The Hampton Court Palace Flower Show, with some 50 gardens and 700 exhibitors, is not just larger and more spaced out than Chelsea: it has its own identity. The palette of flowers is different – crocosmias, dahlias, echinaceas, achilleas, Hemerocallis (day lilies) and agapanthus take centre stage – and this year fruit and vegetables almost outnumber ornamental plants. Fruit is imaginatively trained as stepovers and standards or is espaliered and fan trained; vegetables spill out of wine boxes, raised beds, rubber tyres and wicker hanging baskets or scramble up an array of supports.

Unusually, children have a strong presence in the show too. In Chris Beardshaw’s exuberant Learning Outside the Classroom garden (winner of the Tudor Rose Award), children from more than 30 schools grew plants and made the artefacts – shiny bird scarers for the fruit and veg areas, mobiles stuffed with nesting materials, a giant spider sculpture, carved from rhododendron stems. An inspired model (which happily is being reassembled after the show at the Birmingham Botanical Gardens) for how children can learn through growing their own veg, exploring the woodland floor or simply sitting on a grassy mound, in a glade of pyramidal Turkish hazel trees ( Corylus colurna), watching the insects in the meadow below.

In the much smaller but equally inventive Learning to Look After Our World garden, (Best Small Garden) the children of Alton Infant School made mosaic stepping stones, fat-bellied scarecrows and filled wellington boots with flowers. The deputy head, Ann Foulkes, who runs a garden club at the school, wants to show other teachers how it can be done using recycled materials: “We used left-over building materials for the path, and the children brought in tiles from home to make the mosaic shapes for the stones.”

In fact the show gardens offer environmentally friendly alternatives to concrete slabs or imported stone for paths and terracing, from crushed clam shells (a good burglar deterrent too) and tiles from recycled glass to paths of crushed brick and ceramics.

The environmental message is stylishly interpreted by Fern Adler and Heidi Harvey in their Full Frontal front garden. A matrix of colourful beds filled with low-growing plants is separated by strips of permeable paving wide enough to accommodate car wheels, which are interplanted with ferns and other shade lovers. The garden is a response to the RHS’s recent Front Gardens campaign which points out that we are rapidly paving over our front gardens – London has lost the equivalent to 5,200 football pitches – which is increasing the risk of flooding because of run-off into the overburdened drains, and depriving wildlife of places to feed and shelter.

Even the Rose of the Year 2008, unveiled in the Festival of Roses marquee and available this autumn, has environmental credentials. Rosa ‘Sweet Haze’, a blush-pink small-shrub rose bred by Rosen Tantau and introduced by Pococks, has clusters of single flowers with golden stamens that are magnets for bumblebees. Rachel Prior, who uses it as a signature plant in the Life Long Living small garden, says: “Within half an hour of putting the plants in, we had bees visiting them, and they choose it in preference to any other flower in the garden.”

In Floral Marquee 2 Rosy and Rob Hardy’s Turnstile display shows how our tastes in plants have changed. On the modern side are colour-co-ordinated plantings that include new shades such as toffee-coloured Heuchera‘Caramel’ and burnt-orange Echinacea ‘Arts Pride’. On the traditional side are the bright reds, blues and yellows of coreopsis, heleniums, agapanthus and dahlias that were in vogue a generation ago. This is also the theme of Eliz-abeth Stoner’s show garden, Then and Now. Split into two identical-sized plots, the contemporary garden uses a small selection of clipped and architectural plants planted in symmetrical patterns. The 1940s garden, complete with coal bunker, washing line and crazy paving, is a riot of bedding plants and herbaceous perennials planted through the two borders that frame a neat strip of lawn.

For a second year, Hampton offers a category of show garden – the conceptual garden – where the judges pay as much attention to the innovative and creative aspects of the design as the horticultural excellence. Last year several of these gardens looked much like any of the other small gardens. This year they are provocatively different, especially Tony Smith’s In Digestion (Best Conceptual Garden), a black-and-white installation that suggests a giant digestive tract, lined with a rippling band of carnivorous plants. Microscopes allow visitors to watch the plants devour insects.

Near by is the elegant design of Sim Flemons and John Warland entitled The Fallen which suggests a tranquil cemetery whose graves are covered with lush meadow plants. The Portland headstones, however, are carved with the names such as Arnoseris minima(lamb’s succory) and Galeopsis seg-etum (downy hemp-nettle) and are a rollcall of species that are now extinct in the British Isles. Hampton is indeed its own show.

The Hampton Court Flower Show continues until Sunday July 8, 10am-7.30pm (5.30pm on Sunday). For tickets call 0870 842 2234. For details of the awards, visit www.timesonline.co.uk/hamptoncourt

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