Iris monnieri — Clump-forming, upright

Overview

Iris monnieri 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 monnieri 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 China.

About

Iris monnieri is a clump-forming, upright perennial iris from China with sword-shaped to grassy leaves that are often glaucous. Flowering occurs from May to July on erect stems above the foliage. It suits full sun though some plants will tolerate a little light shade. Plants are winter-hardy across much of the UK.

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

Iris monnieri is a perennial member of the Iridaceae, native to China, that forms upright clumps of sword-shaped to grassy leaves, often with a bluish–grey (glaucous) bloom. Flowering takes place from May to July on erect stems that sit above the foliage, providing a defined seasonal display. Specific flower colour varies by selection and is not uniform across the species. Place Iris monnieri in full sun for best flowering, allowing some tolerance of light, partial shade for less exposed sites. It prefers neutral to slightly alkaline soils such as loam, chalk or sand and performs best in a well-drained planting medium; note that other iris groups (for example Siberian and Japanese irises) typically need more moisture-retentive ground. Aim for a south- or west-facing position but the species will tolerate exposed or sheltered sites. Hardiness runs H5–H7, meaning plants are hardy to fully hardy across most UK gardens. Use it where upright, structural foliage is required at the front or middle of a sunny herbaceous border or in well-drained gravel and chalk beds; the glaucous leaves hold their shape through the season and the May to July flowering period is the best time to judge its contribution to a border scheme.

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 monnieri size, habit and characteristics

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

Care notes

Pruning and caring for Iris monnieri

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 monnieri?

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 monnieri?

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

What soil does Iris monnieri need?

Iris monnieri 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 monnieri?

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 monnieri hardy in the UK?

Iris monnieri 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 monnieri?

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 →