How to plant alliums
Also known as ornamental onions alliums grow in fertile well-drained soil. Most prefer full sun with the exception of allium ursinum (wild garlic) that thrives in shady woodland settings. Alliums do not thrive in waterlogged ground so if your soil is poor dig in a well balanced fertiliser such as liquid seaweed.
Plant your alliums between September and the end of November. The larger varieties like allium Beau Regard should be planted around 15cm deep and approximately 15 to 20cm apart (allow around 10 to 20 bulbs per square meter). The smaller flowering allium, Allium Moly for example, can be planted around 10cm deep and 8cm apart. For the large flowering allium for the smaller flowering allium (allow around 40 to 75 per square meter).
Most alliums will do well in deep pots. Use a John Innes No.3 soil mixed with compost or garden soil with a little added grit. Underplanting with other plants will disguise the dying leaves that can look a little messy. Small hostas are good companions and will provide extra colour throughout the summer months.
To keep your alliums flowering year on year lift divide overcrowded clumps after two to three years. Removing any tiny new bulbs and plant them in pots of in the garden until the bulbs are mature. It will take a few years for these to develop into flowering size bulbs but the wait is worth it.
Trouble shooting Avoid poor flowering results by always unpacking your bulbs on arrival and storing them in a cool place until you’re ready to plant them
Planting your bulbs too shallowly or in wet, soggy soil will also result in poor flowering so do follow the planting advice carefully.
Allium bulbs and plants can be poisonous to cats and dogs. Most animals wouldn’t dream of nibbling them but do take care to protect your pets.
Potential problems, pests and diseases:
All bulbs from the onion family are susceptible to similar problems such as onion fly, onion white rot and mildew. If you're planting your alliums in your allotment for cut flowers it is important not to plant where onions were previously planted or close to onions in other beds. Slugs and snails are also problems for allium so provide some protection.