Grow bearded irises These lovely flowers will bring an instant Chelsea feel to any garden

These lovely flowers will bring an instant Chelsea feel to any garden. Val Bourne suggests some names to look out for

You can’t miss bearded irises at the Chelsea Flower Show: nursery specialists Cayeux and Kelways both exhibit in the Great Pavilion, and their stately blooms are always found in the gardens because they peak at the perfect time – in late May and early June. Plant breeders have provided gardeners with a huge range of colours and the beards on the lower petals provide extra colour and pollen for bees. It seems fitting, then, that irises take their name from the Greek goddess of the rainbow, Iris, who travelled from earth to heaven. Irises were often planted on graves because Iris guided people to the afterlife.

Lumpy rhizomes

Bearded irises need sun and good drainage, and produce lumpy rhizomes that sit above the soil. These roots need to be baked by the sun to encourage next year’s flowers, and require space to perform well. Many gardeners trim back the foliage to roughly 30cm (12in) after flowering, so the rhizomes get maximum sunlight. It’s also a good idea to plant them so their roots face the sun. Divide irises after flowering and replant if a clump is short on flowers or if you need more elsewhere. Most taller bearded irises benefit from being divided every third or fourth year. Lift the roots carefully with a fork and select the new plump rhizomes, cutting away the darker, older pieces. Sometimes you can break the roots with your fingers. Plant the young rhizomes just below or on the soil surface because they root better in that position. You can also divide in autumn if it’s more convenient. Although bearded irises prefer alkaline soil, gardeners with acid soil can add lime. If you garden on heavy clay, add coarse grit. The one thing to avoid is a nitrogen-rich feed; instead, use a modest amount of slow-release, balanced fertiliser such as Vitax Q4 (£4.99 for 900g).

Flowers from April

Bearded irises are categorised by height and flower: the shortest bloom in April and the tallest in June. The shortest, known as Miniature Dwarf Bearded irises, are less than 20cm (8in) tall so make great additions to alpine screes or sunny strips. Many gardeners opt for the slightly taller Standard Dwarf Bearded irises (38cm/15in) because these flower by late April. My favourites include white and olive-green ‘Green Spot’ and blue ruffled ‘Sapphire Gem’. One the most useful groups are the Intermediate Bearded irises because these 60cm (2ft) high plants produce several flowers per stem in May. The widely available, deep-maroon ‘Langport Wren’, raised by Kelways, has sultry flowers that stand out against pale foliage. Other good ones are deep-purple and white ‘Katie Koo’ and rich-pink ‘Raspberry Blush’. Tall Bearded irises remain the favourite because they perform as summer approaches. The flowers can be frilly and feminine, as with blue and yellow ‘Edith Wolford’, or bold and dramatic, like rich violet ‘Titan’s Glory’. Dark irises, such as ‘Black Tie Affair’ and ‘Black Swan’, sell out first. However, Chelsea designers often prefer browns and reds including ‘Dutch Chocolate’, ‘Quechee’, ‘Kent Pride’, ‘Natchez Trace’ and ‘Sultan’s Palace’. When it comes to bearded irises you can plant a rainbow of your own.

“Trim back the foliage after flowering so the rhizomes get maximum sunlight”