Iris xiphioides (Iris) — Clump-forming, upright

Overview

Iris xiphioides 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 xiphioides 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 Spain.

About

Iris xiphioides is a clump-forming, upright perennial in the iris family, noted for its sword-shaped, often glaucous leaves. It flowers from May to July. It prefers full sun and will tolerate some light shade, growing in neutral to slightly alkaline loam, chalk or sand with good drainage; bearded types favour sharply drained positions. Hardy from H5 to H7, it suits south- or west-facing exposures, whether exposed or sheltered.

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 Iridaceae native to Spain, Iris xiphioides produces an upright clump of sword-like foliage and a succession of iris blooms from May to July. As a perennial it returns year after year and is typically grown for its architectural leaves as well as its flowering season. Place it in a sunny spot, allowing for some tolerance of light afternoon shade. It favours neutral to slightly alkaline soils and will grow in loam, chalk or sand; maintain good drainage, and use sharply drained pockets where bearded forms are being cultivated. Soil moisture should be reliably free-draining rather than waterlogged. South- or west-facing positions suit the plant’s flowering habit, and it copes equally well in exposed or sheltered situations. Hardiness in the UK ranges from H5 to H7, meaning it is hardy through most gardens and will also perform across USDA zones 3–9. Use Iris xiphioides in sunny mixed borders or gravel beds where sharply drained soil is available; its vertical leaf fans give structure outside the flowering period. The glaucous, sword-shaped leaves, whether deciduous or evergreen, remain a characteristic feature after the flowers have finished.

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 xiphioides size, habit and characteristics

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

Care notes

Pruning and caring for Iris xiphioides

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 xiphioides?

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 xiphioides?

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

What soil does Iris xiphioides need?

Iris xiphioides 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 xiphioides?

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 xiphioides hardy in the UK?

Iris xiphioides 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 xiphioides?

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 →