(AL-ee-um thun-BERG-ee-eye)

General Information:

The last plant to start flowering in my zone 5 garden is  Allium thunbergii ‘Ozawa’, the Japanese onion. As I write this it is October 26, 2014 and we have not had a real hard frost yet which is very unusual. Most common fall flowering plants like mums are finishing up but the Japanese onion is still going strong. It is not bothered by early frost or snow.

Allium thunbergii ‘Ozawa’; photo by Robert Pavlis

Most alliums flower in spring or summer. This one starts to make buds in early September but does not really open until early October, in most years. It then blooms for many weeks. I suspect the cold fall temperatures keep the buds fresh.

Some alliums spread quickly by seed making them weedy plants, but not this one. It forms a nice clump and rarely self-seeds—probably because the seed does not have time to ripen before winter. In early summer it produces nice grass-like foliage that looks nice all year, developing an orange colour after frost.

Allium thunbergii is also available as a white cultivar.

Allium thunbergii ‘Ozawa’; photo by Robert Pavlis

Life Cycle: bulb/perennial

Height: 30cm (1ft)

Bloom Time: fall

Natural Range: Japan and Korea

Habitat: low mountains, forest margins, slopes and pastures to 1300 m

Synonyms:  none

Cultivation:

Light: full sun to part shade

Soil: well drained

Water: not fussy, drought tolerant

USDA Hardiness Zone: 4– 9

Propagation: seed, division

Seedex availability (ORG&HPS annual Seed Exchange): frequently