Orchestral manoeuvres: Cleve West's Chelsea Flower Show design left a lasting impression

Its repetition of plants – much like a musical refrain – is the key to good design, says Anna Pavord.

It was a year of retrenchment at the Chelsea Flower Show, with its "let's not show we're spending too much money" gardens. The general trend was rather conservative: lots of grey and silver in the borders, old roses, spurges, iris and not a banana in sight. Cleve West (clevewest.com), the most modest man on Main Avenue, got a richly-deserved Best in Show for his elegant garden of pillars, rills, topiary and borders knitted through with crambe and annual orlaya.

Most of us who garden understand plants much better than we do design. It's hard to talk about abstract concepts like mass and void. Much easier to swoon over the cornflowers and valerian, both of them much in vogue at Chelsea this year. But the voids, the spaces in a garden, give our eyes a chance to rest and so make the next piece of planting stand out more vividly. The complexity of Cleve's borders would not have been so memorable had they not been set against the big plain hulks of clipped yew and the restrained courtyard of stone setts towards the back of the garden. Steve Swatton (swattonlandscape.com), was the man responsible for the superb dry-stone walls and pillars.

The borders, both in Cleve's creation and other show gardens, had a particularly joyous freshness about them. The cool weather through April and the first half of May seemed to suit plants, particularly ones such as thalictrum and monkshood which bulk up into really handsome clumps if they have plenty to eat and drink. Both have good foliage, so they earn their keep even if they are not in flower. Cleve used the white-flowered meadow rue (Thalictrum aquilegifolium 'Album') in his borders, along with a pale monkshood (Aconitum 'Ivorine') and the tall, fat stems of Valeriana officinalis. This is a completely different plant to the one we commonly call valerian. That's the one that seeds itself, both the pink-flowered and the white-flowered kind, so liberally into walls.

Valeriana officinalis grows tall, up to 2m (6ft), and its strong stems spearing way up above its neighbours were a connecting thread between several Chelsea gardens this year. It's odd that this should happen because valerian isn't a new plant. It's a British native, once important as a medicinal herb (all plants that carry the officinalis tag were once used as medicines) and its common name, all-heal, suggests how important it once was. Gerard, author of the famous Herball (1597) says it "do purge upward and downeward". Sounds noisy.

The leaves are deeply cut and make a bold, fleshy clump before the juicy stems start to shoot skywards. The flowers themselves are tiny, borne in pinkish-white clusters that push out from the axils of the leaves. It flowers over a long period and then you need to deadhead fast, for it is a ferociously successful self-seeder.

At Chelsea, the valerian flowers hadn't yet started to open and this was another aspect of the show gardens that I liked. They didn't look as though they'd been pumped with amphetamines, as they sometimes do, with all kinds of plants that wouldn't normally be seen together, pushed into uncomfortable short-term relationships. Looking out over the plantings you could see that there were plenty of treats still to come.

Repeating plants is a well-known way to give a sense of cohesion in a border. It's like a refrain repeated in an orchestral piece. You recognise it as the same thing, though it's subtly different each time.

In an orchestra, that might be because when the tune reappears, it's taken up by a different group of instruments. When key plants are repeated in a border, they will be used with different companions. So in Cleve's border, the airy heads of crambe were partnered first with campanula, then with tall Euphorbia wallichii, then with Siberian iris, either slender violet-blue 'Tropic Night' or ivory-white 'Gull's Wing'.

Another characteristic that gave freshness and vitality to so many of the Chelsea borders was the use of annuals. Corncockle, ammi, snapdragons, cornflowers, love-in-a-mist, orlaya, nigella and poppies of various kinds were all important players in Cleve's borders, especially the orlaya, which was in full, flat white flower and looked gorgeous. You might now be grunting crossly that they must have forced the plants in order to get them to flower in May. But it's not true. If you sow seed of any of the annuals I've just mentioned in early September rather than in spring, you will get fat, well-grown plants to set out in late March. Then they'll be in flower by late May.

I sowed seed of the cornflower 'Blue Diadem' (Thompson & Morgan £2.29) on 10 September last year. They germinated within two weeks and when the seedlings began to look crowded, I pricked them out into individual pots (7cm/3in). Early this March I shifted them into bigger pots (12cm/5in) so that by the time I set them out in early April, they were already substantial plants.

Reading this, you might think: "Just too much faffing about". But it's wonderfully soothing, sitting with a pile of pots and a bag of compost, potting on. Especially when you know the end result is going to be so stunning. Our cornflowers have been flowering since the end of May on plants at least 120cm/4ft high. Since each plant has between 15-20 flowering stems, the display will go on a long time yet.

You need space to set out the pots, but you don't need heat. All the annuals I've mentioned (except the snapdragons) are hardy. By sowing in autumn, we are just mimicking what they do themselves. Orlaya, which I grew for our garden last summer, dropped a lot of its seed into the rammed stone path that goes up the bank. These self-sown plants were all in flower by late May. Which was a bonus, because I forgot to sow them myself last autumn.

I often sow a second batch of seed in spring and follow the same potting-on routine. But being annuals, these spring-sown plants are in a great hurry to fulfil their destiny. They want to leap straight into flower rather than pause to make a decent clump first. So you never get plants with as much presence. It's too late now to sow the annual flowers that looked so beautiful in the Chelsea gardens. But you can raise plants just as good if you sow seed this September. I've already got orlaya standing by. Avon Bulbs has increased the range of seed they sell and I bought a couple of packets from their Chelsea stand. They got a gold. Natch.