Gardening: The art of planting

I'm standing with the award-winning designer Sarah Price in a huge polytunnel in Hampshire. We're looking at a vast sea of green plants: hostas, columbines, foxgloves, spurge, geranium, comfrey, iris and, most particularly, the tufted hair grass, Deschampsia cespitosa. This is a key plant in Sarah's design for her show garden at The Chelsea Flower Show, which opens on Tuesday.

The garden is inspired by the landscape of the Black Mountains in Wales, which she knows well. She's planned a calm, contemplative space, with meadow planting meeting a mirror of water, earth banks, drystone walls and pools of the dark cow parsley, Anthriscus sylvestris 'Ravenswing'. The meadow is veined through with perennial plants – lime, cream, white and yellow – with spreads of deschampsia providing the underpinning. By late spring, this is usually coming up to flower but it's been a chilly season. The fat tussocks in their big pots are as green and healthy as can be. But they are showing no signs of producing the tall airy stems that Sarah had visualised.

The polytunnel, crammed with plants destined for Chelsea, is at Hardy's Cottage Garden Plants nursery and the owner, Rosy Hardy, has already shifted a third of the grasses under high-pressure sodium lights to extend the hours of daylight. If necessary, they can bring in some heaters as well, though in 14 years of producing plants for Chelsea gardens (and their own stand as well) this is something they've never had to do. The good news is that it is easier to push plants on than hold them back. "Well, for us it is, because we don't have much refrigerated space," she explains. But the bad news is that while the deschampsias are holding back, the columbines have suddenly shot ahead. Sarah needs plants with colour, but with enough buds to sustain the Chelsea display through a long, tiring week. If the plants are in full flower at the beginning of the week, they will have shot their bolt by the end.

All this knowledge has come to her rather fast. She did her first show garden at Hampton Court just two years ago and though the budget (£6,000) was tiny by most designers' standards, she won a gold. She was at Chelsea for the first time last year and scooped up another medal for her gorgeous Bejewelled Garden: purple, brown and gold jewel flowers floating in a matrix of the sedge Carex comans. It was a wonderful creation, rather like an abstract painting. But, like her Hampton Court garden, it was small.

This year, she's working with the landscape architects Wynniatt-Husey Clarke in a much bigger space, and with a bigger budget (£60,000), provided by the shopping channel QVC. This Chelsea show garden, on Royal Hospital Way, is 10x15m, which represents a lot of plants. "You've got to hold your nerve," Rob Hardy, Rosy's husband says to Sarah, as discussion in the polytunnel moves on to the meadowsweet, Filipendula ulmaria, a British native that loves damp, marshy places and produces huge creamy heads of flower. The Hardys have set aside 36 huge pots of it for Sarah's garden. But there are no spares. Will the double-flowered kind, 'Flore Pleno' do as a back-up if she finds she needs more? Or if a lorry should back into their plants as they are planting? Space at Chelsea is very tight.

Sarah is heroically calm. There's a vision in her head and, in gardening terms, it's almost the most difficult vision to achieve: a mirror of nature, planting that is aesthetically pleasing and yet real, naturalistic yet necessarily contrived. The planning started more than a year ago, when she sent a planting list to Rosy Hardy with an estimate of the number of plants that she'd need. But once work starts on the Chelsea garden (she'll have been planting since Wednesday) she has to trust her instinct as to what feels right, what works. It's different once the plants are real creatures in front of her, not concepts on a page.

She's 27 years old and her success, in this overcrowded world of garden design, has been extraordinary. How did it happen, I asked, in a brief moment between the kingcups (Trollius x cultorum 'Alabaster') and the thistles (an incredibly handsome stand of Cirsium heterophyllum). Fine art seemed to be the answer. She trained as a painter and it is this feeling for colour, tone, texture, that sings out in her garden designs. She followed her foundation course at Kingston with a Fine Art degree at Nottingham Trent, where film, installation, photography and other sirens called her away from painting. "But it was all such temporary work," she says. "I couldn't see how I could make a living from it." She loved gardening, having grown up with gardening parents (it doesn't always happen that way) and so for a year worked as a gardener at Hampton Court Palace. Finally, she did a garden design course, though looking back, she thinks that was not as useful as her background in art, and, particularly, her practical experience as a gardener.

That gives her a very real appreciation of plants, their needs and potential. And the cirsiums in front of us now are getting universal approval. They are at exactly the right stage of development. "You'll have three or four flowers open on each of those," says Rosy as Sarah turns the plants round, looking at the handsome divided foliage. When the wind blows through the Chelsea garden, they'll show their silver undersides and the stems are strong enough not to need staking.

Though it's exhausting, she actually quite likes the pressure of a show garden and the success she's had at Hampton and Chelsea has brought her lots of work. "I need to be challenged, continually. I can't repeat myself. And I've got to be completely happy with the work that I do." So keep your fingers crossed for those deschampsias, and if you're going to Chelsea, look out for Sarah's garden on site RHW37.

The Chelsea Flower Show opens on Tuesday and runs until Saturday 24 May. Tuesday and Wednesday are reserved for members of the Royal Horticultural Society when all-day tickets (8am-8pm) are £46 for Tuesday (£23 from 3.30-8pm and £15 from 5.30-8pm) and £37 for Wednesday (£20 from 3.30-8pm and £13 from 5.30-8pm). All-day tickets for Thursday and Friday cost £41 (£23 from 3.30-8pm and £18 from 5.30-8pm). All-day tickets on Saturday are £41 and the show closes that day at 5.30pm. The big sale of plants starts at 4pm on Saturday. Entry tickets must be booked in advance on 0870 842 2234 or online at rhs.org.uk/flowershows.

Sarah Price can be contacted on 07884 340467 or via her website, sarahpricelandscapes.com; Wynniatt-Husey Clarke Garden Design is at 15 Edburton Avenue, Brighton BN1 6EJ, 01273 555447, whcgardendesign.com