Who of you out there has a fast growing Leylandii hedge (golden or green)? Maybe you call it by its Latin name x Cupressocyparis Leylandii or maybe you call it that damned high maintenance, sunlight blocking hedging. Please try not to be so hard on this conifer, as evergreen hedges with thick foliage such as Leylandii, can filter out up to 30% of atmospheric pollution. Now, I have called it a hedge but maybe I should have called it a line of trees, because your Leylandii is in fact a tree not a hedging shrub. You will have realised this, if you have been fighting a losing battle to keep a Leylandii hedge to a height that will still allow sunlight to enter your property.

When to prune, side and top

This crazy growth conifer tree is always trying to get to its ultimate height of 20 metres (60 ft) and ultimate spread of 5 metres (15 ft). So for most people this means pruning their hedge religiously each year, missing a years pruning will result in excessive labour at dangerous height the following year. Anytime during the month of May is a good time to trim and tidy up a formal Leylandii hedge. Many people choose to trim in late autumn when giving the garden a late tidy, I would always avoid this. The reason being that if you leave a buffer of straggly growth over winter this will offer protection against frosty or cold wind damage, any browned or burnt foliage can be trimmed off during the month of May. If you had trimmed in late autumn and subsequently received some cold wind damage, you would now have to trim a second time, leaving a rather bare and see through hedge.

How often and how hard can I prune?

Ideally, you should trim a formal Leylandii hedge every season trimming no deeper than 15 cm or 6 inches on each side, this will encourage the hedge to fill out and thicken. Beware, trimming or should I say cutting back into older wood on Leylandiis is best avoided. This is because most conifers including Junipers, Chamaecyparis and Yew will not grow new shoots or leaves on old wood. You will see examples of this exhibited on the many brown patched Leylandiis that litter our countryside and towns.

Leylandii and the law

In Britain, x Cupressocyparis Leylandii is estimated to be the cause of over 20,000 ongoing neighbour disputes. The disputes usually centre on encroachment or the exclusion of sunlight; many of these problems end up in court or worse still, the local accident and emergency room. Here is the law as it stands in Britain

- If Leylandii or another form of hedge is encroaching on a neighbour's garden, the neighbours is entitled to trim back the hedge to the boundary themselves, but must return the trimmings to the owner. That solves the sideways growth of the tree, but a neighbour is not entitled to reduce its height. This is where your people skills will be put to the test as you try to convince your neighbour to top his trees.

- If the neighbour digs his heels in and stubbornly refuses to reduce the height of the hedge, then you can contact you local council. A complainant must prove they have tried to resolve matters privately first before approaching their local council. If the council deems the hedge excessive, they can then order it to be reduced in height to two metres.

- Failure to comply with this order could mean a fine of 1,000.