How to Grow Allium Globemaster Plants in your Garden

Gardener's HQ Guide to Growing Ornamental Onion

Allium Globemaster, or Ornamental onion, has showy, deep lavender, ball-shaped blooms.

A member of the amaryllis family (Amaryllidaceae), this low-maintenance perennial grows from bulbs and will provide years of pleasure.

Hardy in USDA Zones 5 to 8, Allium Globemaster reaches a height of 1.5-2.5 feet (45 to 7 cm) and produces giant balls of colourful flowers in spring.

It is a great wildlife garden plant as ornamental blooms rise up on stout stems to attract butterflies once the greyish green leaves begin to wither in mid-spring.

Allium globemaster
Globemaster Alliums photograph by Kim Carpenter.

Globemaster's flower heads may reach as much as 6-10 inches (15 to 20 cm) in diameter, making it a striking accent plant. These impressive blooms are long lasting and created from individual florets in the shape of stars.

Following blooming, flower heads dry and continue to be attractive well into the summer months.

Placing them behind plants with heavy foliage such as Peonies or Iris will produce a lovely scene.

The flower heads are also good for drying. Many gardeners immensely enjoy Allium Globemaster as a naturalized flower.

Gardener's HQ Guide to Growing Ornamental onion

This lovely plant likes full sun but partial shade in the afternoon is a bonus on hot summer days.

It prefers a dry to medium moisture well-drained soil, and will tolerate a wide range of soil types and pH acidities. If your soil is clay, sand may be added to improve drainage.

Ornamental Onion Globemaster does not produce seeds. It is best to plant new bulbs in autumn /fall at 4-6 inches (10 to 15 cm) deep or at three times the diameter of the bulb.

Space Allium Globemaster at about 12 inches (30 cm) apart.

If you require further plants then dig bulbs of established plants to divide and replant in late summer or early fall, be sure to wait until the foliage has died down.

Allium Globemaster Growing and Care Guide

  • Scientific Name: Allium Globemaster
  • Common Name: Ornamental Onion
  • Growing Zone: USA: 5 to 10
  • Life Cycle / Plant Type: Perennial

Plant Details

  • Plant Height (Inches): 36 to 60
  • Plant Spread (Inches): 2 to 12
  • Time of Bloom: Early summer to Mid summer
  • Flower Details: Purple
  • Leaf Foliage: Green
  • Fruit:
  • Growth Form: Upright / erect

Ideal Growing Conditions

  • Best Light Conditions: Full sunlight
  • Rate of Growth: Quick
  • Suitable Soil Types: Loamy, Neutral, Sandy, Well drained
  • Soil Moisture: Moist

Caring Conditions

  • Care:
  • Level of Maintenance: Low
  • Propagation: Seed, sowing in containers in a cold frame when just ripe or in the spring. Alternatively, remove offsets in autumn
  • How to Prune: Not usually required
  • Pests: Usually pest free
  • Diseases: Mainly trouble free, Onion white rot and downy mildew

Further Information

  • Can Attract: Butterflies
  • Tolerant of: Deer, Drought, Black Walnut
  • Best Garden Use: Container, Foundation, En masse , Rock garden, Specimen
  • Family: Amaryllidaceae.
  • Closely Related Species: Agapanthus, Amarylis, Leucojum, Lycoris, Galanthus, Narcissus, Nerine,Sprekelia, and Zephyranthes.

  • Miscellaneous: Attractive foliage, Fragrant foliage, Attracts butterflies, Suitable for cut flowers, Suitable for dried flowers
  • Genus Detail: Allium
  • Further Reading and References: Here and Here

I hope that you enjoyed this guide on how to grow Allium Globemaster. You may also enjoy the following growing guides: How to grow Allium aflatunense and Allium moly.