Iris unguicularis – The Algerian Iris.
This beautiful, winter flowering iris used to be called Iris stylosa; sweet sounding and easy to remember. Easy to grow too, just plant it at the base of a dry sunny wall with no added compost, and it will thrive. It seems to love poor stony soil which is no surprise when you look at its natural habitat.
For most of the year you wouldn’t give it a second glance … a scruffy collection of strap shaped, dull green leaves which often as not are brown at the tips; and horror of horrors, it is a five star hotel for snails and slugs. So sometime during the summer I go through my clump, teasing out and removing all unsightly dead leaves, dead snail shells, and generally clearing away the debris. I also shorten the leaves by half as this improves its general appearance and allows the sun to bake the rhizomes.
Then, at any time between November and March, and usually between periods of frost, the delicate lavender blue flowers emerge as if by magic. If you pick them in bud, they will unfurl indoors and delight you for that day.
It could be that you don’t have a sunny, south facing wall, in which case try Iris lazica which is very similar but flowers happily in semi shade in early spring.