Alliums, also known as ornamentals onions, come in shades of purple, white or yellow. The majority of ornamental onions flowers in early summer. They need full sun and well-drained soil. So avoid soils that are too wet.
Allium ‘Purple Sensation’
A lovely allium with dark violet flowers, forming together a globe with a diameter of 10cm. It flowers in late May and early June. Plant in a group to create a striking show.
The spherical heads of Allium ‘Globemaster’ are densely packed with tiny, violet star-shaped flowers. The flower heads, 20cm in diameter, appear in early summer on stems to 80-100cm in height.
The flowers of ‘Globemaster’ are sterile. So they don’t produce seed.
Allium sphaerocephalon Allium ‘Purple Sensation’
Allium sphaerocephalon produces small, reddish-brown drumstick-shaped flower heads on long wiry stems. This allium will reach a height of 60cm. It will self-seed.
Pruning alliums (ornamental onions). Cut off the spent flower heads at the base of the plant after flowering. Alternatively, leave the dried flowers heads on. They will add interest to winter borders.
Planting allium bulbs
How and when to plant allium bulbs. They are best planted in the autumn (October-November). Leaves of allium start to turn yellow as the plant flowers. Plant the bulbs between low-growing perennials to conceal the tatty leaves.
Planting depth. Allium bulbs should be planted at least three times the depth of the height of the bulb. The top of the allium is pointed. Plant large bulbs 20-25cm apart. Plant smaller varieties 10-15cm apart.
The bulbs are hardy. After flowering, they can be left in the ground to over-winter.
Feed the alliums bulbs with a high potash liquid feed after flowering.
During late summer you can divide allium bulbs after the flowers and leaves have died down. Dig up the bulbs and remove the offsets. You can then replant into the soil.