Chewing the leaves with a tropical taste: Paul Williams, head gardener at Bourton House, has had great fun responding to the challenge to 'bite off more than you can chew', reports Anna Pavord

'THERE must be more to gardening than this,' thought Paul Williams at the beginning of his horticultural career, when he felt permanently attached to a mowing machine on the grassy acres of Cannock Parks in Staffordshire.

He was right. For the past six years he has been head gardener at Bourton House, Bourton-on- the-Hill in Gloucestershire, where he has been discovering, spectacularly, what the plant world has to offer besides grass. The garden is still adjusting to the new clothes that the Paices, its new owners, have bought for it, but what struck me particularly when I walked around it (in pouring rain, of course) were the quantities of tender exotic plants.

By early autumn these are at their best: lush, tropical, leafy, luxuriant. 'Heckish fun,' says Mr Williams. But, as moralists are quick to point out, there is always a price to pay for anything that is heckish fun. In this case, it is whatever it costs to keep the plants frost-free throughout the winter.

Mr Wiliams was turned on to these kinds of plants by the collection at Pershore, the horticultural college in Worcestershire where he finally went for some proper training.

Cannock was not all a waste, though. On a rare moment away from his mower he met Barbara, who was working in the glasshouses. They married, backpacked through Europe until the money ran out, and returned to face Real Life. For Mr Williams that meant the course at Pershore and then the job at Bourton.

By the way he talks about them, you can tell he is nuts about plants. If you mention something he does not know (which is not often), you can hear the computer in his brain whirring away, stashing the new plant and its description in the appropriate place to be retrieved and matched against the plant when he finally tracks it down. As he will.

He touches his plants constantly, urging you to do the same, to feel the sumptuous velvet leaves of Pelargonium tomentosum and relish the peppermint smell that is released when you do so. The aeoniums have a completely different texture. They are like waxworks, toy trees with succulent rosettes of green or purple leaves arranged in perfect symmetry over the plant. The surface of the leaves is as glossy and slippery as a polished stone.

Mr Williams's instructions from his employers, even newer than he to proper gardening, were 'bite off more than you can chew and keep chewing'. That is why he quickly abandoned geraniums, lobelias and petunias in favour of agaves, melianthus, dudleyas and daturas. All these plants are susceptible to frost, so there is an element of lottery about how long the display will continue this month and the next.

The first frost, which in chilly Gloucestershire can strike at any time from the beginning of September, is rarely fatal, as the plants are mostly raised up from the ground in pots, but for Mr Williams it acts as an alarm bell. Permanent fixtures, such as the big spiky agaves and succulent echeverias are moved wholesale in their pots under cover. During August and September he will have taken cuttings of more temporary plants, such as his geraniums. He chooses them for their leaves rather than their flowers, favouring lush varieties such as 'Chocolate Peppermint', which has large, handsome leaves, each with a dark chocolate-coloured blotch in the centre.

Like the Pelargonium tomentosum, it grows quickly, bulks up well in pots and strikes easily from cuttings. Both are available from Fibrex Nurseries, Honeybourne Road, Pebworth, near Stratford- upon-Avon, Warwickshire CV37 8XT (0789 720788).

He also takes cuttings from his tropical-looking fuchsias, such as F. splendens, 'Thalia' and 'Gartenmeister Bonstedt'. These all have lustrous leaves, darker and silkier than those on ordinary fuchsias. The flowers are longer, thinner, with a touch of orange that contrasts brilliantly with the foliage.

All these types are much more tender than common garden fuchsias. 'More interesting though, aren't they?' Mr Williams remarks, whizzing pots around to try the effect of the leaves, first against a steely-grey agave and then against the leaves of a striped Iris wattei in a pot near by.

Putting exotic plants together, especially in pots, is his forte. There is a huge pot, 27ins across, by the raised pool, which he planted up in situ at the end of May. With smaller pots he can cheat, planting things in the greenhouse, then whipping them out already established. This pot was too big to manage in that way.

'I suppose there must be a bit of an arty-farty streak in me somewhere,' he says, looking critically at this particular pot. He said it as though it was a disease, the first step to eternal damnation. And he never stopped tweaking at the pot, snipping off the few dead flower heads, ferreting about inside the foliage for dead leaves that might attract mildew, chopping off strands of helichrysum that had strayed into forbidden territory.

The three big anchors of the pot were melianthus, sea-green star of the foliage scene, and two strappy phormiums, one dark bronze, one lightly variegated. The melianthus leaves unfold from tightly pleated fans into sprays of jagged-edged leaflets. It is the most sumptuous plant ever invented. At the back of the pot was a tall Begonia fuchsioides, which has dark, glossy begonia leaves combined with red bell- flowers just like a fuchsia. It will grow to 4ft in a season.

Weaving between these was the 'Chocolate Peppermint' geranium, as well as another with leaves variegated in cream. There was plenty of grey, woolly helichrysum and a succulent grey lampranthus hanging off the edge.

These are South African plants, relatives of the mesembryanthemums and have the same fleshy sort of leaves, adapted to store water in arid, desert-like conditions. That is not what they have been getting in Gloucestershire this summer, but they do not seem to mind. The fact that they do not flower is an advantage in a mixture such as Mr Williams had put together in the pot.

A hairy grey-leaved dorycnium was only just visible under the exuberance of the geraniums, the grey washed over with mahogany from the seedheads ripening among the leaves. The only flowers were those of a steely-grey argyranthemum 'Chelsea Girl', white daisies with yellow centres and masses of blue-grey foliage, as narrow as pine needles.

He uses a John Innes-type loam compost rather than peat. This is not for environmental reasons but because he believes, passionately, that loam is better for plants. I had a whole riveting lecture on the subject, verbatim, from his Pershore days. It had to do with colloids and platelets and the ability of loam to hang on to fertilisers better than peat.

He mixes Enmag slow-release fertiliser into the compost at planting time, and occasionally gives the plants a boost feed of nitrate in mid-summer. All the plants are overwintered in the same conditions in the greenhouse at a minimum 3-4C. 'Not ideal,' he says, 'but it's all we've got.' The low temperature at least keeps away bugs and dissuades the plants from growing too much and becoming leggy.

Excessive winter damp is the chief danger, especially with plants such as the agaves and the magnificently whorled Dudleya brittonii. Everything is grown in clay pots, rather than plastic. That is partly because the owners like it that way, but it also helps to avoid waterlogging. Clay pots dry out quicker than plastic.

The Paices are lucky to have Paul Williams. But he is lucky to have them, too. Having encouraged him to take the massive bite at the garden, they leave him to get on with the chewing. 'Terrible to work for people who were in the garden themselves all the time,' he says. 'It would completely spoil my fun.'

The garden at Bourton House is open on Thursdays, 17 and 24 September (12noon-5pm). Admission pounds 2. Check in the National Gardens Scheme book for regular openings next season.

(Photograph omitted)