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Herbaceous PerennialHerbs - Culinary

Allium porrum 'Below Zero'

leek 'Below Zero'

A vigorous, cold tolerant leek with white stems and dark leaves to a height of 45cm, stands well over a long period without bolting. Tolerates extreme cold well and is resistant to rust. Leeks are herbaceous perennials usually grown as annual vegetables, with upright stems which can be blanched white, and green or blue-green leaves about 30-50cm long; plants may flower by bolting in their first year, or the following year if left overwinter, with stems up to 1.5m high topped by rounded flowerheads 5-9cm across of hundreds of star-like pale pink to white flowers which are visited by bees, in summer.

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Ultimate height

0.1–0.5 metres

Time to ultimate height

1–2 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

Exposed or 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: Evergreen
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: Accepted

How to grow

Cultivation

Sow seed, under cover in late winter or early spring or outside in late spring, about 1cm deep in moist but well-drained soil that is rich in organic matter, preferably in full sun though they will tolerate partial shade; thin seedlings to 15cm apart, or, to get the classic white stems, lift and re-plant seedlings from spring to early summer in holes 15cm deep at 15cm spacings, and harvest from late summer or early autumn to winter; for more advice, see leeks cultivation

Propagation

Propagate by seed. See sowing vegetable seeds

Suggested planting locations and garden types

Pruning

No pruning required

Pests

May be susceptible to slugs and snails, leek moth, onion fly and onion thrips

Diseases

May be susceptible to leek rust, onion white rot, downy mildews, foot and root rots, fungal leaf spots, and smuts; Below Zero is said to be resistant to rust

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