Trim your hedge regularly
Hedges only look beautiful and neat if pruned regularly. Neglected, any hedge will have a tendency to spread out and become bare inside.
It is necessary to differentiate between an adult hedge and a growing hedge. For an adult hedge, we are talking about maintenance pruning. For a growing hedge, we are talking about formative pruning done until the plants have achieved their adult height and size. It should encourage the development of lateral branches and prevent bareness at the base; this should be carried out from the very first year.
For informal hedges, the only tool that should be used is pruning shears to allow the irregular shapes and forms. Cut off the inside dead wood, avoiding to create holes in the process. Before each cut, carefully select what you are about to cut.
For formal hedges, do not cut at random, use a piece of string or metal (more resistant if touched accidentally) between wooden posts planted in the soil as guidance. The line should be perfectly horizontal (use a spirit level if necessary). Then you can proceed, following the line with your hedge trimmer.
Regularly prune young plants to encourage new growths
Formative pruning for regular hedges:
During the year of plantation and the first few years, roughly level out the outside faces of your hedge. The base needs to be slightly larger than the top to allow all the branches to benefit from the sun. For the broad- leaved hedges, take out 30 to 40 % of the current year growth, repeating the process until the final desired height and spread are obtained. The tops of the conifers are only cut off when the desired height is finally obtained. Until then, only the lateral branches are pruned.
In a few years, when your hedge has reached its definitive adult size, you will only have to do annual maintenance pruning to keep it looking beautiful.
When to prune your hedges:
The time for pruning flowering hedges is the same as for the single flowering shrub, meaning after the blossom has appeared.
The time for pruning your formal and screening hedges depends of the composing shrubs in the hedge.
For broad-leaved plants, prune in the spring (April) then end of September.
For conifers, prune in June to benefit from the freshness of the springtime growth. Do not prune after September, as the cuts will heal badly.
Be careful about using electric trimmers; their speed of cutting can sometimes cause unfortunate mistakes, which are difficult to conceal or rectify, especially for inexperienced gardeners. Take your time, be patient or use manual pruning shears that do have the advantage of cutting off one branch at the time.