Plant of the month: February

Iris lazica @ Rosemoor

Iris lazica is one of the earliest irises to flower with us and we have large groups of this lovely plant, with its bright blue flowers (an unusual colour in the garden at this time of the year), growing along the front of the Visitor Centre, in Lady Anne's Garden and in many other beds throughout the garden.

Iris

This is a genus of about 300 species of upright, rhizomatous or bulbous, sometimes fleshy-rooted perennials. It was named for the Greek goddess of the rainbow and is found in a wide range of habitats in the northern hemisphere.

The leaves are sword-shaped, often arranged in fans and sometimes variegated.

The flowers have six tepals (a word used for sepals or petals when they are not easily distinguished): three usually erect standards alternating with three downward-curving falls, which may be bearded (hairs in the centre of each fall tepal), beardless or crested (a ridge on each fall tepal). They occur in all colours.

Irises have been cultivated since the reign of the Egyptian pharaoh Thutmosis I, in about 1500 BC. They are grown mainly for their distinctive flowers, which are produced in spring and summer. The taller cultivars are suitable for mixed or herbaceous borders, the smaller cultivars for rock gardens, raised beds and troughs, and water irises for the margins of pools and streams. A few that are not frost hardy need protection under glass.

Irises are divided into Rhizomatous and Bulbous groups and the former group, to which Iris lazica belongs, is subdivided into Bearded, Beardless and Crested irises.

Iris lazica

This species is a rhizomatous, beardless, Unguiculares iris. The Unguiculares irises are significantly different from the other beardless irises: they bloom from autumn to spring with only one flower per stem, they are evergreen and they develop a mass of rhizomes above the ground. Their flower colour ranges from blue, through violet and lavender-pink to white, the flowers being almost stemless with long perianth tubes.

I. lazica comes from north-eastern Turkey and Georgia. The name lazica refers to the fact that this iris was found in Lazistan on the shores of the Black Sea.

The leaves are bright green, about 30cm (12in) long and arranged in arching fans.

The flowers, borne in early spring, are scentless, 6-8cm (2.5-3in) across with lavender-blue tepals and white and yellow falls with lavender spots and veins.

Unlike other Unguiculares, I. lazica enjoys light shade and moist soil. The best place to grow it is in a sheltered spot in dappled shade, in a rock garden or up against a wall, which would provide some protection against frost, provided the soil was kept moist.

AGM

The RHS Joint Iris Committee awarded Iris lazica an Award of Garden Merit and described it as: Evergreen, rhizomatous perennial to 25cm tall, with arching glossy green leaves and deep purple or lavender-blue flowers 6-8cm wide, the base of the falls veined on a white ground.

Cultivation

Grow in moist, neutral to alkaline soil in partial shade. When planted, the rhizome should be partially exposed. Plant singly or in groups of three with the fans outermost, 15-30cm (6-12in) apart.

Feed or top-dress with a low nitrogen fertilizer when planting, in late summer or early autumn, and again in early spring.

Slugs and snails may be a problem, as may grey mould (Botryris) and thrips.

Propagation

Lift rhizomes or divide clumps, when dormant, and plant immediately in the flowering site.

Sow seed in containers in a cold frame in autumn or spring.