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Allium sphaerocephalon

Allium sphaerocephalon

This green to purple summer-flowering ornamental onion looks great planted in combination with Nepeta 'Six Hills Giant', Centranthus ruber and Rosa 'Gertrude Jekyll' ('Ausbord') AGM. Its oval flowerheads stand about 60cm or more tall - insects love them, and they add movement and interest to borders.

 

Vital statistics

Common name
Round-headed leek
Family
Alliaceae
Height & spread
60 x 90cm (2 x 3 ft).
Form
Bulbous perennial
Soil
Fertile, well-drained soil
Aspect
Full sun
Hardiness
Fully hardy but may be tender when young

Allium

The name Allium is from the ancient name for garlic, which is part of the genus. There are estimated to be around 700 species within the genus, and many cultivars. There are perennials and biennials, ranging in height from 10 - 150cm or more.

They are mainly from dry and mountainous areas in the northern hemisphere, and they have adapted to live in almost every plant habitat on the planet, from ice cold tundra to arid deserts.

Many members of the genus give themselves away with the distinctive smell of onions when the bulb or foliage is bruised.

They have upright to spreading linear-shaped leaves. The flowers are bell, star or cup shaped and are borne in spherical umbels 1 - 10cm across.

In most species, a single bulb produces clusters of offset bulbs around it, which gradually form clumps. Taller species look good in groups in a border. The flower heads dry well.

Several species have culinary uses, including A. sativum (garlic), culinary onions, shallots and chives. The whole group was prized by the ancients as possessing medical and aphrodisiac qualities as well as flavour, and the Romans are sometimes held responsible for their wide distribution by taking them wherever they went.

Allium sphaerocephalon

This summer-flowering bulbous perennial has straight, slender stems that reach between 60 - 90cm (2 - 3 ft). Each stem is topped by a small, egg-shaped flower head, that starts off completely green before turning purple at the tip and becoming deep reddish purple. Contact with bulbs may irritate skin.

Find this drumstick allium in garden four of our Gardens Through Time. It has very slender stems, almost chive-like, with teardrop-shaped flowerheads as opposed to the usual conical sphere. They sit very well in a rose bed and also look good among vegetables in our Kitchen Garden.

Cultivation

  • Grow in fertile, well-drained soil in full sun. Plant bulbs 5-10cm (2-4in) deep in autumn.
  • Plant clump-forming species with rhizomes at or just below the soil surface in spring.
  • Alliums are susceptible to white rot, downy mildew and onion fly.

Propagation

  • Propagate by offsets, removed when dormant or by seed in spring at about 13°C (55°F). Keep moist and well ventilated, and dry progressively as foliage dies back. Prick out and pot on when dormant. Seed grown plants, however, may not come true to the parent.
  • Alternatively divide clumps of spring flowering species in summer. 

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