PLANTING
Plant bulbs at three times their own depth in the soil in autumn and space them about 20cm apart (or 10cm apart in the case of smaller bulbs, such as ‘Eros’).
Some alliums have rhizomes (underground stems) instead of bulbs. These look more like spring onions than dry bulbs on arrival. Plant these in autumn just below the soil surface and 10cm apart. Alliums aren’t too fussy, but a sheltered spot with well-drained soil in full sun is ideal.
Alliums can also be grown in pots as long as you plant them at the necessary depth.

Caption: Plant the bulbs in autumn

CARING FOR YOUR PLANTS
The leaves of most alliums are unattractive at best. The saving grace is that they generally die away by the time the flowers are in full bloom and if you plant your alliums in a full border, you’re unlikely to  notice the brown foliage. However, if you find the mess is detracting from the flowers, either remove the leaves once they’ve turned yellow or plant beneath the alliums to hide the leaves. We recommend hardy geraniums, such as Best Buys ‘Mount Olympus White’ or ‘Orkney Cherry’, Japanese anemones, such as Best Buy ‘Wild Swan’, or pennisetum. We don’t recommend removing the foliage while it’s still green as the leaves help the bulb produce flower heads for the next summer.

Caption: Grow alliums through other plants to hide the foliage

Remove any stems that become detached at their bases in late summer. You can also cut them off in June so that you can dry them indoors to use them as decorations.

Caption: Allium cristophii 

PROBLEMS
Alliums are generally trouble-free in borders, but watch out for the orange spots of rust and cut back diseased foliage. Pests to keep an eye out for include slugs, snails and allium leaf miner.
Alliums are hardy in the UK and can be left in the ground all year.