How to grow Alliums

 Alliums are an easy to grow bulb which is perennial and usually returns reliably every year.   

Alliums come in a wide range of heights, from low growing chives to the tall varieties such as A. allium giganteum which can reach 1.5m. Alliums are mainly late spring/early summer flowering, although there is a late summer flowering variety Allium sphaerocephalon .

Alliums flower in shades of purple, white and occasionally blue and yellow. Alliums are bulbs and almost trouble free. The only maintenance required is that the taller species need staking to prevent the flower stem from being damaged, unless planted in a sheltered spot away from wind. Bees and insects love alliums, and on a warm day the large flower heads will be buzzing and they will also attract butterflies.

Allium Bulbs are best planted in the autumn when you can buy bulbs much cheaper than in the Spring when they are sold as pot grown plants. Planting time is September, but if you are late, you can carry on planting Allium bulbs until about the 3rd week of October. Ready grown container plants are available from early spring onward, but naturally these are more expensive. 

Alliums prefer a sunny position in soil which is well drained and they are drought tolerant. Alliums are fully hardy tolerating our winters well. However, if your garden has heavy soil or ground that is 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,  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 decorative as they fade. 

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

Alliums are members of the onion family and the small Allium schoenoprasum, Chives, are good to eat and make a lovely edging plant in the front of a border and are wildlife friendly. 

 Allium illustrated above 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.

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 knows how to put on an impressive display and this is Alliums on mass with grasses growing at RHS Harlow Carr, something to aspire to. 

last updated 10.10.2022