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Bulbs

Allium triquetrum

three-cornered garlic

A bulbous plant with a triangular stalk up to 40cm tall and star-shaped flowers, petals each with a single green vein, produced from April to June. This attractive but rather weedy onion, native to southern Europe is occasionally cultivated intentionally but invariably becomes a nuisance, as it spreads freely by both bulbils and seeds

Other common names

three-cornered leek
triquetrous leek

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Ultimate height

0.1–0.5 metres

Time to ultimate height

2–5 years

Ultimate spread

0.1–0.5 metres

Chalk

Clay

Loam

Sand

Moisture

Moist but well–drained

pH

Acid, Alkaline, Neutral

	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Full sun
Partial shade

Aspect

East–facing or 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)

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

This plant is listed on Schedule 9 of the UK Wildlife & Countryside Act as an invasive non-native species. Although not banned from sale, it is an offence to plant or cause these to grow in the wild IN ENGLAND WALES, NORTHERN IRELAND and the REPUBLIC OF IRELAND. Gardeners possessing them should undertake measures to control them. See RHS advice on invasive non-native species for further information

Propagation

Please see cultivation notes

Suggested planting locations and garden types

Pests

Generally pest-free

Diseases

Generally disease-free

Get involved

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