Very few flowers open from November and keep going until spring, but the winter-flowering iris obliges brilliantly by sending up pointed, translucent buds which unfurl to produce a blue or purple iris.
Individual flowers can be picked and brought indoors and then it’s possible to watch the flowers open as you drink a cup of tea. It’s one of the great pleasures of winter.
When to plant
Try to plant this iris in winter or spring (in a garden hot spot) and then nurture it for the first growing season so that it gets established.
Where to plant
Iris unguicularis was originally introduced into Britain from Algeria in the nineteenth century by the bulb collector and botanist Dean Herbert (1778 - 1847). But it’s also found naturally in Turkey, Syria, Lebanon and Israel. These are relative hot spots compared to Britain, so in order to do well here this iris needs a south-facing position - ideally against a wall.
When it flowers
Flower numbers vary from year to year. Hotter, sunnier summers produce more winter flowers - whilst a dull summer can leave you with fewer.
Clumps become quite large over the years, and a mature winter-flowering iris can produce well over a hundred flowers or more. These are rationed out between November and late-February before its final flowering frenzy in March and April.
Caring for winter-flowering iris
Once established, leave it well alone. Don’t water or feed it because it flowers best given dry conditions and poor soil. Iris unguicularis thrives on neglect.
The only maintenance is a twice-a-year grooming, because the clump fills up with dead leaves as they wither. Use a pair of small scissors and snip away at any browning foliage to leave only the green leaves. This must be done every September and it should also be done in May as well. This preening process makes a real difference to the plant.
Clumps can be divided after flowering if needed. But generally these are plants best left to to their own devices.
Pests and diseases
Some forms suffer virus, which can show itself in the stripy leaves. Sometimes the flowers become striped as well. When buying look for good, unmarked green leaves and avoid any that appear a two-tone green.
Look behind the clumps in late autumn and remove any clusters of hibernating snails that are welded to each other – they’re just waiting to snaffle the flowers when they wake up.
These make excellent plants against a sunny wall and I have always grown them in front of winter-flowering clematis (C. cirrhosa) to shade the roots. But you could grow them in large clumps or join them up to form a row. They do need some space, like most irises, so don’t hem them in with other flowers.
The simple species (iris unguicularis) is mid-blue, but its forms differ in colour and flower size.
'Mary Barnard' is a deeper violet-blue and the flowers are flatter and more substantial. This plant was collected by Mary Barnard in Algeria in 1937 but not registered under her name until 1962.
'Abington Purple' has smaller flowers, with curled-back petals that are more navy than purple, and with each petal prominently marked in white and yellow.
'Walter Butt' is a silver-lavender with larger flowers and a floppier habit.
Where to buy
Broadleigh Bulbs www.broadleighbulbs.co.uk