VAL BOURNE offers tips on growing a gardening favourite - elegant wisteria

Gardeners love wisteria for its elegant early-summer flowers which hang down so charmingly. Forms have been grown on the sunny side of British buildings for hundreds of years and some of the most impressive specimens may well be double centenarians for wisteria is a tough survivor once the roots are down.

There are two fine specimens in North Oxfordshire. One gnarled wisteria adorns the White Lion Inn in Banbury, clinging to a circular staircase. Another fronts a private house on the main road through Bloxham.

There are six species and they are natives of eastern Asia and North America. Japanese wisteria (W. floribunda), was introduced in 1830. It will reach 4m (12ft) and usually produces small flowers on slender racemes which measure between 12 and 25cm (6-10in) in length. This less vigorous climber is ideal for bridges and pergolas.

If you want to know whether you are growing W. floribunda look at the stems. They twine in a clockwise direction. The star is Multijuga', often still sold under its old name of Macrobotrys'. This form produces the longest of any wisteria I know. They can reach a metre in length but 20 inches is more usual.

The showy climber seen spanning buildings is probably Chinese wisteria (W. sinensis), introduced in 1816. This twines in an anticlockwise direction. It's more widely grown because it produces larger, fragrant flowers on fuller racemes. These can measure a foot in length (30cm). Caroline' has deep, purple-blue flowers which are very fragrant.

If you want to plant one, look for a grafted plant when it's in flower. The bumpy graft on the stem should look smooth and strong and the flowers should be a vibrant colour. There are too many wishy-washy wisterias on sale. White wisteria, although lovely, can be difficult against many building stones. But a clean white can look elegant used with brick. A good, strong lavender-blue is the ideal and there are lots of Georgian and Victorian houses in Holland Park in West London decorated with a splendid clone. The flowers look sensational seen against white-painted stucco.

The secret of success is a warm position and two-stage pruning, but only once your plant is a mature specimen. Leave young plants alone and concentrate on training the framework of soft stems.

Once your wisteria is established it will start to produce long, leafy side shoots in summer. These are long whippy growths and they are easy to spot. Once they appear get the step ladder out and snip them back to five or six leaves. Cut well clear of the buds to prevent damage. This technique produces more flowers and you shorten redcurrant and gooseberry shoots to five or six leaves in exactly the same way.

In midwinter the same wisteria side shoots you pruned in summer are cut back again, but this time to three or four buds. Do this and your wisteria will flower profusely. Further more you will be able to see them clearly against a background of refined pinnate leaf.

Congratulations to Mary Spiller, of Waterperry Gardens, on receiving the RHS Associateship of Honour. Mary's award, which was sponsored by Chisholm Ogg, a member of her enthusiasts' class at Waterperry, and Ken Burras, the former superintendent at Oxford University Botanic Garden, recognises a lifetime of teaching and practising horticulture.