When you first plant hawthorn, trim the main stem by a third to a half to encourage branching lower down.

For routine trimming, the timing is all about how the hedge responds. Too early and you'll have to trim again and again. Too late and re-growth could be killed.

Of course, if you want a razor-sharp hedge, you'll have to trim little and often. And if you don't want to deal with a heap of very thorny woody trimmings all at once, then frequent trimming of the soft new growth makes handling hawthorn much easier.

Initial pruning

Except for conifers, prune out leading growths on planting, to encourage lots of side shoots from the base of each plant.

Regular trimming

To encourage growth down to ground level, make sure the sides of the hedge are vertical or slope inwards towards the top, producing an A-shape profile. Then upper growth will not shade out lower growth.

If using a powered hedgetrimmer, sweep the cutter blade upwards. If you cut downwards you'll pull branches out of line and end up with gaps in the side of the hedge.

Overgrown hedges

You can cut deciduous hedges hard, almost to ground level, where they will put out new shoots about a month later - once the plants have recovered from the shock. Cut back in late spring so that new shoots will not emerge when there are still frosts or cold winds around to damage them, and so the shoots have time to ripen before cold weather returns.

Unfortunately conifers do not respond in the same way, and if you've ever cut into a conifer you'll know that the greenery is all on the outside. Cut too much off the top or sides and you'll end up with unsightly dead patches. The best solution is to grub out the whole hedge, but if you plan to plant another, you'll need to dig in plenty of compost to build up the soil.