"Renewable resource" is a phrase we're constantly hearing, often in a context that's supposed to make us believe it's a freshly-minted idea. Of course, it's not. Gardeners have always understood the concept.
Coppicing, for instance, exploits the fact that some shrubs and trees, when cut hard back, won't give up the ghost, but will produce strong, vigorous thickets of new growth, renewing themselves time after time.
Round where we live, there are still masses of old hazel coppices, though no one cuts them any more and the stems, springing from big, old boles, have become very thick. But as well as firewood and charcoal, hazel once provided spars for thatching, twigs for dowsing, wattle for hurdles (masses of those needed in the sheep folds) and the foundation for wattle and daub, the woven partitions covered in mud and horse hair used for a cottage's inside walls.
Round Petworth, the coppices I knew were mostly sweet chestnut, cut, split and used for fence posts. It doesn't need treating and lasts much longer than softwood rubbish. Those coppices were still being well-managed when I used to haul small children through them, one block cut down each winter in a 12-year rotation. As soon as light reached the understorey of the cleared blocks, it sprang into growth again: primroses, wild daffodils, bluebells, anemones.
In our gardens, we can use coppicing, not just to restrict the size of a potentially large tree or shrub, but as a way of persuading them to give us a particular effect – more brilliantly coloured bark perhaps, or a different kind of leaf. And there are plentyf of ways we can use the trimmings. Both hazel and birch provide fine, twiggy growth ideal for staking. Bigger lengths of hazel provide pea sticks and bean poles. The coloured stems of dogwood can be woven into the kind of lobster pot plant supports that you always mean to make. One day.
Although you rarely see it suggested as a tree for town gardens, hazel has a lot to recommend it. Of course, now is perhaps its best season, the older growths hung with catkins, fat and yellow with pollen. If it wasn't so common, so easy, we'd be going into raptures about it. It's eminently manageable. The leaves often turn a good, clear yellow in autumn. It makes a pleasing winter silhouette. And it provides food. Except that the squirrels are bound to get the nuts before you do.
But if I had an eyesore at the bottom of a town garden I wanted to screen, a row of hazels would not be a bad choice. Better than a solid barrier, which can make a smallish garden feel too enclosed, too prison-like. The canopy will please any local birds that still dare run the cat gauntlet. And if you coppice regularly, you can keep the trees just the size you want.
Now's the time to do it. But you need the right tools, a handy small saw and some sharp secateurs. Loppers aren't the best things to use on the thickish stems you'll be cutting out. They squeeze and bruise before they cut, inviting disease into the damaged wood. A saw cut is cleaner.
Hazel can be bought very cheaply as one-year old whips. You need to get the plant well-established before coppicing can start. But after three years, say, you should have a strong, probably single-stemmed plant. Then, round about this time of year, you can cut that stem down to the ground and during the following year, the 'stool' will sprout three or four new stems. I'd then let those grow on until at least one of them started bearing catkins.
Then I'd start on a rotation, cutting out just one of the thickest and oldest stems in the clump each year until the whole thing was as big and bushy as I wanted. After that, you can start taking out rather more stems.
Hazel is very forgiving. So is hornbeam (Carpinus betulus), which you can treat in just the same way. And both grow quite quickly, which if you are coppicing them, is an advantage. With your own supply of hazel to cut, you need never buy an imported bamboo cane again.
Dogwoods are regularly coppiced because the coloured stems (the main reason to have them in the garden) are brightest when they are young. When you buy a dogwood, it will probably already have a framework of several branches. But you need to leave it alone for a couple of years before you start coppicing. That way, it'll have time to grow a decent network of roots. If it doesn't have sufficient roots, it won't be strong enough to produce all the new shoots you want.
Cut dogwoods back in early spring. Gardeners are often told to cut the whole clump down at once. I think it's better to take out a proportion of stems each year – say a third. That way, you don't lose the whole bulk of the shrub, which may be important in the planting, and you don't put such a strain on the shrub itself.
You'll still give it enough of a jolt to produce new growth and the bright colours that shine out so well during winter. My favourite is Cornus alba 'Elegantissima', although its red stems are not as brilliant as 'Sibirica'. But 'Elegantissima' has variegated foliage, good for picking. And if you don't cut it down altogether, you'll get some stems old enough to produce flat white heads of flower, very light and pretty with the leaves.
Any dogwood that you grow for its winter bark can be treated in the same way. But bear in mind that the showy variety, 'Midwinter Fire', is not always as vigorous as other kinds such as acid-green 'Flaviramea' or black-purple 'Kesselringii'.
Willows, too, can get the same treatment, though they grow more strongly and you will probably need to cut out more growth each year than you do with dogwoods. Salix alba var. vitellina 'Britzensis' is a male clone that produces bright orange-red shots. Salix irrorata has mauve stems with a whitish bloom.
In a small garden, though, it may be better to manage a willow as a pollard, so you can use the space round the trunk for other plants. The technique is much the same. You just let one trunk grow up to 90-200cm (3-6ft) before making the initial cut. Then you work with the shoots that are produced from the head at the top of the trunk.