Overview

Iris sibirica 'Emperor' 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. It typically grows around 0.6 m tall and 0.3 m wide. Iris sibirica 'Emperor' 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. Suggested uses include borders, cut flowers and water margins. It is native to Europe and Central Asia.

About

Iris sibirica 'Emperor' is a clump-forming, upright perennial in the iris family grown for its tall flowering stems and grass-like leaves. It reaches about 0.6 m high with a 0.3 m spread and carries sword-shaped foliage that is often glaucous. Flowering in the UK runs from May to July. It suits sunny or lightly shaded, south- or west-facing positions and tolerates exposed or sheltered sites.

Wikipedia contributors, CC BY-SA 4.0 — Iris sibirica

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 clump-forming member of Iridaceae native to Europe and Central Asia, Iris sibirica 'Emperor' produces upright stems above a tussock of sword-shaped leaves and flowers in the UK from May to July. The foliage is often glaucous, giving a blue‑green cast to border plantings, and the cultivar forms a neat clump to approximately 0.6 m tall by 0.3 m across. Plant in full sun where possible, though some plants will tolerate light afternoon shade on a south- or west-facing aspect. Soil should be neutral to slightly alkaline; while the genus will grow in loam, chalk or sand, Siberian irises particularly appreciate soil that retains some moisture rather than running bone‑dry. They are rated H5–H7 for UK hardiness — hardy to fully hardy — and correspond broadly to USDA zones 3–9, so they will survive normal winter conditions across most of Britain when sited sensibly. Use Iris sibirica 'Emperor' in mixed herbaceous borders, at the edges of water margins where soil stays fresher, or lift stems for cutting. The compact 0.3 m spread makes it suitable for tighter border fronts or in groups for a low meadow effect, and stems make useful material for summer bouquets.

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 sibirica 'Emperor' size, habit and characteristics

Plant type

Perennial

Habit

Clump-forming, upright

Foliage

Deciduous or evergreen; sword-shaped to grassy, often glaucous

Height

0.6 m

Spread

0.3 m

Suggested uses

Borders, cut flowers, water margins

Native to

Europe, Central Asia

Care notes

Pruning and caring for Iris sibirica 'Emperor'

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

More in the Iris genus

• 
  Iris 'Antigone' (TB)
• 
  Iris 'Dauntless' (TB)
• 
  Iris 'Dipped in Dots' (TB)
• Iris 'Ablaze' (MDB)
• Iris 'After the Storm' (TB)
• Iris 'Aldo Ratti' (TB)
• Iris 'Alene's New Love' (SDB)iris 'Alene's New Love'
• Iris 'Alpine Lake' (MDB)