Still going strong: With the warm air and moist ground, autumn gardens can provide the finest spread of all

The rich, still days that we so often get in the first half of October can provide the best conditions of the year, says Anna Pavord

One of the best things about being a gardening correspondent is the cast-iron excuse it gives me to abandon washing-up, shopping and other hideous duties and go gardening instead. The rich, still days that we so often get in the first half of October can provide the best conditions of the year.

The soil is reasonably moist after the September rain, but not so wet that it cannot be worked easily. The ground is still warm and the air, too, so that dahlias are producing enough flowers to dress an elephant, and annuals, such as the superb, spidery cleome, decide that they won't, after all, pack up their bags and leave.

There is an element of lottery about the gorgeous days of October. Nothing can be taken for granted. This might be the last day you see the brilliant blue salvias in bloom. Or the mistier, grey-blue columns of the agastache. This might be your last chance to sniff in scent from the long, white trumpets of Nicotiana sylvestris.

The general perception of the October garden is of gold and yellow and red and brown, a kilim carpet laid on the earth. In fact, there is still a great deal of purple and blue around, from the flowers of tall, thin Verbena bonariensis and the cowled heads of monkshood, one of my favourite herbaceous plants. They are strong, disease-free, unfussy, with good dark foliage as well as a long-lasting display of flowers in blues of every kind, from pale steel to navy.

To get monkshood flowers this late, you need to choose carefully. At Pettifers, Gina Price's fine garden in Oxfordshire, they grow big clumps of one called Aconitum carmichaelii 'Royal Flush'. It's an excellent new variety, not too tall (120cm/48in maximum) with rich blue flowers that, when I was in the garden in late September, had scarcely begun their show. They like good soil but will put up with semi-shade. At Pettifers, they are stars of a curving border planted especially for autumn effect.

Though you do not garden in autumn with anything like the same fervour that you do in spring, it seems a shame to put the garden to bed too early in the year. October may yet deliver some of the most languorous days of the year and, unless you live in a frost pocket, growing conditions are as indulgent as anything you get in August.

Make the most of them. Plant the autumn-flowering cyclamen (C. hederifolium), the best gift (and only £2.99 each) you can give an autumn garden. Plant autumn crocus and brilliant yellow sternbergia. Plant colchicums. The colchicums have been in such a hurry to flower that the buds, piercing leafless through the ground, spear fallen leaves of a snakebark maple on their tips and then open, with the leaf stuck as a ruff round the bare white stem.

TRUMP CARDS FOR THE AUTUMN GARDEN

Include topiary. As colour drains from the scene, the structure that topiary gives is vital. At Pettifers, four tall 'flasks' of yew add drama to views down the garden long after the showy clumps of dahlias round them have finished. A low box hedge, and balls of clipped phillyrea act as anchors in a sea of more evanescent effects.

Plant a tree that fruits. This might be a native tree, such as hawthorn, spindle or rowan, all of which can give superb displays in autumn. Or it might be a more exotic specimen, such as Sorbus vilmorinii (dark red berries, ageing pink, then white), Sorbus 'Joseph Rock' (pale yellow berries, turning orange-yellow as they age) or the crab apple Malus hupehensis (bright red, cherry-like fruit). Gina Price has planted all of these in a little autumn copse towards the bottom of the garden, a beacon of warmth glowing in the mist.

Concentrate your effects. You might have room for only three autumn-flowering plants, but they will sing out more effectively if they are grouped together, rather than marooned between the dying remnants of peonies and iris. In the splendid deep autumn border at Pettifers, the monkshood 'Royal Flush' is partnered with the bronze daisy flowers of Helenium 'Sahin's Early Flowerer' and Aster amellus 'Veilchenkonigin'.

Late-flowering Michaelmas daisies have long been staples of English flower gardens, but the old kinds had flowers the colour of dishwater, were often too tall to stand up on their own and quickly succumbed to mildew. 'Veilchenkonigin' (better known over here as 'Violet Queen') is just 50cm/20in tall, has flowers of deep amethyst purple and is strongly resistant to disease.

Include grasses. Gina Price's favourite is Calamagrostis x acutiflora 'Avalanche'. "It stands up well, lasts a long time through winter and comes through clean and fresh in spring." This variegated form of the feather reed grass has pale green leaves with a white stripe down the centre and tall plumes of purplish-green flower heads that fade to buff brown in winter. Height 120cm/48in. Grasses are included in many of the planting schemes at Pettifers: miscanthus with yellow helianthus, stipa with achillea and sedum, pennisetum with eryngium, pampas grass beautifully silhouetted against tall pillars of Irish yew.

Keep up with dead-heading. For most of us this is easier said than done, but Pettifers is beautifully looked after by a full-time gardener, Polly Stevens. Dahlias, such as the huge clumps of maroon-flowered 'Admiral Rawlings', are regularly cleaned up and so not only look terrific, but give a long season of flower. Helenium 'Sahin's Early Flowerer' (which Polly nominates as her best plant for autumn interest) can be kept going from July until the first frosts, if it's regularly dead-headed.

The garden at Pettifers, Lower Wardington, Banbury, Oxfordshire OX17 1RU is open by appointment only. For details, go to the contact page of pettifers.com