Diarmuid Gavin: Hedge your bets
Get your evergreens in shape this month before the first frosts arrive
Now that September is upon us, it's a great time to give your evergreen hedges a final trim for the year. This way, you will have a fresh-looking but tidy hedge through the autumn and winter.
Cutting now allows time for plants to harden off - there's still a little warmth in the soil to allow for some new growth, and temperatures should slowly cool, allowing your plants to adjust without too much of a shock. So whether it's a privet, box, Leyland cypress, holly, laurel, yew, viburnum, thuja or Lawson's cypress that you need to tackle, here's my handy guide.
What equipment do you need? A hand-held shears, if sufficiently sharp, will be fine for smaller jobs. These are implements which are easy to have good control over, and would be my preferred option for jobs that require precision, such as clipping box balls. However, bigger stretches of hedging will benefit from some power tools. Safety with power tools in a garden must always come first, so if you are using an electric hedge trimmer, always use an RCD - this is a circuit breaker that will automatically disconnect the electricity if you accidentally cut through the cable. This, unfortunately, is a more common occurrence than you may think.
A safer option is a battery-operated cordless device: these are lightweight and, with lithium batteries, can keep going long enough to get the job done. There are also petrol-operated trimmers but these tend to be a bit heavier. And put a tarp or bit of plastic down to collect the clippings, which can go straight to the compost heap afterwards.
Next, what shape do you want to achieve? A wedge shape or flat-topped A-shape is best for hedges - in other words, you want the base to be a bit wider than the top, so it should taper slowly inwards. This is also known as putting a 'batter' on a hedge. The reason for this is to allow sunlight to get to the lower part of the hedge. If the base of the hedge is being shaded by a wider top, it tends to get bare-stemmed. 'Battered' hedges are also less likely to suffer snow damage.
Of course you may not want a flat top and prefer a dome shape. This is trickier to manage, but a cardboard template of the shape you like is a good way to achieve this, moving the template along the top of the hedge as you proceed.
Height is another consideration. There are regulations when a solid evergreen hedge climbs over two metres, as this can cause light- or view deprivation to your neighbour, so keep this in mind.
If you share a boundary hedge with a neighbour, both of you are responsible for its upkeep, but you aren't allowed to clip any part of the hedge that falls on your neighbour's side without permission. If a neighbour's hedge is overhanging into your garden, you're entitled to remove any branches that stray into your boundary.
Be careful when trimming conifers that you don't cut back into old wood: they don't rejuvenate from old wood and you'll be left with bare patches. Yews are the exception to this rule - they can be cut back hard if you deem it necessary, but such a hard prune would be better done in spring.
If you're growing a conifer hedge and it hasn't achieved the desired height, don't cut the leader shoots at the top yet as this will stifle growth; just clip the side of the hedge. When clipping cherry laurel (Prunus laurocerasus), you might notice that, because it has large leaves, some of these get cut in half. It's a good idea to go over the hedge with a secateurs and remove these, as they will develop a black margin that spoils the look of a hedge. Don't be tempted to feed hedges now - new fresh growth encouraged by nitrogen-rich fertilisers can be burnt in early frosts.
And, finally, remember the birds. For them a hedge can be a home, a nesting place. The Royal Society for the Protection of Birds recommends leaving hedges alone from March to August, which is the main nesting season, but it is an offence at any time of the year to intentionally destroy the nest of any wild bird while it is in use.
It's always a good idea to wear protective clothing and even basic safety equipment for hands, ears and eyes. Never have loose bits of fabric, such as sleeves or even rope-type ties from hoodies, flapping about. These can get caught and pull you towards moving equipment, resulting in injury or worse.