Giant Ornamental Onion Allium giganteum
Other Common Name(s):
Previously known as:
- Allium procerum
- Phonetic Spelling
- AL-ee-um jy-GAN-tee-um
- This plant has low severity poison characteristics.
- See below
- Description
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Ornamental Onion is a bulbous herbaceous perennial in the onion family (Amaryllidaceae) native to the Himalaya region and found growing in forests, naturalized areas, and in disturbed areas where it has the potential to be weedy.
The plants can grow up to 6 feet tall and 2 feet wide and prefer full sun in well-drained amended garden soil. Plant in fall at a depth of 8 inches and 12 inches apart. A good rule for spacing ornamental onions is one bulb per square foot. Although ornamental onion tolerates summer drought, it should be kept moist during the growing season. The tall stems may need to be staked.
The showy pink flowers appear in early summer and lasts 2-3 weeks. It has a large umbel of densely clumped florets composed of small, 6-parted flowers and in a round cluster at the top of a naked stem. Leaves are gray-green in a basal rosette with an onion aroma and start dying back as the plant flowers.
It pairs well well with daylilies and low-growing grasses. Plant near the back of the border in groups of 5-9.
Pests, Insects, and Other Plant Problems: Overly damp conditions leave ornamental onions prone to fungal issues, including a black rot that appears on the leaves and bulbs, destroying the plant. Bulb mites and bulb rot can occur.
VIDEO Created by Elisabeth Meyer for "Edibles, Bulbs, and Houseplants" a plant identification course offered in partnership with Longwood Gardens.
- Profile Video:
- See this plant in the following landscape:
- Colorful Borders
- Cultivars / Varieties:
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- Tags:
- Cultivars / Varieties:
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- Tags:
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Attributes:
- Genus:
- Allium
- Species:
- giganteum
- Family:
- Amaryllidaceae
- Life Cycle:
- Bulb
- Perennial
- Recommended Propagation Strategy:
- Division
- Seed
- Country Or Region Of Origin:
- Himalayas, Western and Central Asia
- Play Value:
- Attractive Flowers
- Colorful
- Fragrance
- Particularly Resistant To (Insects/Diseases/Other Problems):
- Typically not susceptible to animals.
- Dimensions:
- Height: 1 ft. 0 in. - 6 ft. 0 in.
- Width: 1 ft. 0 in. - 2 ft. 0 in.
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Whole Plant Traits:
- Plant Type:
- Bulb
- Herbaceous Perennial
- Perennial
- Poisonous
- Habit/Form:
- Erect
- Growth Rate:
- Medium
- Maintenance:
- Low
- Texture:
- Medium
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Cultural Conditions:
- Light:
- Full sun (6 or more hours of direct sunlight a day)
- Soil Texture:
- Clay
- Loam (Silt)
- Sand
- Soil pH:
- Acid (<6.0)
- Alkaline (>8.0)
- Neutral (6.0-8.0)
- Soil Drainage:
- Good Drainage
- Available Space To Plant:
- Less than 12 inches
- NC Region:
- Coastal
- Mountains
- Piedmont
- USDA Plant Hardiness Zone:
- 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b
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Fruit:
- Fruit Type:
- Capsule
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Flowers:
- Flower Color:
- Pink
- Purple/Lavender
- Flower Inflorescence:
- Umbel
- Flower Value To Gardener:
- Fragrant
- Good Cut
- Good Dried
- Long-lasting
- Flower Bloom Time:
- Spring
- Summer
- Flower Shape:
- Star
- Flower Petals:
- 6 petals/rays
- Flower Size:
- < 1 inch
- Flower Description:
- The purple star-shaped flowers are small, 6-parted, and in a cluster 5-6 inches wide at the top of a naked stem. Blooms early summer in June-July and lasts 2-3 weeks. Good cut or dried.
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Leaves:
- Leaf Color:
- Blue
- Gray/Silver
- Green
- Leaf Value To Gardener:
- Fragrant
- Leaf Type:
- Simple
- Leaf Arrangement:
- Rosulate
- Leaf Shape:
- Linear
- Leaf Margin:
- Entire
- Hairs Present:
- No
- Leaf Length:
- > 6 inches
- Leaf Width:
- 3-6 inches
- Leaf Description:
- The leaves are long, slender, and strap-like, 2-3 ft. tall and 2-4 in. wide. They come up as a tight, upright cluster and then usually lie flat at the base of the plant. They have a fragrance that resembles garlic or onion. Slightly glaucous, which means that they are green with a tinge of blueish-gray. Often die down shortly after blooming has occurred.
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Stem:
- Stem Color:
- Green
- Stem Is Aromatic:
- No
- Stem Surface:
- Smooth (glabrous)
- Stem Description:
- Sturdy green stem 3-4 feet tall
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Landscape:
- Landscape Location:
- Naturalized Area
- Landscape Theme:
- Children's Garden
- Cottage Garden
- Cutting Garden
- Pollinator Garden
- Design Feature:
- Accent
- Border
- Small groups
- Attracts:
- Butterflies
- Resistance To Challenges:
- Deer
- Rabbits
- Problems:
- Poisonous to Humans
- Problem for Cats
- Problem for Dogs
- Short-lived
- Weedy
