Despite all the high-brow hullabaloo surrounding the Chelsea Flower Show, the stars are undoubtedly the plants and trees, many of which will be seen by the general public for the very first time.

Here are some of the new varieties to watch out for:

If ever there was a flower designed for Chelsea, it would have to be the iris. Cayeux Iris, from Gien Cedex, France, Europe's leading iris breeder, is exhibiting for the third consecutive year and has no less than seven new varieties, from the subtle tones of 'Romance' and 'Clownerie' to the dazzling 'Coup de Soleil'. And Richard Cayeux’s dream of creating a pure black and white iris is one step further on with the superlative 'Noctambule' (see picture gallery of all the new varieties).

There is always a buzz around the new blooms from the rose growers at Chelsea. Harkness Roses has four new introductions: ‘Carris’ is a brilliant scarlet hybrid tea - its name chosen by the winner of a BBC Children in Need 2006 auction (see picture); ‘Belmonte’ is a lumnious white/apricot floribunda with a slight citrus scent (see picture); ‘Henrietta Barnett’ is an exotic gold floribunda with an equally spicy myrrh fragrance (see picture); ‘Parky’ is a delicate cream shrub rose with apricot flush, named after TV presenter Michael Parkinson (see picture).

Streptocarpus specialists, Dibleys Nurseries, are launching three new varieties of Streptocarpus: 'Seren', which is Welsh for star, has unusual blue markings set on a yellow flowerhead (see picture); ‘Chloe’ has pale pink flowers with red-purple veins on the lower lobes; and ‘Iona’ has purple flowers, fading to an orangey/red around the throat.

Hillier Nurseries, among other things, is the largest grower of trees in the UK. New plants, shrubs and trees making a first appearance include the wonderful Silk tree (Albizia julibrissen) ‘Summer Chocolate’ (see picture), a form bred by Masato Yokoi in Japan in 1990; Juncus ‘Curly Gold Strike’, a waterside Corkscrew rush with a gold line that twists and curls along leaves and stems (see picture); Berberis thunbergii ‘Golden Torch', a small formal shrub with upright habit (see picture); Phormium ‘All Black’, a New Zealand flax named after the ‘All Blacks’ rugby team; Spiraea vanhouttei ‘Gold Fountain’, with an unusual arching habit, yellow leaves and tiny white flowers (see picture); and Cornus sericea ‘Hedgerows Gold’, a dogwood from the United States with burgundy red stems in autumn (see picture).

Knoll Gardens are specialists in grasses and perennials. Introductions include Panicum virgatum ‘Dewey Blue’, a drought-tolerant grass with blue foilage which hails from the coastal dunes of the United States (see picture), and the evergreen grass Muhlenbergia dumosa has slender bamboo-like stems with fluffy, cloud-like foliage (see picture) - the growers hope it will be seen at the show for the first time in bloom with its soft yellow-white flowers.

A traditional visitor to Chelsea is Hardy’s Cottage Garden Plants, attending its 16th show. The nursery has three quite different introductions: Verbena ‘Seabrook’s Lavender’ (see picture) was found by gardening correspondent Peter Seabrook growing in his Essex garden. This short-lived perennial has over wintered reliably for the past seven years and flowers freely from May to December. Physocarpus ‘Lady in Red’ has striking bright young foliage colour and is suitable for the smaller garden (see picture). Salvia patens ‘Dot's Delight’ grows vigorously from the base and has unusual two-tone blue flowers (see picture).

Pelargoniums are vivid and showy annuals, extremely popular among many gardeners - and the new introductions from specialist growers Brian & Pearl Sulman are no exception. They plan to introduce seven new varieties: 'Royal Prince' (Regal) - raspberry red and light pink petals with a white centre; ‘Southern Frills’ (Angel) - lilac with a purple blotch; ‘Suffolk Salmon’ (Regal) - as its name suggests is salmon with a white centre (see picture); ‘Cottenham Cheer’ (Angel) - tiny pink flowers, some white with pink veins (see picture); ‘Brookside Free Spirit’ - a miniature zonal with double dark pink flowers; ‘Brookside Polka’ - a dwarf zonal with spotted double light pink flowers; ‘Brookside Tango’ - a miniature zonal with double salmon flowers.

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