Allium caeruleum (A. azureum)
- caeruleum (azureum)
- (Blue flowers)
- A. Flowering Characteristics
- A. caeruleum flowers in very late spring (May/June)
and lasts 2-3 weeks. Plants are 20 inches tall with small multi-flowered
- B. General Characteristics
- 1. Origin of species: North to Central Asia
- 2. Common names: Ornamental Onion
- 3. Geophyte organ: Tunicated bulb
- 4. Hardiness type: Hardy II - Injured at temperatures
below 14 degrees F (-10C) when planted.
- 5. Natural reproductive systems and growth and development
requirements: A. caeruleum reproduces by annual daughter bulb replacement
and seed and requires a warm (68 to 73F) - cool (28 to 32F) - warm (60F)
annual thermoperiodic cycle.
- 6. Primary uses: Perennial beds, rock gardens, meadows,
ground covers, and fresh cut flowers.
- C. Cultural Information
- 1. Bulb sizes: 4/5 and 5/up cm, in circumference.
- 2. Planting density: 2 inches apart, 15-25 bulbs per
- 3. Planting depth: 5 inches to base of the bulb.
- 4. Planting time: Fall
- 5. Climatic zone habit: 1990 USDA Climatic Zone 4 with
mulch, Zones 5 to 7 hardy without mulch.
- 6. Light requirements: Full sunlight only.
- 7. Moisture: Tolerates summer drought, but requires moisture
during growing season.
- 8. Animal susceptibility: Normally not susceptible.
- D. Companion Plants:
- Alyssum, Baptisia, Dryopteris erythrosora, Coreopsis,
Hemerocallis, Iris (rhizomatous), Kniphofia, Peonies, Stokesia,
Verbascum, Acer palmatum, Buddleia, Cotoneaster, Deutzia gracilis, Kalmia,
Rhododendron spp., Spiraea spp., Viburnum, 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.