Iris korolkowi 'Concolor' — Clump-forming, upright

Overview

Iris korolkowi 'Concolor' 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 korolkowi 'Concolor' 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 Central Asia.

About

Iris korolkowi 'Concolor' is a clump-forming, upright perennial iris from Central Asia with sword-shaped, often glaucous leaves. It produces its flowers from May to July. The plant favours full sun or light afternoon shade and prefers neutral to slightly alkaline, well-drained soils. It is winter-hardy across most of the UK (H5–H7).

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 compact, clump-forming iris, Iris korolkowi 'Concolor' originates in Central Asia and carries the typical sword-shaped foliage of the genus. The leaves are often glaucous and may be deciduous or persist through winter depending on site conditions. Flowering runs from May to July, when the blooms sit above the foliage. Plant it in a sunny spot, ideally south- or west-facing; some plants will tolerate a little light shade but bloom best in full sun. Soils of loam, chalk or sand suit it provided they drain freely; aim for neutral to slightly alkaline pH. Give well-drained conditions year-round and avoid waterlogging in winter. The cultivar is rated H5–H7 (hardy to fully hardy) and corresponds to USDA zones 3–9, so it withstands cold winters across most of the UK. Use Iris korolkowi 'Concolor' where its upright clumps can be seen—at the front of a sunny border, in a gravel bed on a southern slope, or on a sheltered bank with good drainage. Planting with other sun-loving perennials that prefer neutral to alkaline soil keeps cultural needs aligned. Expect flowering between May and July, when upright clumps lift the flowers above the glaucous sword-shaped leaves.

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 korolkowi 'Concolor' size, habit and characteristics

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

Care notes

Pruning and caring for Iris korolkowi 'Concolor'

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 korolkowi 'Concolor'?

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 korolkowi 'Concolor'?

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

What soil does Iris korolkowi 'Concolor' need?

Iris korolkowi 'Concolor' 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 korolkowi 'Concolor'?

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 korolkowi 'Concolor' hardy in the UK?

Iris korolkowi 'Concolor' 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 korolkowi 'Concolor'?

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 →