Ornamental Onion (Allium Globemaster) Growing & Care Guide for Gardeners.

Article by Dean Ravenscroft, Ph.D.

Gardener's HQ Guide to Growing Ornamental Onion

Allium giganteum 'Globemaster' often called Allium Globemaster, or Ornamental onion, has wonderfully 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 colorful flowers in spring.

Globemaster Alliums photograph by Kim Carpenter.

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

Ornamental Onion 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.

Common Questions

How many members does the Allium genus have?

The Allium genus is large, with around 800 species. Commonly known members include onions, garlic, leeks, chives, and ornamental varieties.

Is Allium Globemaster a good plant to use in the garden and/or for landscaping?

Allium Globemaster is a great choice for gardens and landscaping. Its large, vibrant purple blooms help to add height and effect to any setting.

Is it a fragrant plant?

Allium Globemaster has a mild onion-like fragrance. This smell is more prominent when its leaves or bulbs are crushed.

What is the ideal Garden location to grow Allium Globemaster?

A good garden location for Allium Globemaster is in full sun with well-draining soil. It looks great in borders, beds, or growing among other perennials.

How do I remove Ornamental Onions from my garden?

To remove Ornamental Onion, simply dig up the bulbs when the plant is dormant. Removing all bulb offsets should prevent regrowth. If you dispose the bulbs away from your garden it should help protect from them becoming re-establised.

Summary

Allium giganteum 'Globemaster' is a perennial bulbous plant that is grown for its large spherical purple blooms. Ideally grown in full sun, they will thrive in a well-draining soil. They are suitable for borders, beds, or among perennials. Plant the bulbs in the autumn, at a depth of about 6-8 inches (15 to 20 cm). It is a great plant to use to add dramatic height and color to a garden in late spring to early summer.

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.