Iris spuria var. notha (Blue Iris) — Clump-forming, upright

Overview

Iris spuria var. notha 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 spuria var. notha 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.

About

Iris spuria var. notha is a clump-forming, upright perennial in the iris family with sword-shaped, often glaucous leaves and summer flowering from May to July. It suits open, sunlit positions but will tolerate some light shade. The plant prefers neutral to slightly alkaline, sharply drained soils such as loam, chalk or sand. It is winter-hardy across much of the UK.

Wikipedia contributors, CC BY-SA 4.0 — Iris spuria

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 spuria var. notha is a perennial iris within Iridaceae, originating from regions of Europe, Asia and Africa, and producing its flowers in the UK between May and July. Its habit is an upright, clump-forming perennial with elongated, sword-shaped leaves that often show a glaucous bloom, giving the clump a clear architectural outline through the growing season. For best results place the plant in full sun; it will tolerate some partial shade. Soils that suit it include loam, chalk or sand with neutral to slightly alkaline pH, and a preference for good drainage — note that sharply drained conditions are recommended for similar iris types. Aspect is important: a south- or west-facing spot encourages reliable flowering, and the species will cope equally well on exposed sites or in more sheltered corners. Hardiness is rated H5–H7, meaning it is winter-hardy to fully hardy across most UK regions. Use Iris spuria var. notha where upright form and summer blooms are required: mixed or perennial borders, gravel beds and exposed sites are appropriate. The erect clumps and glaucous, sword-shaped leaves remain structurally present once the May–July flowers have finished, giving clear vertical form through 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 spuria var. notha size, habit and characteristics

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

Care notes

Pruning and caring for Iris spuria var. notha

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 spuria var. notha?

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 spuria var. notha?

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

What soil does Iris spuria var. notha need?

Iris spuria var. notha 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 spuria var. notha?

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 spuria var. notha hardy in the UK?

Iris spuria var. notha 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 spuria var. notha?

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 →