Floral fireworks

Fittingly named after the Greek goddess of the rainbow, the many-hued bearded iris provides a bold explosion of colour to light up any garden, says Ursula Buchan

“As a dependable rule of thumb, the shorter the iris, the earlier it flowers”

I SOMETIMES WISH we had called our daughter Iris, although she might not have thanked us for it. For me, it is a name of infinite romance, since Iris was the Greek goddess whose task it was to carry messages between heaven and earth, crossing between them by a rainbow bridge that she painted in the sky. And, what’s more, she wore a coat of many colours to do it. It’s such an appealing conceit that it’s no surprise that her name was given to the plant genus Iris, as no other group of plants can boast such colour variety. Since childhood, I have loved irises in almost all their iterations because of that mad generosity, which – depending on the kind of iris – enriches the garden from late January until mid-june.

Irises come in two main types, defined by whether their storage organs are ‘bulbous’ or ‘rhizomatous’. I shall discuss the bulbs, which flower in late winter and early spring, another time; here I want to extol the virtues of bearded irises: handsome flowers with distinctively ugly, knobbly, sausage-like rhizomes. Bearded irises are so called because they have clumps of fine hairs on the ‘falls’ (bottom petals). They are classified according to their size; the British Iris Society, the fount of knowledge on these fine points, identifies ‘miniature dwarf’, ‘standard dwarf’, ‘intermediate’, ‘border’, ‘miniature tall’ and ‘tall’ but most home gardeners simply distinguish between dwarf and tall. As a dependable rule of thumb, the shorter the iris, the earlier it flowers. The standard dwarf bearded irises (or SDBS for short) flower in late April and early May, while the tallest ones bloom more than a month later. The moment that the SDB ‘Melon Honey’ unfurls its charming flowers – the colour of cantaloupe melon flesh, with a white ‘beard’ – I know I can look forward to at least six weeks of flowering pyrotechnics from the Iris family. (And some varieties are ‘remontant’, which means they bloom again in autumn.)

Miniature irises grow to 20cm, with flowers of a size to match the diminutive height, while SDBS can reach 40cm. Short irises look well if planted in troughs and other large containers, in rock gardens or the front of garden borders. Those with scented flowers should be planted in pots so they can be brought into the house.

The intermediate varieties, which flower two weeks later, grow up to 70cm. They are not that widely grown, people seeming to prefer the tall ones, which make the most border impact. ‘Miniature tall’ (the best for cutting) and ‘border’ irises grow to about 70cm, while ‘tall’ varieties can reach as high as 100cm. There are literally hundreds of these, from white ‘Winter Crystal’ to pale-blue ‘Jane Phillips’, gold and brownish-purple ‘Bold Encounter’ to deep-purple ‘Superstition’. Nurseries specialising in bearded irises, of every size, include Claire Austin, Broadleigh Gardens, Seagate Nurseries, The English Iris Company, Chailey Iris and Kelways.

Rhizomatous irises soon get overcrowded and stop flowering as freely after three or four years, so need to be revived by division. Propagating any rhizomatous iris you already grow is not difficult but it does have to be done carefully and, if you garden on a heavy soil, you will have to add grit and compost to lighten the clay. Any time in summer or early autumn, after the plant has flowered, simply cut back the ‘flag’ leaves by half with sharp secateurs, thus revealing a fan; dig the rhizome up; snap off and discard the oldest part; and replant the youngest piece (with ‘flag’ fan attached) in a shallow trench of light, gravelly soil, spreading out the roots, so that the rhizome itself is sitting just on top of the soil. Any deeper and you risk losing the rhizome to rot in a wet winter. Lightly tread the soil round it and, if you like, peg it down with bendable wire until the roots establish.

If you can point the rhizomes due south, so much the better, since the sun will strike them for longest in summer; this ‘bakes’ them and encourages the formation of flower buds. That’s because these irises originally hail from Asia Minor and the Mediterranean littoral, and are as keen on sunbathing as any Brit on a fortnight’s holiday in Majorca. Like the swift goddess after whom they are named, garden irises soon fly over the rainbow bridge and are gone but they leave behind a most pleasant, technicolour memory.