Herbs in the Landscape

Giant Onion (Allium giganteum)

The large purple flower balls of this onion family plant bloom like lollipops in spring gardens. This ornamental perennial plant contains numerous small star-shaped flowers. A California bulb dealer counted 5286 florets from one umbel. This herb’s unobtrusive foliage of basal rosettes of grayish-green, strap-shaped leaves (to 18” long) allows them to blend in well with surrounding plants. It can grow to 3-5 feet tall. This plant is hardy in USDA Zones 5-8. Giant onion, also known as ornamental onion, originated in central and western Asia.

Giant onion will flower in May and June. The flower ball can be 5-6 inches wide. After flowering, the foliage dies back leaving a dormant underground bulb behind that can be dug up and replanted in a new area, if desired. It has a slightly garlic or onion-like aroma when the foliage and scapes are handled, yet it is not used for culinary purposes because it may cause gastrointestinal upset.

Giant onion needs abundant amounts of direct sunlight in order to thrive in the garden. Well-drained soil also is a must for survival of the bulb, especially during the winter. It prefers medium moisture, though a little more on the dry side. The bulbs are best planted about 9-12 inches apart in an area protected from wind. This herb is a low maintenance plant. It is virtually pest free and is shunned by both deer and rodents. The plants tolerate black walnut. To avoid fungal diseases, it is best to avoid watering from overhead. The genus name comes from the classical Latin name for garlic, and the specific epithet means giant.

The flower, both fresh and dried, makes a good cutting for flower arrangements. It is a dramatic border plant and looks best in plantings of 5-7 bulbs. It does well in gravel gardens. The flowers are attractive to pollinators, especially bees, birds, and butterflies.