Overview

Iris stolonifera 'Zwanenburg Beauty' 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 stolonifera 'Zwanenburg Beauty' 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 Mountains of Turkestan, between Tajikistan and Uzbekistan and Afghanistan.

About

Iris stolonifera 'Zwanenburg Beauty' is a clump-forming, upright perennial in the iris family, valued for its sword-shaped, often glaucous leaves and late-spring flowers. It originates from the mountains of Turkestan between Tajikistan, Uzbekistan and Afghanistan. Flowers appear from May to July. The plant is suitable for a south- or west-facing site in well-drained neutral to slightly alkaline soils.

Wikipedia contributors, CC BY-SA 4.0 — Iris stolonifera

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 stolonifera 'Zwanenburg Beauty' is a perennial iris with an upright, clump-forming habit and glaucous, sword-shaped foliage. It comes from the mountains of Turkestan in central Asia, and is grown for its seasonal display in late spring and early summer, flowering from May to July. As a member of Iridaceae it favours open, sunny conditions but some plants will tolerate a little light afternoon shade. Plant it in loam, chalk or sandy soils with a neutral to slightly alkaline pH and good drainage; the species does not suit waterlogged conditions. Give a south- or west-facing aspect where the soil can dry between wetter spells, and avoid overly shaded hollows. Hardiness is H5–H7 (hardy to fully hardy) in the UK and roughly equivalent to USDA zones 3–9, so it withstands typical British winters across most regions. Use Iris stolonifera 'Zwanenburg Beauty' where its upright form and blue-grey leaves can be seen — beside gravel paths, on a dry bank or at the front of a mixed perennial border. It will perform where exposure ranges from sheltered to fairly exposed, provided the soil drains freely. Expect flowering in May to July and allow room for the clump-forming habit to mature.

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 stolonifera 'Zwanenburg Beauty' size, habit and characteristics

Plant type

Perennial

Habit

Clump-forming, upright

Foliage

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

Native to

Mountains of Turkestan, between Tajikistan, Uzbekistan and Afghanistan

Care notes

Pruning and caring for Iris stolonifera 'Zwanenburg Beauty'

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)