Allium rosenbachianum Regel

RHS Plant Profile

showy Persian onion

Synonyms

Allium rosenbachianum subsp. rosenbachianum
Allium angustipetalum

Bulbs

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Bulbous perennial about 1m tall, with strap-shaped, grey-green basal leaves to 30cm long. In early summer, the tall flowering stems carry large, globular heads of tightly packed, star-shaped, reddish-purple flowers to 10cm across, with prominent violet stamens

Position

Full sun

Soil Types

Chalk, Loam, Sand

Max Height

0.5-1 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity: 1–2 years
Max Spread: 0.1-0.5 metres
Max Height: 0.5-1 metres

Growing Conditions

Chalk Loam Sand

Moisture: Moist but well–drained or Well–drained
pH: Acid or Alkaline or Neutral

Position

Full sun

Aspect: South–facing or West–facing
Exposure: Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

H1A: under glass all year (>15C)
H1B: can be grown outside in the summer (10 - 15)
H1C: can be grown outside in the summer (5 - 10)
H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
H4: hardy through most of the UK (-10 to -5)
H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
H6: hardy in all of UK and northern Europe (-20 to -15)
H7: hardy in the severest European continental climates (< -20): H5

Colour & Scent

Fragrance Foliage

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Amaryllidaceae
Native to GB/Ireland: No
Foliage: Deciduous
Habit: Clump forming
Genus: Allium are bulbous herbaceous perennials with a strong onion or garlic scent, linear, strap-shaped or cylindrical basal leaves and star-shaped or bell-shaped flowers in an umbel on a leafless stem
Name Status: Correct

How to Grow

Cultivation

Grow in full sun and fertile well-drained soil. It is best to grow in containers where garden soil is heavy clay and prone to saturation over winter. See allium cultivation

Propagation

Propagate by seed when just ripe or in spring; or propagate by offsets which can be carefully detached by lifting the bulb after flowering has finished. See bulb propagation

Suggested planting locations and garden types

Cottage and informal garden
City and courtyard gardens
Gravel garden
Patio and container plants
Wildlife gardens
Cut flowers
Flower borders and beds

Pruning

No pruning required, other than to remove old flowered stems and foliage

Pests

May be susceptible to allium leaf miner and onion fly

Diseases

May be susceptible to onion white rot and onion downy mildew