Cherry laurels are grown for a number of different reasons and purposes, but basically the pruning regime insofar as timing is concerned is the same for all. The main difference of how to prune laurels depends upon the variety and the habit of growth.
Some Laurels are grown as ground cover plants. Others are grown as , large shrubs, hedges or screens. As with all evergreen shrubs , they are best pruned in the growing season. If you want the added feature of flowers, then timing is quite important.
If you prune laurels in early spring or even in late autumn/winter, then you will probably prune off the flower buds, and I therefore not have the quite spectacular show of creamy white flowers which as an added attraction to the main purpose the laurel is grown for.
The two main varieties of Prunus laurocerasus, grown for their low spreading habit, are Prunus laurocerasus 'Otto Luyken' and Prunus laurocerasus 'Zabeliana'. As they are normally grown as ground covering shrubs, pruning is mostly not required. However, both have a habit of outgrowing their original location or allotted space as they mature.
For all varieties of Cherry Laurels, the best time for pruning to ensure flowers is immediately after the flowers have faded. If your main concern is to have the Laurel as an evergreen screen or ground cover, then pruning can take place at any time up until late summer. Later pruning is possible, but the late new growth as a result of late pruning can be subject to winter damage - often as unsightly blackened foliage.
Laurels of all types are actually members of the large Prunus or Flowering Cherry Family
To keep them in check - both for height and spread - drastic annual pruning may be required. It is far better to cut back the individual branches quite hard with a lopper - rather than being too fussy with hedge clippers. This is best carried out after flowering, of at any time during the summer. They can also be cut back in winter. (See below for hard pruning).
The spreading habit is best maintained by pruning the height as well as spread. Otherwise they will tend to grow taller than their desirable height of up to 1 meter (3 feet).
With hedge and screening Laurels - Prunus laurocerasus Rotundifolia and similar large leaved varieties, the matter of flowering is a secondary consideration. It is the screening effect of the dense foliage which is the desirable factor. When to prune Laurel hedges is largely a matter of fitting in with your own routine, or where untidiness of the hedge warrants attention.
It is often written that pruning of laurel hedges should be done with secateurs rather than hedge clippers. I myself – and the laurel hedge – have always been happy with the use of electric hedge trimmers. This is particularly the case with large hedges. True some of the leaves will be cut in half, but with no lasting harm or visual disfigurement.
If it is a solitary screening laurel, then use secateurs if you must!
The main consideration regarding when to prune laurels hedges, is the state of the seasonal growth. Late august seems always to be the best time to clip, for there is then time for the hedge to re-grow a covering screen for the winter months.
Just do it!
Laurels can be cut back as hard as you like from early spring through until late summer (late August). If after that time, then the best time to cut back hard in late winter. The new growth will soon start to shoot out as soon as the spring warmth begins.
I have cut back huge laurels – some several metres tall - in mid winter, and the rejuvenation effect soon takes place, with rapid new growth wanting to get back to original size as soon as possible!