When to plant allium bulbs

What do allium bulbs look like?

There are few spring bulbs more delightful than an allium. Allium bulbs bloom into magnificent, pom-pom-like flowers that sit precariously on top of tall, single stems for weeks. Usually purple, (but sometimes white, pink or blue) each head is covered in hundreds of tiny blooms, adding colour, character and height to beds and borders. They’re also drought tolerant and perfect for container gardening, making them a winner whichever way you look.

Once the globe flowers have passed, the sparkler-like seed heads continue looking spectacular. Cut them to dry indoors or leave them to add extra decoration to beds and containers throughout the summer.

When to plant allium bulbs

You’ll find lots of allium bulbs for sale in the UK from late summer into autumn. Get these little clusters of potential planted between September and November to enjoy powder-puff flowers from May to July.

Some newer varieties, like allium ‘Millenium’ bulbs can be planted in early spring and will flower right through to August.

How to plant alliums

Alliums are ornamental members of the onion family (with a much friendlier scent). They love nothing more than full sun and well-drained soil but will tolerate most conditions so long as the ground isn’t waterlogged.

If you’re growing a very tall variety, bed them in a sheltered spot to stop them from flailing and breaking in the wind.

How to plant alliums in pots

Alliums don’t like much water so choose a pot with drainage holes, put crocks (broken pot shards) in the bottom and raise them on pot feet or bricks to make sure the compost can drain freely.

1. Grab a deep pot and half fill it with peat-free compost, mixed with a couple of handfuls of grit.

2. Place the allium bulbs on the surface, around 10 cm apart, or a little more if you’re planting large alliums.

3. Top the pot up with more compost, firm the surface and water the bulbs in.

How to plant alliums in the ground

Planting alliums in the ground couldn’t be easier. If you have a bulb planter, it’s easier still.

1. For a natural look, scatter your allium bulbs over the ground and use a bulb planter or a trowel to make a hole where each one lands. Alliums should be planted at 2-3 times the depth of the bulb. Smaller plants should be around 10cm apart. Larger varieties need at least 20cm between bulbs.

2. If you’re growing on clay, add a sprinkle of grit to the bottom of each hole. Place one bulb in each, with the pointy end facing up.

3. Cover each bulb up with soil and water them all in.

How to care for alliums

Alliums are drought tolerant so, after planting, you shouldn’t need to water bulbs in the ground unless there’s a particularly dry spell. As with all container plants, you’ll need to water allium bulbs in pots regularly but don’t go overboard as waterlogged compost = rotting bulbs.

There’s no need to deadhead the plants after flowering. The dried seed heads are the epitome of garden glamour and can be left to twinkle like stars in your borders, providing food and shelter for bugs and birds until the end of the season.

Unlike some other spring flowers, allium bulbs can be left in the ground over winter and don’t need lifting.

Move pots of alliums into a sheltered spot to avoid frost damage, or dig the bulbs out, clean them up and dry them before storing them in a cool, dark place and planting them up as part of a new display in autumn.

Do allium bulbs multiply?

Over time, allium bulbs will multiply and your beds might start to look a little…crowded. If your alliums are jostling for space, use a fork to dig the bulbs up after the flowers have died back. Pull a few out to divide them and plant the smaller bulbs in other areas of the garden. Or gift them to a friend and spread the planty love.

What to plant with alliums

Alliums are proper stunners as part of a spring flower display. Being tall, they’re ideal for adding height to borders and container gardens. Underplant them with late flowering tulips, clash them with luminous orange geums, mix them up with cottage garden roses and lavender, or create a prairie-style bed by pairing them with feathery grasses and swaying salvias.