Ornamental onions the perfect ingredient
THE purple globes of alliums are very distinctive in gardens in May and June. The perfect globe shape is not common, but very eye-catching, and the purple colour is striking. Yet alliums are relatively new in gardens, appearing for not much more than a decade now to any great extent.
Alliums are related to onions, and sometimes called ornamental onions. The cultivated onions and related leeks, chives and garlic all have round heads of flowers but they are mainly white and not as nicely structured as the species used in flower borders.
There are various kinds, the biggest is the size of a melon, but mainly they are about tennis-ball size or grapefruit size. A few species have a more tufted shape, some with yellow flowers, but the best effects are created by those with a rounded shape composed of tiny star flowers. Alliums are hardy and can be left in the ground year after year. They are long-lasting in the right conditions but often get attacked by snails, damaging the leaves and reducing the plant's ability to form flowers.
The large species Allium schubertii has huge flower heads of starry pale purple flowers on short stalks. It originated in the eastern Mediterranean and central Asia. Although not quite hardy, it is safe left in the ground over winter. Similar in shape, though not as large, Allium cristophii has short stems also and the starry flower heads make lovely dried flowers.
The most commonly grown kind is Allium aflatunense with dark purple-pink flowers in a tight round flower head about 10cms across. The stems vary but generally reach about one metre. This kind is easy to grow and reliable.
A form of this species called 'Purple Sensation' is outstanding. It has tall stems with deep purple flowers in a large ball. The giant onion, Allium giganteum, can throw up a flower stem close to two metres in height in good conditions, but the flower head is only about 10cm across.
A lovely form derived from this species, 'Globemaster' is a choice plant with large flower heads to 20cms in a deep purple starry, tightly held ball.
Alliums like well-drained soil in full sunshine. The soil need not be rich in nutrients but it should be fertile, otherwise alliums will not grow well and will stop flowering. In general, the stems do not need to be staked.
The broad blue-green leaves are quite pretty in their own right but begin to wither when the flower stems stretch up, and can be unsightly, best hidden behind a low plant, such as anthemis or dianthus.