HOW TO GROW

Hailing from the magnesium-rich limestone of the Dolomites, the rhizomatous iris needs plenty of sunshine and free drainage. Though adaptable as garden plants, it is worth giving them a position in full sun where they will not be

overshadowed. They prefer not to have companions so that they can harvest all the light, and are best grown alone to the front of a bed where they can bask or, as I grow them, at the foot of a sunny wall.

Their early growth and rush towards May flowering is made possible by the energy from the previous summer that is stored in the root. During flowering however, their whole root system dies and the plants go into a period of semidormancy in June and July after setting seed. The majority of the foliage at this point will wither and can be pulled away to allow good air circulation and light to fall on the rhizome. It is at this point and on a five to six year rotation that they need to be split. A single rhizome and fan of foliage should be taken from the outside of the clump and replanted with the rhizome at soil level, not covered, and the foliage

angled like a deck chair with the body of the rhizome in the sun.

Sarah Cook moves her whole collection after two divisions, keeping them for no more than ten years in one piece of ground. Left for longer in one place and they will begin to dwindle as they deplete the micronutrients that are essential to the effort they put into flowering.

For best results feed lightly (around 60g for every square metre) with a general purpose fertiliser, such as Vitax Q4, twice in a season. First in March to stimulate flowers and then in July to encourage the root growth.