How to Grow Alliums

Alliums are stylish plants with tall stems and large blooms. They look fantastic in the borders with the large pom pom heads of flowers. The good news is that Alliums are easy to grow and return reliably every year.   

Alliums are tall and their large flower heads are in shades of purple, white and occasionally blue and yellow. Alliums are bulbs, easy to grow and almost trouble free. The only maintenance required for Alliums is that the taller species need staking unless planted in a sheltered spot away from wind. The different varieties of Allium bloom at slightly different times both spring, summer and autumn flowering.

Alliums are planted as bulbs in the autumn, and are also sold as ready grown container plants from early spring onward. It is significantly cheaper to buy and plant Alliums as bulbs.  Alliums prefer a sunny position in soil which is not waterlogged and are fully hardy. If you garden on heavy soil or ground that tends to be wet, it may help to work horticultural grit into the planting area to increase drainage.

When planting Alliums, in common with many bulbs,  sink and plant to 3 times the depth of the bulb. 

A real plus point about Alliums is that they look good with many of our popular garden plants. Planted together on mass they are effective as in the large image  which was taken at RHS Harlow Carr.  Individual plants make an impressive single statement in the border, (top left) and the Allium illustrated is 'Globemaster'.

Alliums are just made to mix with grasses and look good with Achillea (2nd image centre). Alliums are predominately purple flowering although there is a blue form, careruleum, and a very attractive yellow variety, Allium moly (golden garlic) which has umbel type flowers in the summer. Alliums have an additional bonus that the flower heads look good as they fade and the seed heads form as illustrated below right.

The downside of growing Alliums, if there is one, is that the leaves at the base of the plant can look a bit tired, or ragged quite early on in the growing season.   This means it's a good idea to conceal the base growth with low growing plants, such as the Alchemilla mollis and Geraniums which look well with Allium. If you are combining with other plants check the variety to ensure the flowering times coincide. To plant the combination of grasses and Alliums illustrated centre above and below left it is essential to plant a later flowering Allium such as sphaerocephalon.

Alliums are loved by bees and insects and given a warm day the large flower heads will be buzzing. They are members of the onion family and the small Allium schoenoprasum, Chives, are good to eat and make a lovely edging plant front of the border and are wildlife friendly. 

   If Allium is not the plant for you check out other spring flowering plantsscented plants and climbing plants for more ideas.    

Allium and grasses at RHS Harlow Carr

Of course, the RHS always know how to put on a great display and this is Alliums on mass with grasses growing at RHS Harlow Carr, something to aspire to. 

The Best Alliums to Grow

Many varieties of Allium are illustrated here.

Very popular Alliums with the RHS garden merit award are:

A. cristophii (image top right) is short at 60cms with spiky flower head which will self seed in the right conditions;

A.hollandicum (image below) 'Purple Sensation' tall 80cms dark purple;

A. Globemaster 100cmc with large deep purple flower heads.

Images Above: image first left Globemaster which is summer flowering and grows up to 100cm.

Centre is Allium sphaerocephalon which flowers in late summer and  looks very good with grasses which are at their best in late summer and early autumn.

In the third image, very attractive A. christophii which flowers in the late spring and early summer, with spiky flower heads which look very good as they fade and dry.

Green wheelbarrow means Alliums are easy to grow and low maintenance

Best Allium Planting Combinations

Allium hollandicum ‘purple sensation’ with Euphorbia palustris

For contrasting colours: Allium 'Purple Sensation' with Euphorbia palustris which make a great contrasting combination. This is a late spring early summer combination.

Allium stipitatum ‘white giant”

Simplicty: Allium stipitatum White Giant which looks really good planted as a group with the wall as a backdrop.

Alliums planted en masse

For a Soft Blues and Mauve combination: Allium planted grouped together look impressive this and the large image above was taken at RHS Harlow Carr. In another area of the garden Alliums were planted up with a blue variety of Camassia. This is a good blue/purple combination bearing in mind Camassia may not be fully hardy everywhere in the UK.

Deschampia grasses with Alliums

Late summer combination: Alliums and grasses are natural companions; this combination is Deschampsia grass with Allium sphaerocephalon, a soft billowing grass making a rich late summer/autumn display combined with the deep purple Allium and just a little blue mixed in from the Nigella damascena common name "love-in-a-mist'.

Allium chives, in wildflower setting with campion and for get me nots

Wildlife friendly combination: Chives with forget me nots and Campion. It is easy to overlook A. schoenoprasum, Chives, as it is small but ideal for edging and at the front of a border it is very bee friendly. Chives flower for weeks and can be cut back to produce fresh growth and a second set of flowers.  In this combination chives have been planted with Forget me nots and Campion, a lovely planting combination.

Fading flower heads of Alliums

Staying Power: Allium fading flower head last for along time looking impressive. This imagee shows the delicate beauty of the fading flower heads. Alliums belong o one of those unique group of plants whose flowers look really good as they fade, (think also Hydrangea, and Achillea.)

Allium schubertii, with candelabra primular and blue geranium 310

Great spring combination: The aritectual spikey Allium schubertii, with candelabra primular and blue hardy geranium makes an easy to grow colourful combination

Allium against a backdrop of clematis montana

Contrasting combination of Allium Globemaster against a back drop of the spring flowering Clematis montana makes an interesting combination.

Key Points to Growing Allium

Fully Hardy 

Enjoys sun and well- drained soil

Plant the Allium bulb in autumn 3x its depth 

 Support tall varieties. 

Easy to grow, reliable performer flowers every year.