Plantory
FeaturesPricingPlantsIdentify PlantBlogDocs
Plantory
FeaturesPlantsIdentify PlantGarden PlannerDocsAboutPrivacy PolicyTerms of Service

© 2026 Plantory. All rights reserved.

Plant data provided by Trefle.io and Perenual

HomePlant EncyclopediaGiant onion

Giant onion

Allium giganteum

Amaryllidaceae
Perennial
Ornamental
Attracts pollinators

About this plant

Allium giganteum, commonly known as Giant Onion, is a perennial ornamental plant belonging to the Amaryllidaceae family. It thrives in full sun with medium water requirements and is suitable for USDA zones 5–8. This plant typically grows to a height of 0.9–1.5 meters and produces striking purple flowers in late spring to early summer. It prefers loamy, chalky, or sandy soil and is known to attract pollinators.

Light

Full sun

Watering

Medium water

Soil

Loamy, Chalky, Sandy

Height

0.9–1.5 m

Spread

0.3–0.6 m

Zones

5–8

Flower colors

Calendar
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Bloom Period
J
F
M
A
M
J
J
A
S
O
N
D
Bloom Period
plantory.ai

Growing Tips

  • Planting: Plant bulbs in autumn or early spring.
  • Sunlight: Requires full sun for best flowering.
  • Watering: Water moderately, allowing the soil to dry slightly between waterings.
  • Soil: Prefers well-drained soil that is loamy, chalky, or sandy.
  • Support: Tall flower stalks may require staking in windy areas.
  • Aftercare: Remove spent flower stalks to prevent seed formation, though leaving some can provide winter interest.
Add to your garden plan

Unlock Full Plant Details

Sign up free to access the complete photo gallery, planting calendar, and add plants to your garden plan.

  • Monthly planting calendar
  • Add to your garden plan
Data source: Trefle.io
Back to Plant Encyclopedia