Overview

Iris unguicularis 'Walter Butt' 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 0.3 metres tall. Iris unguicularis 'Walter Butt' 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 Algeria, Greece, Turkey, Western Syria and Tunisia.

About

Iris unguicularis 'Walter Butt' is a clump-forming, upright perennial in the iris family, notable for its fragrant pale lilac to purple flowers. Plants reach about 0.3 metres and carry sword-shaped to grassy, often glaucous leaves that may be deciduous or evergreen. In the UK it flowers from May to July. The plant is harmful if eaten, so wear gloves and other protective equipment when handling.

Wikipedia contributors, CC BY-SA 4.0 — Iris unguicularis

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 unguicularis 'Walter Butt' belongs to the Iridaceae and originates from parts of the Mediterranean, including Algeria, Greece, Turkey, Western Syria and Tunisia. Individual plants form compact upright clumps to roughly 0.3 metres and produce fragrant pale lilac to purple flowers with a yellow central band; flowering in the UK occurs from May to July. Give the cultivar a sunny, south- or west-facing position; it will tolerate some light shade but performs best in full sun. Soil should be well drained — loam, chalk or sandy types suit it — with a neutral to slightly alkaline pH. The species is classed H5–H7, meaning it ranges from hardy to fully hardy across most of the UK; the USDA range is 3–9. Exposure may be sheltered or exposed without harm, provided drainage is good. Use 'Walter Butt' at the front of a sunny border, in a gravel or alkaline bed, or in a container placed by a path or patio where the fragrance can be appreciated. At about 0.3 metres high the flowers sit close to eye level, making them easy to inspect. Take care with pruning and division: the plant is harmful if eaten and can irritate skin, so follow safety guidance (for pets see the HTA guide to potentially harmful plants).

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 unguicularis 'Walter Butt' size, habit and characteristics

Plant type

Perennial

Habit

Clump-forming, upright

Foliage

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

Height

0.3 metres

Native to

Algeria, Greece, Turkey, Western Syria, Tunisia

Fragrance

Flower

Toxicity

Harmful if eaten. Wear gloves and other protective equipment when handling. Pets: Harmful if eaten. For further information and contact numbers regarding pets, see the HTA guide to potentially harmful plants

Care notes

Pruning and caring for Iris unguicularis 'Walter Butt'

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)