Iris laevigata 'Alba' (Japanese Iris) — Clump-forming, upright

Overview

Iris laevigata 'Alba' is a clump-forming, upright perennial in the genus Iris, part of the Iridaceae family, with deciduous or evergreen; sword-shaped to grassy, often glaucous foliage. Iris laevigata 'Alba' grows best in full sun; some tolerate partial shade, and tolerates loam and chalk or sand; sharply drained for bearded kinds soils and neutral to slightly alkaline pH. Its UK hardiness is rated H5–H7. It is native to Japan.

About

Iris laevigata 'Alba' is a clump-forming, upright perennial in the Iridaceae from Japan that flowers from May to July. It carries sword-shaped leaves that are often glaucous and may be deciduous or remain evergreen. Plant in a sunny site (some tolerance of light shade) with soil that holds moisture rather than dries out. Suited to south- or west-facing positions and tolerates exposed or sheltered sites.

Wikipedia contributors, CC BY-SA 4.0 — Iris laevigata

About the genus

Iris takes its name from the Greek goddess of the rainbow, and for once the naming feels entirely earned. I can't think of another genus that covers so much ground — inky purples, burnt apricots, clean whites, blues that seem lit from inside — or so many situations. There are bearded irises that want their rhizomes baked in full sun, Siberian types happy in ordinary border soil, and species that will sit contentedly at the edge of a pond. What they share is the flower: three petals standing up, three falling away, built with a kind of architectural confidence most plants never attempt. Even out of bloom the foliage earns its place — those upright fans of blue-green leaves hold a border together for months. I grow them for the fortnight in May and June when nothing else in the garden can compete, and I've made my peace with that. Some plants are for the long haul. An iris is an event.

Written by Henry

In the garden

A member of the Iris genus native to Japan, Iris laevigata 'Alba' forms upright clumps of sword-shaped foliage and produces its blooms between May and July. It sits within hardiness H5–H7, meaning it is hardy through most UK gardens and ranges from hardy to fully hardy; the USDA range is 3–9. The plant prefers a sunny aspect but will tolerate some partial shade, and performs best on south- or west-facing sites. Exposure is adaptable, coping with both exposed and sheltered positions. Soil should be neutral to slightly alkaline and able to retain moisture; while many irises need sharp drainage, Japanese types benefit from moisture-retentive loam rather than dry, free-draining situations. The listed suitable soil types include loam, chalk and sand, but give priority to soil that holds water through the growing season for this species. Position plants where roots remain evenly damp during spring and early summer for the best flower set. Use Iris laevigata 'Alba' where a moisture-retentive border is required and when a mid-to-late spring display is wanted; its clump-forming habit fills a stand of perennial planting. Expect repeated flowering stems from established clumps through the May to July window as the plants mature.

Growing conditions

Best soil and position for Iris

Sunlight: Full sun; some tolerate partial shade
Soil type: Loam, chalk or sand; sharply drained for bearded kinds
Soil pH: Neutral to slightly alkaline
Soil moisture: Well drained; Siberian and Japanese kinds need moisture-retentive soil
Aspect: South or west facing
Exposure: Exposed or sheltered
UK hardiness: H5–H7

Plant details

Iris laevigata 'Alba' size, habit and characteristics

Plant type: Perennial
Habit: Clump-forming, upright
Foliage: Deciduous or evergreen; sword-shaped to grassy, often glaucous
Native to: Japan

Care notes

Pruning and caring for Iris laevigata 'Alba'

Cultivation: Plant bearded irises with the top of the rhizome exposed so it can bake in summer sun; beardless kinds sit just below the surface in richer, damper ground. Feed with a low-nitrogen fertiliser after flowering and keep the rhizomes clear of mulch and encroaching neighbours.
Pruning: Remove spent flower stems at the base. Trim the outer leaves back by about half in late autumn to reduce overwintering fungal spores, leaving the central fan intact.
Propagation: Divide rhizomes six to eight weeks after flowering, discarding the old woody centre and replanting vigorous outer sections. Species come from seed, but named cultivars will not come true.
Pest resistance: Generally trouble-free, though iris sawfly and slugs damage foliage and thrips can disfigure buds.
Disease resistance: Prone to leaf spot, and to rhizome rot wherever drainage is poor or planting too deep.

Frequently asked questions

How do I grow Iris laevigata 'Alba'?

Plant bearded irises with the top of the rhizome exposed so it can bake in summer sun; beardless kinds sit just below the surface in richer, damper ground. Feed with a low-nitrogen fertiliser after flowering and keep the rhizomes clear of mulch and encroaching neighbours.

Where is the best place to plant Iris laevigata 'Alba'?

Iris laevigata 'Alba' prefers full sun; some tolerate partial shade. It suits exposed or sheltered positions.

What soil does Iris laevigata 'Alba' need?

Iris laevigata 'Alba' grows best in loam and chalk or sand; sharply drained for bearded kinds soil. It prefers neutral to slightly alkaline soil. Aim for soil that stays well drained; siberian and japanese kinds need moisture-retentive soil.

How do I prune Iris laevigata 'Alba'?

Remove spent flower stems at the base. Trim the outer leaves back by about half in late autumn to reduce overwintering fungal spores, leaving the central fan intact.

Is Iris laevigata 'Alba' hardy in the UK?

Iris laevigata 'Alba' has an RHS hardiness rating of H5, meaning it is hardy in most of the UK, tolerating -15 to -10°C.

How do I propagate Iris laevigata 'Alba'?

Divide rhizomes six to eight weeks after flowering, discarding the old woody centre and replanting vigorous outer sections. Species come from seed, but named cultivars will not come true.

More in the Iris genus

Browse all Iris →