The Stars of the Onion Family
by Sally Gregson

They say that every part of a pig is useful except its squeak. The same could almost be said about an onion. The bulb, the leaves, and the flower are all edible and extremely decorative. The roots less so, but even they can be added to the compost heap.

Onions and garlic are so familiar that it’s easy to overlook some of the different varieties available from specialist growers of seed and sets. Elephant garlic produces huge cloves that are mild and sweet enough to pickle, and the leaves can be chopped into stir-fries. Mauve and white chive flowers are pretty and tasty added to new potatoes and tossed in olive oil. And the broad, bright green leaves of our native ramsons, or ‘wild garlic’, are the latest foodie craze to hit the trendy restaurants.

Leeks are a fine winter staple for soups and sauces, but leave them in the ground until spring and they explode into big, beautiful, starry flowers. As vegetables they would be definitely past their use-by date, but if you allowed the flowers to set seed you would have enough to sow the next crop.

Those flowers are pretty enough for any garden border, but leeks are biennials so they would need to be replaced. Alliums, to give them the correct botanical name, however, are long-lasting bulbous perennials and, given a sunny position, they will return each year. Confusingly, domestic onions require a rich, fertile soil to plump up the bulbs and increase the juiciness of leeks, whereas ornamental alliums flower much better in a poorer, well-drained soil.

One of the best new introductions in the past decade has been Allium ‘Purple Sensation’. In early summer it pushes up large fat buds on strong 1m (3ft) stems that open into violet-purple spheres the size of tennis balls. A haze of hardy white geraniums accented by its dark globes is a modern classic planting that wows the Chelsea crowds every May. As the purple petals fade, the heads become a sinister dark green: they would combine rather moodily with bronze fennel and set off the apricot flowers of Rosa ‘Buff Beauty’ well.

A few weeks later A. christophii produces crystalline lavender spheres the size of footballs. In the Rose Garden at Sissinghurst their giant heads rest on the paths beneath the ‘old roses’ in the company of spiky iris leaves and feathery columbines. Vita Sackville-West wrote that this planting ‘achieves serenity without being sweet or banal’.

Although Allium schubertii can be a little more difficult to flower successfully, its remarkable flowers seem to explode like a star-burst in the border. Give each plant a sunny spot and its own space: keep its neighbours at bay.

If your garden is not quite sunny and well-drained enough for the classic alliums, the tongue-twisting Nectaroscordum siculum subsp. bulgaricum is much more tolerant and equally striking. It has buff-maroon flowers that hang like bells around the head on 1m (3ft) stems. Then, once the flowers have been pollinated, they stand erect, like fairy-castle turrets with conical roofs, until they drop their seeds in late summer.

Over the past few years the increasing popularity of alliums has encouraged the plant breeders to produce some spectacular hybrids. Allium ‘Globemaster’ combines the flower size of A. christophii with the density of A. ‘Purple Sensation’. Although the colour is not as dark, the large heads are a deep lilac on stout stems up to 1.5m (5ft) tall. And new this year is A. ‘Silverspring’ whose globular white flowers on 70 to 90cm (2 to 3ft) stems, have violet-pink centres. It’s a pretty combination that should win a few more gold medals at Chelsea.

How to grow alliums

• Plant the bulbs in autumn in a sunny, well-drained position at least twice their own depth.
• Protect the emerging shoots from slugs and snails.
• Do not allow the heads to set seed unless you want more species alliums. The named varieties will not ‘come true’ from seed.