Iris sibirica 'Caesar's Brother' (Siberian iris) — Clump-forming, upright

Overview

Iris sibirica 'Caesar's Brother' 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 'Caesar's Brother' 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 gardens. It is native to Europe and Central Asia.

About

Iris sibirica 'Caesar's Brother' is a clump-forming, upright Siberian iris reaching about 0.6 m and forming a 0.3 m clump. It carries sword-shaped to grassy leaves that are often glaucous and produces flowering stems in early summer. Plant it where stems can be seen and cut for floral use between May and July.

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 member of the Iridaceae native to Europe and Central Asia, Iris sibirica 'Caesar's Brother' is a rhizomatous perennial with an upright, clump-forming habit. It suits temperate gardens and is hardy in the UK from H5 to H7 — in plain terms, hardy to fully hardy across most parts of Britain and adaptable to USDA zones 3–9. Choose a sunny position, although some plants will tolerate partial shade. The cultivar prefers neutral to slightly alkaline soils and will grow in loam, chalk or sand; unlike bearded irises, Siberian types appreciate a soil that remains reliably moist at root level rather than sharply drained conditions. South or west facing sites give the best flower display. Exposure can be either sheltered or exposed. Use it in mixed borders where 0.6 m high flowering stems can add vertical interest, at the edge of water features where moisture is available, or as reliable cut flowers for summer vases. The plant's modest spread makes it straightforward to fit into perennial schemes without overwhelming neighbours. Flowers appear from May to July, supplying stems for cutting during the height of summer.

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 'Caesar's Brother' 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 gardens
Native to: Europe, Central Asia

Care notes

Pruning and caring for Iris sibirica 'Caesar's Brother'

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 sibirica 'Caesar's Brother'?

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 sibirica 'Caesar's Brother'?

Iris sibirica 'Caesar's Brother' prefers full sun; some tolerate partial shade. It suits exposed or sheltered positions.

What soil does Iris sibirica 'Caesar's Brother' need?

Iris sibirica 'Caesar's Brother' 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 sibirica 'Caesar's Brother'?

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.

How big does Iris sibirica 'Caesar's Brother' grow?

Iris sibirica 'Caesar's Brother' reaches a height of 0.6 m and a spread of 0.3 m.

Is Iris sibirica 'Caesar's Brother' hardy in the UK?

Iris sibirica 'Caesar's Brother' 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 sibirica 'Caesar's Brother'?

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 →