Scientific Name
Allium cowanii
Common Name
Ornamental Onion
ALLIUM
cowanii (White flowers)
A. Flowering Characteristics
A. cowanii flowers in the late spring (May) and lasts 2-3 weeks. Plants are about 16 inches tall with large multi-flowered umbels.
B. General Characteristics
1. Origin of species: Southern Europe and Northern Africa.
2. Common names: Ornamental Onion
3. Geophyte organ: Tunicated bulb
4. Hardiness type: Tender III - Injured at temperatures below 35 degrees F (2C) when planted.
5. Natural reproductive systems and growth and development requirements: A. cowanii reproduces by annual daughter bulb replacement and seed and requires a warm (68 to 73F) - cool (35 to 50F) - warm (60F) annual thermoperiodic cycle.
6. Primary uses: Perennial beds, rock gardens, ground covers and cut flowers.
C. Cultural Information
1. Bulb sizes: 4/5 and 5/up cm, in circumference.
2. Planting density: 4 inches apart, 9 bulbs per sq. ft.
3. Planting depth: 5 inches to base of the bulb.
4. Planting time: Fall
5. Climatic zone habit: 1990 USDA Climatic Zone 8 with mulch, Zones 9 to 10 without mulch.
6. Light requirements: Full sunlight only.
7. Moisture: Tolerates summer drought, but keep moist during growing season.
8. Animal susceptibility: Normally not susceptible.
D. Companion Plants:
Annuals, Alyssum, Arabis,Coreopsis,Hemerocallis, Hosta cvs., Iris (rhizomatous), Kniphofia, Rudbeckia, Sedum, Stokesia, Verbascum, Verbena, Zephyranthes, Buddleia, Cleyera, Hypericum, Oleander, Illicium, Pittosporum, Rhododendrum spp., Spiraea spp., Weigela.

Holland Technical Service Bulletin Number 31 was prepared for the WWW system by A.A. De Hertogh, L.B. Gallitano, M.E. Traer, and A.B. Russell, Department of Horticultural Science, NC State University. The information was obtained not only from original research conducted by the authors but also from databases released by other sources. This Bulletin was published by the International Flower Bulb Center (IBC), Hillegom, the Netherlands on behalf of the Dutch Flower Bulb Industry. Because of the various climates in North America and year-to-year variability of the weather, the IBC cannot and does not accept responsibility for divergent results that may arise using information obtained from this document or site. Photographs copyright @1997 by A.B. Russell and A.A. De Hertogh. Computer programming by Miguel Buendia, graphics by Brad Capel.