MONTY DON

From bright yellow to deep purple and rich plum, no flower is more intense at this time of year than the winter iris, says Monty Don

Nothing in the garden is more intense right now than the winter iris, says our gardening expert

About five years ago I was filming for Gardeners’ World at RHS Wisley in Surrey on a bitterly cold day in early April. A cruel east wind was making a spring day arctic so I took refuge in the alpine house which, that exceptionally cold spring, was about the only place at Wisley that had some colour. And what colour! I was bewitched by the jewel- like intensity of the flowers, all growing in terracotta pots sunk into sand.

And, among the species tulips and fritillaries, no flowers were more intense than the various irises they had there. I had given up growing winter-flowering irises at that time because they really did not appreciate the combination of our heavy clay and exceptionally damp winters but I immediately resolved to try again – and since then they have been a delight, brightening up the late winter days here at Longmeadow.

Rather than force them to cope with conditions they’re never going to enjoy – all these alpine bulbs can cope with a lot of cold but absolutely hate sitting in damp soil – I now grow my early irises in terracotta pots (that not only look good but have better drainage than plastic ones) filled with a compost mix that is fully half grit so very, very free-draining.

I plant them any time between the beginning of September and end of November. They can be left outside as long as they do not get too wet, but I put mine in a glass frame that’s like an umbrella – open to the cold weather but shielded from the wet. The shoots appear around Christmas and as soon as buds appear I bring them into a greenhouse or windowsill to push them on. This all forces them to flower a little early so we can have a good display in late winter. But none of that is necessary. These are by and large hardy little flowers that will grow in grass, a border or an exposed window box – but always as long as they have good drainage.

Iris danfordiae is bright yellow and one of the first to flower in mid-January. It is compact so looks best in a shallow wide pot, like an alpine pan. It’s not expensive and tends to flower less well after the first year so, for the best display, it’s a good idea to buy fresh bulbs each year.

I. reticulata blazes in February with beautiful deep indigo-purple petals flowering on short stems and looking like an especially glamorous crocus. I have I. reticulata ‘Harmony’, which has particularly deep blue flowers with a gold blaze on the lower ‘ fall’. The leaves remain quite stubby during flowering but then grow taller to reach 30cm (1ft) or more at maturity. ‘J S Dijt’ is a rich burgundy colour and flowers later, so extends the iris season.

I. histrioides is a member of the reticulata group, and ‘George’ is an especially magnificent example, with rich plum-purple flowers that are rather larger than most others in this group. I. histrioides ‘Lady Beatrix Stanley’ has lovely blue flowers – which have yellow marking in the centre of the petals – carried on a short stem. Unlike some of the other early irises, all

I. histrioides flower strongly year after year.

I. unguicularis has delicate violet- blue flowers about 20cm (8in) high and an untidy sprawl of foliage which should not be cut back but allowed to die back slowly. They’re often planted in a border but as well as good drainage, like all these bulbs they do need exposure to summer sun – preferably hot sun – if they’re to flower well next year. ‘Mary Barnard’ is a rich shade of mauve; ‘Alba’ is white and rather late flowering.

Monty with his Iris reticulata ‘Harmony’