Alliums are long-lived bulbous perennials, flowering for several weeks from spring to early summer. Loved by bees, they bear beautiful pompom flowers in shades of purple pink and white, and look fantastic when planted in large groups. Alliums make excellent cut flowers, both in fresh and dried flower arrangements.
How to grow alliums
Grow alliums in moist but well-drained soil in full sun. It’s a good idea to grow them among low-growing herbaceous plants, which hide their unsightly strappy foliage after flowering. Let allium foliage die down naturally after bloomig and consider leaving the flowerheads in place as they look attractive in their own right, particularly in winter. Mulch annually with well-rotted compost or manure.
More on growing alliums:
Where to plant alliums
Alliums do best in a sunny spot in a very well-drained soil. They’re not fussy about soil type. Plant taller varieties towards the back of a border and shorter-growing types in the front. Alliums are well suited to growing in pots but their strappy foliage can look unsightly after flowering.
For a dramatic display, grow alliums in large drifts through the border or naturalise them in your lawn.
How to plant alliums
Plant allium bulbs in autumn, at least four times the depth of the size of bulb. It’s better to plant them too deeply than too shallow.
If the soil is moist there’s no need to water them in. In spring, when growth starts to appear, apply a balanced fertiliser to poor soils.
Watch our No Fuss video guide with Rosie Yeomans, to learn how to layer allium bulbs with others in a pot:
How to care for alliums
Taller types may require support in exposed positions. Once the flowers have faded leave them on the plant until they fall apart as they offer fantastic winter interest. Some gardeners pick the seedheads and dry them in order to use them as a decoration in the house.
Alliums can be left in the garden year after year. Try to remember where you’ve planted bulbs so you don’t damage them when planting new plants.
How to propagate alliums
After a few years allium bulbs will multiply. In some cases you’ll notice the white bulbs being pushed out of the soil. In late autumn or very early spring carefully lift the bulbs and gently peel off the offsets to replant straight into the soil.
To grow allium from seed leave the flowerheads on the plant and collect the ripe seed and sow it straight away. bear in mind that growing alliums from seed is a long process, as it will be years before you achieve a flowering plant.
Growing alliums: problem solving
Alliums produce foliage before the flowers appear. This often means they’re better suited to the middle of a border where the faded foliage will go unnoticed while the flowers put on a show. To avoid seeing the faded foliage, plant alliums in amongst ornamental grasses and perennials.
Allium white rot is a fungal disease, which inhibits the growth of onions and other alliums. To prevent recurrent infections, clear and burn the affected plant material and avoid planting alliums in the same position for at least five years.
Alliums can out-grow their space. Find out how to reduce the number of alliums growing in a border, in this video clip from Gardeners’ World:
Allium varieties to grow
- Allium hollandicum ‘Purple Sensation’ – intense purple, globe-shaped flowers held on 75cm stems. The May flowers measure 10cm across
- Allium ‘Mount Everest’ – white, globe-shaped flowers held on 90cm stems. The May/June flowers are 10cm across
- Allium sphaerocephalon – smaller flower heads in June or July that start green and turn a deep pink. Reaches a height of 60cm but does tend to romantically fall about
- Allium cristophii – offers impressive flowers that are 20cm across held on stems of 20cm in June. The purple head of flowers is quite open unlike the tightly packed ‘Purple Sensation’. Dramatic silvery foliage
- Allium moly – small but very bright yellow flowers that can thrive on a woodland edge. Flowering in May or June on 30cm stems