Onion Allium

This genus contains approximately 700 species in the amaryllis family (Amaryllidaceae)and is commonly called onions or ornamental onions. It includes the ones we eat for food as garlic, shallots, chives and onions and the ones grown ornamentally in our gardens. Many are native to the northern hemisphere where they can be found growing in dry, mountainous regions, forests and disturbed areas. Others are native to Europe and Asia.

Size varies per species but average height is 1-3 feet tall. Most species will do well in full sun to light shade in fertile loose well-drained soil. To propagate species that form bulbs, division is easies from bulb offsets. These should be divided and planted in spring for the best results. Sowing from seed is also an option but some seeds may take years to germinate. After flowering, the foliage may look unwell so the leaves should be cut back to revive the plant’s interest. To protect plants over winter months, dig and store any non-hardy species. 

Flowers are produced on erect or pendant scapes and have 6 petal-like sepals in two rows. Leaves vary per species. Some have basal leaves that wither when the plant flowers and others have persistent leaves. Most plants have an onion or garlic odor to the leaves and flowers.

Many ornamental onions are edible and are used in the home vegetable garden. Ornamental ones are great for perennial borders, rock gardens, pollinator gardens or as mass planting. 

Pests, Insects, and Other Plant Problems: Overly damp conditions leave ornamental onions prone to fungal issues, including bulb rot, white rot, rust, and mildew.

VIDEO created by Andy Pulte for “Landscape Plant Identification, Taxonomy and Morphology” a plant identification course offered by the Department of Plant Sciences, University of Tennessee.