In May and June the Main Borders at Harlow Carr give a stunning display of different kinds of ornamental onions. Our mass plantings include: Allium ‘Mont Blanc’, A. hollandicum ‘Purple Sensation’ AGM, A. atropurpureum, A. nigrum, A. schubertii and A. cristophii. There will be thousands of blooms!
- Common name
- Star of Persia
- Height & spread
- 30-60cm (12-24in) x 15cm (6in)
- Bulbous perennial
- Fertile and well drained soil
- Full sun
- Fully hardy, but may be tender when young
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 10cm (4in) to 150cm (5ft) or more.
They are mainly from dry and mountainous areas, all from the Northern Hemisphere, and they have adapted to live in almost every plant habitat on the planet, from ice cold tundra to burning, 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 tubular based flowers are bell, star or cup shaped which are borne in spherical umbels 1cm (3/8in) to 10cm (4in) 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. The Romans are sometimes held responsible for their wide distribution by taking them wherever they went.
This bulbous perennial has ribbed grey-green strap-like leaves that emerge from the bulb and grow to 40cm (16in) long. After the leaves die back tiny pink-purple star shaped flowers appear clustered together at the top of the stalk, giving this Allium its characteristic lollipop look, which in botany is called an umbel. Flowers are 20cm (8in) across and take on a metallic colour in early summer.
Flower stalks dry well and can be used in arrangements or they can be left outside to provide winter interest as they look good covered in frost.
Contact with bulbs may irritate skin.
- 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.
- 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.
The RHS Herbaceous Plant Committee awarded Allium cristophii an Award of Garden Merit and described it as a:
"Herbaceous perennial to 60cm, with strap-shaped, slightly glaucous leaves withering by flowering time. Star-shaped, rosy-violet flowers are borne in globose heads to 20cm wide. Attractive seed-head."