Iris 'Monspur' 'Cambridge Blue' — Clump-forming, upright

Overview

Iris 'Monspur' 'Cambridge Blue' 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 'Monspur' 'Cambridge Blue' 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, rock gardens, cottage gardens and cut flowers.

About

Iris 'Monspur' 'Cambridge Blue' is a clump-forming, upright perennial in the Iridaceae with sword-shaped foliage that is often glaucous. It flowers in the UK from May to July. Plant it in a sunny, south- or west-facing spot where it will receive full sun or light afternoon shade. It is hardy to fully hardy in UK gardens and works well for borders, rock gardens, cottage plots and cutting.

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 cultivated member of the genus Iris, Iris 'Monspur' 'Cambridge Blue' grows as an upright, clump-forming perennial with sword-shaped to grassy leaves that are often glaucous and may be deciduous or evergreen. The plant belongs to the iris family, Iridaceae, and suits gardeners looking for a spring–early summer flowering perennial. Flowering occurs in the UK from May to July. Give it a sunny aspect—south or west facing is ideal—and allow for some tolerance of light partial shade. It thrives in loam, chalk or sandy soils with a neutral to slightly alkaline reaction; good drainage is important for many irises. For bearded types provide sharply drained soil, whereas Siberian and Japanese irises favour more moisture-retentive conditions. The cultivar is rated H5–H7, meaning it is hardy to fully hardy in the UK; on a wider scale it corresponds to USDA zones 3–9. Siting options include mixed herbaceous borders, rock gardens and cottage-style plantings, and stems are suitable for cutting. Position plants where winter wet is avoided and you will get reliable flowering through the May to July season when stems are at their best for vases.

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 'Monspur' 'Cambridge Blue' size, habit and characteristics

Plant type: Perennial
Habit: Clump-forming, upright
Foliage: Deciduous or evergreen; sword-shaped to grassy, often glaucous
Suggested uses: Borders, rock gardens, cottage gardens, cut flowers

Care notes

Pruning and caring for Iris 'Monspur' 'Cambridge Blue'

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 'Monspur' 'Cambridge Blue'?

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 'Monspur' 'Cambridge Blue'?

Iris 'Monspur' 'Cambridge Blue' prefers full sun; some tolerate partial shade. It suits exposed or sheltered positions.

What soil does Iris 'Monspur' 'Cambridge Blue' need?

Iris 'Monspur' 'Cambridge Blue' 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 'Monspur' 'Cambridge Blue'?

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 'Monspur' 'Cambridge Blue' hardy in the UK?

Iris 'Monspur' 'Cambridge Blue' 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 'Monspur' 'Cambridge Blue'?

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

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