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Purple allium
Purple allium

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Allium

Ornamental Allium
Liliaceae
Bulbs and bulblike plants, Perennials

About 500 species, all from the Northern Hemisphere, many from the mountains of the West. Relatives of the edible onion, they are peerless as cut flowers (fresh or dried) and useful in borders; smaller kinds are effective in rock gardens. Bear small flowers in roundish, compact or loose clusters at ends of leafless stems that range in height from 6 in. to 5 ft. or taller. Many are delightfully fragrant; those with onion odor must be bruised or cut to give it off. Bloom in spring or summer, with flowers in white and shades of pink, rose, violet, red, blue, and yellow.

All prefer well-drained soil (preferably on the sandy side), enriched before planting with organic matter. In fall or spring, plant bulbs as deep as their heigh or width, whichever is greater. Space smaller species 4–6 in. apart, larger ones 8–12 in. apart. Cut back on watering or let soil go dry when foliage begins to yellow after flowering. Foliage dies to the ground, even in mild-winter areas. Lift and divide only after clumps become crowded.

Allium aflatunense

Clusters of lilac flowers on stems 2 1/2–5 ft. tall. Resembles A. giganteum but with smaller flower clusters; blooms in spring.

Allium caeruleum

Cornflower blue flowers in dense clusters to 2 in. across on 1–2-ft.-tall stems. Late spring bloom.

Allium cristophii (photo courtesy of Denver Botanic Gardens)
Allium cristophii (photo courtesy of Denver Botanic Gardens)

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Allium cristophii

Distinctive plant, with very large clusters (6–12 in. across) of lavender to deep lilac, starlike flowers with a metallic sheen, appearing in late spring. Stems are 12–15 in. tall. Leaves to 1 1/2 ft. long, white and hairy beneath. A dried flower cluster looks like an elegant ornament.

Allium giganteum (photo courtesy of Denver Botanic Gardens)
Allium giganteum (photo courtesy of Denver Botanic Gardens)

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Allium giganteum

Summer bloomer bearing spectacular softball-size clusters of bright lilac ­flowers on stems to 5 ft. or taller. Leaves are 1 1/2 ft. long and 2 in. wide.

Allium schoenoprasum (photo courtesy of Denver Botanic Gardens
Allium schoenoprasum (photo courtesy of Denver Botanic Gardens

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Allium schoenoprasum

Plant forms clumps to 2 ft. high (usually shorter) of dark green leaves that look grasslike but are round and hollow. Clusters of rose-purple flowers (like clover blossoms) appear atop thin stems in spring. Use as edging in flower border or herb garden. Chop or snip leaves; use as garnish for a delicate onionlike flavor.

Allium sphaerocephalon

Tight, dense, spherical red-purple flower clusters top 2-ft. stems in summer. Spreads freely.

Allium tuberosum (photo courtesy of Denver Botanic Gardens)
Allium tuberosum (photo courtesy of Denver Botanic Gardens)

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Allium tuberosum

From Southeast Asia. Clumps of gray-green, flat leaves 1/4 in. wide and 1 ft. long or less. Abundance of 1–1 1/2-ft.-tall stalks bear clusters of flowers in summer. Flowers have the scent of violets and are excellent for fresh or dry arrangements. Leaves have a mild garlic flavor and are useful in salads and cooked dishes.

Allium unifolium (photo courtesy of Denver Botanic Gardens)
Allium unifolium (photo courtesy of Denver Botanic Gardens)

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Allium unifolium

California native. Satiny, lavender-pink flowers on 1–2-ft. stems in late spring. Spreads freely but is not a pest.

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