Alliums are ornamental onions, bold and architectural, with large rounded heads of usually purple flowers and attractive seedheads. Weave them through sunny borders or combine them with feathery grasses for best effect. They are available in shades of blue, purple, mauve, pink, yellow and white and with a range of flower head sizes from just a few centimetres to 18-20cm (7-8in) in diameter. Most flower in the months of May and June.

When to plant allium bulbs

Achieve the perfect pom-pom display by planting allium bulbs ahead of spring. From planting tips to nurturing guidance, here's all you need to know for cultivating these vibrant spheres.

What do Allium Bulbs Look Like?

Allium bulbs bloom into stunning pom-pom-like flowers atop tall, slender stems, showcasing a plethora of tiny blooms in shades of purple, white, pink, or blue. Not only do they add colour and height to gardens, but they're also drought-tolerant and ideal for container gardening, offering versatility and charm.

Once the globe flowers fade, their sparkler-like seed heads continue to enchant, whether dried indoors or left as natural embellishments in beds and containers throughout the summer.

Allium bulbs are widely available in garden centres and online in the autumn. Buying plants in flower in spring or early summer gives you the chance to choose the best flower type for your garden. Alliums are drought tolerant and watering of plants grown in the ground is not usually necessary. Plants dislike summer irrigation because this may cause the bulbs to rot. Alliums grown in containers will need regular watering, but make sure the compost does not become waterlogged.

When to Plant Allium Bulbs

In the UK, allium bulbs are typically available for purchase from late summer to autumn. Plant these clusters of potential between September and November for a blooming spectacle from May to July. Certain newer varieties, like allium 'Millenium,' can be planted in early spring, offering blossoms that persist through to August.

How to Plant Alliums

Alliums, ornamental members of the onion family, thrive in full sun and well-drained soil, though they're adaptable to various conditions if the soil isn't waterlogged. For taller varieties, opt for sheltered spots to prevent wind damage.

Planting Alliums in Pots

Follow these steps for planting alliums in containers:

  • Select a deep pot with drainage holes and place broken pot shards at the bottom for adequate drainage.
  • Fill the pot halfway with peat-free compost mixed with a handful of grit.
  • Space the allium bulbs about 10 cm apart on the surface.
  • Cover the bulbs with more compost, firm the surface, and water thoroughly.

Planting Alliums in the Ground

For a natural look, follow these steps for planting alliums in the ground:

  • Scatter the allium bulbs over the ground and use a bulb planter or trowel to make holes at a depth of 2-3 times the bulb's size.
  • Space smaller bulbs around 10 cm apart and larger ones at least 20 cm apart.
  • If planting in clay soil, add a sprinkle of grit to each hole.
  • Place one bulb in each hole with the pointy end facing up.
  • Cover the bulbs with soil and water them in thoroughly.