Pruning Trees and Shrubs in Early Summer
The major part of pruning in early summer is taken up with the late-spring-flowering shrubs and some of those flowering early in this season. It may also be necessary to finish off the pruning of the mid-spring bloomers, if they were late flowering because of the weather or an exposed site. Shrubs to prune now are given in the following list.
Broom (Cytisus and Genista)
Cytisus scoparius and its varieties are shrubs which really need annual priming, otherwise they get very leggy and sparsely flowered. The flowered sprays should be cut to leave about 2.5cm (1in) of their previous summer’s growth; always leave this and do not cut into older growth. Other cytisus species and varieties can also be pruned if flowering has finished, being careful not to prune old wood or unbalance their natural shape.
Most genistas do not need pruning except for the Mount Etna broom (G. aetnensis) and one or two others in late summer, and the Spanish gorse (G. hispanica) which benefits from a light trim all over with shears after flowering. On the whole, genistas have a tendency to flower themselves to death and there is no need to encourage flowering — rather discourage it.
As soon as flowering has finished, the sideshoots on a specimen grown against a wall should be cut back hard, to leave only a few centimetres (1 or 2 inches) of stem. Weak shoots should be removed altogether. Plants growing in the open need not be cut back so hard but if you cut some of the sideshoots by about half the bushes will be denser and thekinds, in particular, will be less vulnerable to cold.
Some of the alpina and montana types may have continued to flower until the end of late spring, so will need dealing with at the beginning of this season. However, it does no great harm if you leave them alone, and C. alpina will then produce attractive, fluffy seed-heads, like a cultivated form of old man’s beard.
An easy shrub to prune, as the new growth will be very obvious by now. The flowered shoots at the base should be cleared out and weak shoots removed unless they fill a gap, when they can be left until next spring.
If you did not prune it hard in mid-spring and intend trimming it through the growing season, you can give it the first trim with shears now; the object is to make it bushier and better covered in its silver-grey filigree foliage.
Pruning is not necessary except occasionally, and then only to cut one or two of the oldest stems out completely; tips of shoots infected withshould be removed as soon as seen.
The species S. van houttei will need its flowered shoots removing at the end of the season, down to where strong new shoots are already growing. The same technique can be applied to S. x arguta if not pruned in late spring.
Tamarisk (Tamarix tetrandra)
Prune early this season.