Plant Guide: Allium

Allium includes a wide range of plants, covering not only edible species such as onions, garlic and chives, but also many ornamental varieties. A typical feature is the spherical flower head, usually purple in colour, although yellow and white forms also occur. Plant height varies greatly: smaller species such as Allium moly reach around 20 cm, while Allium giganteum produces striking flower stems of 100 cm or more. After flowering, the dried flower heads often remain decorative and can be used in dried arrangements.

How to plant

Allium bulbs are planted in autumn, preferably between September and November, before the soil freezes. The bulbs are planted in well-drained soil that has been improved with compost. Planting depth depends on bulb size; as a general rule, bulbs are planted at a depth of approximately three times their own height, which usually equals about 10 to 15 cm deep. Spacing between bulbs is typically 10 to 20 cm, depending on the species. Choose a sunny position, although light shade is also tolerated. In borders, Allium is often planted among other plants to help disguise the dying foliage.

Flowering period

Flowering takes place in late spring and early summer. During this period, the spherical flower heads rise above the foliage. Once flower buds appear, fertiliser can be applied generously. Water during dry periods, but ensure the soil does not become waterlogged. Flower stems may be cut when approximately half of the flowers have opened.

After flowering

After flowering, the leaves gradually die back, sometimes while the plant is still in bloom. Spent flower heads can be removed, and watering should be stopped once flowering has finished. If bulbs become overcrowded, they can be lifted and divided in autumn, then replanted immediately at the correct depth.