Iris tectorum 'Lilacina' (Roof Iris) — Clump-forming, upright

Overview

Iris tectorum 'Lilacina' 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 m tall. Iris tectorum 'Lilacina' 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 China.

About

Iris tectorum 'Lilacina' is a clump-forming, upright perennial with blue-lilac flowers that appear in May to July. It grows to about 0.3 m, producing sword-shaped, often glaucous leaves that form low basal fans. Native to China, it suits sunny, neutral to slightly alkaline sites with good drainage.

Wikipedia contributors, CC BY-SA 4.0 — Iris tectorum

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 tectorum 'Lilacina' is a compact, rhizomatous perennial from China, grown for its blue‑lilac flowers in early summer. Flowering occurs from May to July, when short stems rise above the basal fans of sword-shaped, often glaucous leaves. Plants reach roughly 0.3 m and form neat clumps rather than tall tussocks. Position the plant in full sun on a south- or west-facing aspect; it will tolerate some light shade but flowers best with more sun. Use loam, chalk or sand-based soil on a neutral to slightly alkaline pH and ensure the planting site drains freely. While general irrigation should avoid waterlogging, note that some iris groups prefer moisture-retentive ground—observe the plant and adapt watering to the bed conditions. Iris tectorum 'Lilacina' carries a UK hardiness rating of H5–H7, meaning it is hardy to fully hardy across most British gardens, and corresponds to USDA zones 3–9. Its low, upright habit and semi-compact height make it suitable for the front of a border, edging a sunny path or planting beneath open shrubs where it receives good light and air movement. Allow small clumps room to spread so the characteristic glaucous foliage remains visible once flowers fade.

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 tectorum 'Lilacina' size, habit and characteristics

Plant type: Perennial
Habit: Clump-forming, upright
Foliage: Deciduous or evergreen; sword-shaped to grassy, often glaucous
Height: 0.3 m
Native to: China

Care notes

Pruning and caring for Iris tectorum 'Lilacina'

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 tectorum 'Lilacina'?

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 tectorum 'Lilacina'?

Iris tectorum 'Lilacina' prefers full sun; some tolerate partial shade. It suits exposed or sheltered positions.

What soil does Iris tectorum 'Lilacina' need?

Iris tectorum 'Lilacina' 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 tectorum 'Lilacina'?

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.

How big does Iris tectorum 'Lilacina' grow?

Iris tectorum 'Lilacina' reaches a height of 0.3 m.

Is Iris tectorum 'Lilacina' hardy in the UK?

Iris tectorum 'Lilacina' 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 tectorum 'Lilacina'?

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 →