How to Grow Alliums

Alliums are stylish plants with tall stems and large blooms which look fantastic in borders with large round flower heads. The good news is that Alliums are easy to grow and are a perennial which generally returns reliably every year.   

Alliums flower in shades of purple, white and occasionally blue and yellow. Alliums are bulbs and almost trouble free. The only maintenance required for Alliums is that the taller species need staking to prevent the flower stem from being damaged, unless planted in a sheltered spot away from wind. Although Alliums are in the section of spring flowering, it is true to say the majority are spring and early summer flower. There are some varieties which flower during late summer. 

Alliums are loved by bees and insects and on a warm day the large flower heads will be buzzing. They will also attract butterflies and are a great source of nectar.

Alliums are best planted in the autumn when you can buy bulbs at a reasonable price. Ready grown container plants are available from early spring onward but naturally these are more expensive. It is significantly cheaper to buy and plant Alliums as bulbs.  Alliums prefer a sunny position in soil which is not waterlogged and they are fully hardy tolerating our winters well. However, if your garden has heavy soil or ground that tends to be wet, it will help to work horticultural grit into the planting area to increase drainage. This should prevent the bulb rotting over winter which can be a problem in wetter areas.

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

Smaller varieties should be planted 15-20 cms apart, large varieties (such as a.cristophii)  25-30cms and the very large ( such as Globemaster' and schubertii)35cms+ 

Like all bulbs, do not cut or clear away the old foliage after flowering as this is needed to photosynthesise and feed the bulb for next year.

Alliums are drought tolerant, generally do not need feeding or dead heading, quite the reverse as many of the flower heads look very decorative as they fade. 

Individual plants make an impressive single statement in the border, (top left) and the Allium illustrated is 'Globemaster'.

Alliums are 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 as the seed heads form, illustrated below right.

 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 late flowering Allium such as A. sphaerocephalon so that it is at its best when the grasses are looking good and the Achillea in flower.

Alliums 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. 

 Allium are illustrated here:-

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.

Centre image above is Allium sphaerocephalon, a late summer flowering variety. It looks good planted with grasses which are at their best in late summer and early autumn, and also with late flowering perennials such as Rudbeckia and Helenium.

In the third image above is the 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.

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.