon (pbi Publications)
The Royal Horticultural Society (Dorling Kindersley)
The Hillier Manual of Trees and Shrubs
Hillier (pocket edition also available).
Introduced trees are normally not available as small, two year, bare-root transplants, but are grown in the nursery for another year or two until they are 1.2-1.8m (4-6ft) in height. Some species also benefit from early pruning, which is best done in the nursery, to form a balanced head of growth. They are sold as either bare-root, root-balled (wrapped) or container-grown plants, depending on the species and the supplier. Garden centres normally sell container-grown plants. With ornamental trees, many purchasers want to plant for immediate impact, and at any time of year, and are willing to pay the much higher prices which older, container-grown stock commands. As with any tree, the shock from transplanting and the generally poor root:shoot ratio of standard trees means that such trees may be slow to establish and put on new growth. Choosing the smaller, younger and cheaper sizes available for any species will, given correct care, lead to the best establishment. Even for container-grown stock, planting in autumn is the best time of year.
When planting, follow the advice given here for pit planting. Tree roots spread and are mainly active in the top 60 cm (2’) of soil, so generally dig a hole which is wider than it is deep. A hole 1m (3ft) square is not too large, and should be backfilled with a mixture of soil and compost. This forms a graded zone between the compost in the container and the surrounding soil, and encourages new roots to venture out of the compost and into the new ground. A circle of at least 1m (3ft) diameter around the tree must be kept free of grass for at least 3 years after planting.
In the past, most farms and gardens, large and small, included an orchard of fruit trees. Before the days of cold storage and rapid transport, fruit was mainly limited to the types you could grow in your own locality. In Britain, as in other countries, hundreds of local fruit varieties were cultivated and identified, with areas having their own particular apples, pears, plums and other types of tree fruit.
Most private gardens have at least one fruit tree, but with cheap imports of fruit, private and commercial orchards have declined rapidly in recent decades. Many have been grubbed out and converted to agricultural use or building development. The charity Common Ground is active in promoting the saving of old orchards and the planting of new ones for community use. Common Ground publishes a series of Orchards Advice Notes, a newsletter Orchards News, and provides a useful forum for all those interested in community orchards. The Brogdale Horticultural Trust in Kent comprises the National Fruit Collection, including the largest collection of apple varieties in the world. It offers training events, a fruit identification service and supplies a wide variety of fruit trees.
Fruit trees are available from garden centres and specialist nurseries, and many books are available on their cultivation and care. Fruit trees are grown on rootstocks which affect the growth and fruiting potential of the tree, with dwarfing rootstocks recommended for smaller gardens. For large gardens and orchards, standard or half-standard trees on semi-dwarfing rootstocks may be suitable. The Fruit Expert by Dr D G Hessayon (pbi Publications) gives clear details on the growing of tree and soft fruit.
One-year-old maiden trees, available bare-root from specialist suppliers, are the cheapest way to buy, but will require careful pruning for at least three years to form a balanced framework of branches. Two-year-old, partly trained trees are usually the best choice. Trees over four years old should be avoided, as they will be slow to establish.
Planting should follow standard advice. Staking is normally necessary at planting, and may need to be permanent for small bush trees. Trained trees, such as espaliers, will need appropriate supports. For the best crops, the ground under the fruit tree should be kept clear of other growth, especially grass. For orchards, bare ground is normally only appropriate for commercial growing, and most community orchards will include grasses and wild flowers. Fruit trees are prone to a variety of pests and diseases, and attention needs to be paid to their cultivation and care.