The previous owners of our property planted a hawthorn hedge as screening from the road but it's clearly not been managed for severally years; they're now established trees 10+ feet tall.
Hawthorn is known to be resilient to pruning but does this ever get lost as it grows? If I radically prune my trees how will they respond?
The resilience of hawthorn is maintained as it grows; unlike softer members of the same family even smaller twigs are quite tough and wiry. All plants are somewhat softer at the tops compared to lower down but hawthorn maintains its toughness. It is for this reason it has been used for fencing cattle, as layered hedges. About the only thing that could penetrate it was a tank or a digger/backhoe.
The hawthorn will survive radical pruning and quite brutal treatment but of course will lose its shape and attractiveness if done without regard for consequences. I guess the important thing is to decide what function it is supposed to perform - if a thick hedge then make sure that there is sufficient growth at the base to make it a solid wall. Thorn hedges are distinctly more attractive if green right to ground level; bare trunks, while extremely solid and capable of resisting a bus in full flight, won't keep out rabbits or rubbish.
The best way to rejuvenate a really overgrown hawthorn hedge is by "laying" it. This can be done any time of year but was traditionally done on farms in winter, when there was not so much other work to do. It is easier when there are no leaves on the hedge, and these days it is illegal to do any commercial hedge trimming work during the bird nesting season.
The basic tool is a chopper (not a saw). In my part of the UK they were called "billhooks" because there the blade had a curved end, which was handy for pulling branches into position.
Prune off any long branches to leave a hedge about 6 feet tall. At this stage it will probably look a complete mess, with big holes between the separate plants at ground level, but don't worry about that.
Then, chop through about 75% to 90% of the main stem of each plant close to ground level, and bend the top part down almost horizontal. The top part is held in place with stakes, and by "weaving" some of the long pruned branches into it. You want to end up with a hedge about 3 feet tall where almost everything is close to horizontal, not vertical.
A chopper is a better tool than a saw, because it naturally follows the grain the wood to produce a cut that will bend through 90 degrees without breaking.
So long as you leave some bark and sapwood intact when you chop into the branches, everything will re-grow. During the first year, cut out any long growths that are heading in the wrong direction, e.g growing sideways out of the hedge, or getting too tall. By the second year you will have a solid hedge that you can keep in shape with a trimmer.
Warning, this is hard work. If you are a beginner, laying about 5 to 10 yards of hedge in a full day's work will be good progress.
