A sea of clematis with 40-metre 'waves' of white and pale purple blooms, and a splash of burgundy, has brought Raymond Evison his 29th gold medal at this year’s RHS Chelsea Flower Show.

In the Grand Pavilion he was all nerves as the judges scrutinised the five huge, undulating frames of clematis but there was nothing to fault from the man who probably knows more about clematis than anyone else on the planet and he also collected the RHS New Design Award.

Raymond grows more than two million plants in this Guernsey Clematis Nurseries and his quality products are sold around the world, including the Potted Garden Nursery, in Bearsted, near Maidstone.

Raymond moved from the UK in the 1970s to take advantage of Guernsey’s milder climate – it sees around 2,000 hours of sunshine a year and barely a frost.

A visit to his greenhouses is the pièce de résistance for garden groups who make an advance booking to visit his nursery.

Quality is king (Raymond supplies the Queen and HRH Prince Charles) and he offers information for beginners to professionals, explaining growing methods and his painstaking efforts to trial and introduce new plants for today’s market; smaller, more compact clematis with flowers that bloom from top to bottom.

Raymond said: “Garden trends are ever changing but new houses are being built with smaller gardens so we know that breeding plants for patio containers is the way forward.

“People have less space and they are often short of time so they want plants that are easy to look after. There is a misconception that clematis are difficult to grow but gardeners just need to know when to prune them.

“There are three different pruning groups which correspond to the time they flower - early season flowering, mid-season flowering and late-season flowering. All clematis, whichever group they belong to, need a severe haircut in their first full season and should be cut back to 12 inches to encourage growth.

Raymond's tips to tip top clematis

Pruning Group 1 - such as armandii and alpine: Just tidy up after flowering

Pruning Group 2 - early large flowers in mid-season: At the end of winter/early spring cut the dead and weak steams down to a strong pair of axil leaves

Pruning Group 3 - such as terniflora. M.Koster, Royal Velours: At the end of winter or early spring, just before new growth begins, remove all of the previous season’s stems to just above ground level.

“It really is that simple and when you buy from a reputable nursery they can also offer advice.”

Amanda Brookman, of the Potted Garden nursery, Bearsted, says the clematis supplied from Raymond Evison’s nurseries are ‘the best quality’ with many new plants being introduced every year.

She said: “We tend to supply serious gardeners and they are always on the look out for new varieties as well as old favourites.

“The new Patio and Garden family from Raymond Evison promises to be interesting, although Rebecca, which I think was named after his daughter, remains a top-seller.”

Raymond Evison’s new book Clematis For Small Spaces, 150 High-performance Plants for Patios, Decks, Balconies and Borders is available from amazon.co.uk, price £20

More details on Raymond here