Image Alt

Plant Search

Browse our inventory of prairie-strong plants.

Giant Onion

Allium giganteum

Add To My Plant List

print page
Giant Onion (Allium giganteum) at Eagle Lake Nurseries

Giant Onion flowers

Giant Onion flowers

(Photo courtesy of NetPS Plant Finder)

Giant Onion (Allium giganteum) at Eagle Lake Nurseries

Giant Onion in bloom

Giant Onion in bloom

(Photo courtesy of NetPS Plant Finder)

Plant Height:  12 inches

Flower Height:  4 feet

Spread:  12 inches

Sunlight:  full sun 

Hardiness Zone:  4a

Other Names:  Flowering Onion


One of the tallest ornamental onions, this selection looks beautiful as an accent in garden beds and in fresh or dried arrangements; large globes of small, purple, star shaped flowers stand above low mounded, fragrant green foliage; low maintenance

Ornamental Features

Giant Onion features bold balls of lightly-scented purple flowers at the ends of the stems from early to mid summer. The flowers are excellent for cutting. Its sword-like leaves remain green in colour throughout the season. The fruit is not ornamentally significant.

Landscape Attributes

Giant Onion is an open herbaceous perennial with tall flower stalks held atop a low mound of foliage. Its relatively coarse texture can be used to stand it apart from other garden plants with finer foliage.

This is a relatively low maintenance plant, and should only be pruned after flowering to avoid removing any of the current season's flowers. It is a good choice for attracting butterflies to your yard, but is not particularly attractive to deer who tend to leave it alone in favor of tastier treats. It has no significant negative characteristics.

Giant Onion is recommended for the following landscape applications;

  • Vertical Accent
  • General Garden Use

Planting & Growing

Giant Onion will grow to be about 12 inches tall at maturity extending to 4 feet tall with the flowers, with a spread of 12 inches. It grows at a medium rate, and under ideal conditions can be expected to live for approximately 8 years. As this plant tends to go dormant in summer, it is best interplanted with late-season bloomers to hide the dying foliage.

This plant should only be grown in full sunlight. It does best in average to evenly moist conditions, but will not tolerate standing water. It is not particular as to soil type or pH, and is able to handle environmental salt. It is highly tolerant of urban pollution and will even thrive in inner city environments. This species is not originally from North America. It can be propagated by multiplication of the underground bulbs.

Hardiness Zone Plant Height Minimum Sunlight
Articulation  Garden 
Flowers  Texture  Plant Form  Attracts Wildlife 
Ornamental Features