Iris kaempferi 'Regel' of gardens (Japanese Iris) — Clump-forming, upright

Overview

Iris kaempferi 'Regel' of gardens 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 kaempferi 'Regel' of gardens 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 Japan, China, Korea and Russia.

About

Iris kaempferi 'Regel' of gardens is an upright, clump-forming perennial iris valued for its seasonal flowers. Native to Japan, China, Korea and Russia, it bears sword-shaped to grassy leaves that are often glaucous. Flowering occurs in the UK from May to July.

Wikipedia contributors, CC BY-SA 4.0 — Iris ensata

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 kaempferi 'Regel' of gardens is a clump-forming, upright perennial in the Iridaceae with origins in Japan, China, Korea and Russia. It produces its main display in the UK flowering season of May to July, carried above sword-shaped to grassy leaves that commonly show a glaucous bloom as the clump develops. Place the plant in full sun where possible, though it will tolerate some light shade; choose a south- or west-facing spot. Soils of loam, chalk or sand suit this iris, with a neutral to slightly alkaline pH. Unlike bearded irises, Japanese types benefit from a soil that retains some moisture rather than being sharply drained. Sites may be exposed or sheltered, and the hardiness range H5–H7 means the cultivar is classed from hardy to fully hardy across most UK locations. Use Iris kaempferi 'Regel' of gardens at the rear of a mixed border or in moisture-retentive beds where its upright clumps will provide height during the May–July flowering window. The sword-shaped leaves give architectural structure outside the bloom period and tend to form steadily enlarging clumps over time.

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 kaempferi 'Regel' of gardens size, habit and characteristics

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

Care notes

Pruning and caring for Iris kaempferi 'Regel' of gardens

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 kaempferi 'Regel' of gardens?

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 kaempferi 'Regel' of gardens?

Iris kaempferi 'Regel' of gardens prefers full sun; some tolerate partial shade. It suits exposed or sheltered positions.

What soil does Iris kaempferi 'Regel' of gardens need?

Iris kaempferi 'Regel' of gardens 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 kaempferi 'Regel' of gardens?

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 kaempferi 'Regel' of gardens hardy in the UK?

Iris kaempferi 'Regel' of gardens 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 kaempferi 'Regel' of gardens?

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 →