VAL BOURNE on the ability of irises to repeat flower in the autumn

The Indian Summer has so far failed to arrive. It’s been more like November in Cardiff — warm, grey and wet — with apologies to the rugby capital. So I have been clutching at straws in the garden for little is flowering well. But a Suffolk nursery on the eastern side of England, Woottens of Wenhaston, has reported that their bearded irises are better this September than ever. Apparently, the trials field is awash with colour and scent.

‘Dutch Chocolate’, pictured, is one that’s putting up another fight. ‘Autumn Circus’, clean white veined in violet, is another. ‘Blatant’, a mahogany with yellow standards, is also repeat-flowering along with the blue ‘Cee Cee’. (The full list is on www.woottensplants.co.uk, or call 01502 478258.) This ability to re-flower in autumn is known as remontancy. Iris growers generally find it inconvenient. They prefer irises that flower in summer and then die down before being split up and sold. Whether you like it or not — and I’m not totally sure how I feel about a frilly iris in autumn — remontancy tends to be unpredictable. Irises generally only repeat flower if they are fed after flowering the first time and if the weather is warm and damp in late summer.

The two most famous remontants are the lavender-blue ‘Lovely Again’, bred in 1963, and the refined and ruffled ‘Victoria Falls’, winner of the Dykes Medal in 1984. This medal is akin to an Olympic gold and Dykes, an Irish hybridist who was secretary of the Royal Horticultural Society about 1920, championed clear colours, not wishy-washy pastels. He also preferred ‘selfs’, those with flowers the same colour all over.

Remontancy used to be even more in the lap of the gods in central counties such as Oxfordshire, because most tall bearded irises are much more likely to re-bloom in the bottom third of England where temperatures are highest. I call this the banana belt.

Changing weather is probably altering this pattern. However, one white iris with faint violet veining, ‘English Cottage’, has always re-flowered all over the country. So this is one to seek out if you want a late iris.

Bearded irises enjoy sun and good drainage and they need to have their bare toes baked in summer sun. Therefore they are best grown at the base of a sun-baked wall or on their own in a sunny border as they need space. Their rhizomes, which need to face south, ideally, eventually sit on the soil’s surface when fully happy.

When you plant new irises or divisions always bury the rhizome so that it sits about half an inch below the surface of the soil. As the rhizome develops it will push upwards. Trim off the sword-shaped leaves to between 6in and 8in or so before replanting. Both measures prevent wind rock and now is an excellent time to plant them. A September tidy up of the foliage is also a good idea.

New rhizomes are formed every year. So every three years or so you need to lift your bearded irises and break off the old woody rhizomes and replant the young, paler pieces, discarding the rest. Add some bone meal to the ground — you never know there might be a second flush.

There are six categories based on height from miniature through to tall. Usefully they flower in order, the shorter the bearded iris the earlier it flowers. The miniatures begin in April and the tall ones flower in May, often in time for the Chelsea Flower Show.