Controlling nature; gardening

It's time to think about clipping yew hedges, says Sarah Raven. Unlike most plants, yew can withstand savage cutting back, and if you collect your trimmings as you go, they can be used to make a drug that increases life-expectancy in cancer patients

YEWS ARE living architecture. No other plant is capable of making such beautiful garden structures. A tightly clipped yew hedge has, visually at least, all the solidity and geometry of a real wall. Seen from a distance, the fine grain of its foliage provides an almost seamless black-green boundary to a garden. Close up, though, it becomes a different thing; feathery, dark, full of mystery, one of this country's most magical and alluring of trees. Forget its reputation for smartness, its Cotswold manor conventionality. That doesn't do it justice.

If you have one in your garden, it should be clipped any time between now and November. If you haven't bothered to cut it back for several years, but want to get it under control, be savage. I've seen overgrown hedges cut back so hard that all you can see for months is a mutilated central trunk with a few bare branches, stripped of their evergreen leaves. This sort of treatment will kill most plants, but not yew. New growth will erupt in the spring and within a year you will have created a perfect hedge.

If your hedge is just in need of a trim, you can either do it meticulously, or go for a more organic, baggy shape. My favourite yew hedge is the one at Blickling Hall in Norfolk, where the 20ft hedge is cut in a sofa-like shape with lots of creases and bulges along the way. There's no better backdrop to an expanse of lawn.

To clip it correctly, you should remove nearly all the new growth. If you fail to cut the plant right back to the same place every year, you will add inches to the width of the hedge and it will slowly take over the paths or flower beds. For short lengths of hedge, use old-fashioned shears. If you prefer to use a machine, the electric version creates less vibration and is lighter to handle than its petrol-driven equivalent. Make sure the blades are sharp as mashing up the stem ends will encourage disease.

To cut your hedge in a perfectly straight line, you will need a couple of canes the height of the hedge, a shorter cane, some string, a spirit level and a plumb line. If your hedge or topiary is over 7ft high, you'll need a platform to work from, too. Either make a platform with a sturdy plank stretched between two stepladders, or buy a stand specifically designed for the job. There is such a thing - a Henchman - which is a platform on wheels with ladders and rails. These are very sturdy, safe and easy to move around.

Once you've got your stage arranged, stick the long canes in at either end, attaching a string at ground level a few inches into the hedge to mark how much greenery you need to remove. Attach another string at the height you want your hedge to stand. Poke the shorter cane through the top of the hedge horizontally, and hang your plumb line from that. It will hang down marking the line that you should cut. Move it along as you go, using the spirit level to create a perfectly flat top.

Save your trimmings as you go. There is a compound in English yew (Taxus baccata) that plays an important role in the treatment of several cancers, and if you have a minimum of three black bin liners full, you can send them to be used in making an anti-cancer drug.

They have to be freshly cut from the English yew, not Irish or golden yew, and they're only useful if they come from a hedge that is clipped at least once a year. The key substance, Taxol, is produced in much greater quantities in new growth. If the clippings are left for more than 24 hours they will heat up and start to ferment, destroying the precious Taxol, so you need to arrange a pick-up before you start to clip.

The potent medical effects of Taxol weren't discovered in the West until

the 1970s, though native American Indians had been using the bark of Pacific yews (Taxus brevifolia) for generations to treat ailments as diverse as rheumatism, scurvy, and lung and bowel complaints.

Taxol, which occurs at 10 times the potency in the foliage of young English yew, halts the division of cells, and if you can introduce it directly into a tumour, you can stop the dangerous free-wheeling growth of the cancer. It isn't a miracle cure, but used where conventional chemotherapy fails, it significantly increases life expectancy in people with specific types of cancer, and is particularly effective against breast and ovarian tumours.

Yew Clippings Ltd will arrange for storage bags and couriers to be sent: 01308 485693

There*s something to be said for rejecting this meticulous method. Why not prune your hedge into a more organic, baggy shape. There are no nicer yew hedges than those at Blickling Hall in Norfolk, where the twenty foot hedge is cut in a sofa-like shape with lots of creases and bulges along the way. There*s no better backdrop to an expanse of lawn. If you haven*t bothered to prune your yew for several years, but want to get it under control, be savage. Yew is remarkable in being able to take very drastic pruning. I*ve seen overgrown hedges cut back so hard, that there*s no greenery left on the plant. All you see for a few months is a hideous mutilated central trunk with a few bare branches, stripped of their evergreen leaves. This sort of treatment will kill most plants, but not yew. They will take a while to recover, but new growth will erupt in the spring and within a year, you*ll have created the prefect hedge. What*s more, now you*ve got it pruned, you*ll be able to send your clippings for cancer drugs next year. You can buy a *Henchman* from Heygate Engineering, Manor Farm, Hannington Tadley, Hants RG26 5TZ Tel 01635 299847 Fax 01635 299024 From pounds 329 for the smallest model.

Yew Clippings Ltd (01308 485693) will arrange for a special storage bag and a courier to be sent.