Overview

Iris sibirica 'White Swirl' 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. It typically grows around 0.6 m tall and 0.3 m wide. Iris sibirica 'White Swirl' 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, water gardens and cut flowers. It is native to Europe and Central Asia.

About

Iris sibirica 'White Swirl' is a clump-forming, upright perennial in the iris family that produces flowers from May to July. It reaches about 0.6 m high with a 0.3 m spread and carries sword-shaped, often glaucous leaves. Suited to neutral to slightly alkaline soils, it favours moisture-retentive ground among loam, chalk or sand. Plants perform in full sun and will tolerate some light afternoon shade.

Wikipedia contributors, CC BY-SA 4.0 — Iris sibirica

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 member of Iridaceae native to Europe and Central Asia, Iris sibirica 'White Swirl' forms dense clumps of grassy, sword-like foliage and puts up flowering stems in late spring and early summer. Expect plants to grow to roughly 0.6 m tall with a 0.3 m spread, making them a mid-height structural element in a herbaceous border. Place the iris in full sun or a site with some afternoon shade on a south- or west-facing aspect. It prefers neutral to slightly alkaline soils — loam, chalk or sharp sand — but as a Siberian kind benefits from soil that holds moisture while still draining; avoid permanently waterlogged spots. The clump is rated H5–H7, so it is hardy through most UK winters and will tolerate exposed as well as sheltered positions. Use White Swirl in mixed borders, along the edge of a pond or in a dedicated water garden where the soil stays reliably moist, and cut stems for flower arranging during its May to July season. Divide congested clumps after flowering if flowering thins, and lift chosen rhizomes to refresh plantings.

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 sibirica 'White Swirl' size, habit and characteristics

Plant type

Perennial

Habit

Clump-forming, upright

Foliage

Deciduous or evergreen; sword-shaped to grassy, often glaucous

Height

0.6 m

Spread

0.3 m

Suggested uses

Borders, water gardens, cut flowers

Native to

Europe, Central Asia

Care notes

Pruning and caring for Iris sibirica 'White Swirl'

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

More in the Iris genus

• 
  Iris 'Antigone' (TB)
• 
  Iris 'Dauntless' (TB)
• 
  Iris 'Dipped in Dots' (TB)
• Iris 'Ablaze' (MDB)
• Iris 'After the Storm' (TB)
• Iris 'Aldo Ratti' (TB)
• Iris 'Alene's New Love' (SDB)iris 'Alene's New Love'
• Iris 'Alpine Lake' (MDB)