Although not often necessary, yew trees have a great ability to produce fresh growth from very old wood, and an irregular hedge, or one of the wrong height or width, can be trimmed back to a desired size or shape. Such drastic pruning may best be done in the spring but the normal regular clipping is a task for July and early August. Well maintained a yew hedge, with its dull surface, is the ideal foil for borders or flower beds or as screens for walks or formal lawns where privacy is desired. It is also the ideal plant for the most intricate topiary. Quite tall plants can be used to produce a hedge in a short time but it is cheaper and almost as quick to plant young plants of about ift(30cm) in height at from 1J to 2ft(45 to 60cm) apart. x Cupressocyparis leylandii, the Leyland cypress, was first found growing as a natural seedling almost one hundred years ago. The seed was from Chamaecyparis nootkatensis that had been pollinated by Cupressus macrocarpa. In recent years the cross has been deliberately repeated and several distinct clones have been selected. Being propagated vegetatively each batch of plants should be uniform in vigour and appearance. It makes rapid top growth that is not always balanced by equally vigorous root growth unless planted very young. For the best results Leyland cypress should be planted as newly rooted cuttings as this allows a good root system to be produced before the aerial growth and with it a fair chance that the plants will remain upright in all but the most exposed conditions. It is very frost-hardy and withstands all but the most severe coastal gales. This hybrid withstands trimming far better than either parent; it bears some comparison with the yew and reaches a satisfactory height more rapidly. Unless the base is left wider than the top or is otherwise exposed to full light the lowest branches will die off and will not be replaced. 'Castlewellan', a cultivar with golden foliage, can be made into an attractive hedge for the right situation where a light rather than a dark background is needed. Chamaecyparis lawsoniana, the Lawson cypress, is one of the best known of all conifers. The many forms of this erect-growing conifer make useful untrimmed screens but as clipped hedges can bring certain problems. All reach a considerable height in due course but some, such as certain golden forms, do so less rapidly. The tops of each plant may be removed to restrict upward growth and preserve a limited hedge for several years, but they are all better as untrimmed rather than formal hedges. All have a tendency to become thin at the bottom, and they then need low shrubs in front of them to hide their ugliness while allowing the upper branches to screen unwanted views or provide a background or shelter from wind. Cupressus macrocarpa, the Monterey cypress, is even less tolerant of trimming than other conifers and more likely to lose its bottom branches.