What hardiness zones is Allium 'Red Giant' suitable for?

Allium 'Red Giant' is suitable for USDA hardiness zones 5, 6, 7, 8.

What are the sun requirements for Allium 'Red Giant'?

Allium 'Red Giant' requires Full Sun.

How much water does Allium 'Red Giant' need?

Allium 'Red Giant' has Low water needs.

Allium 'Red Giant', Red Giant Ornamental Onion

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Bulbs

Allium 'Red Giant'

Red Giant Ornamental Onion

Amaryllidaceae

Central Asia (Allium hybrid; Red Giant; largest deep reddish-purple umbel 6-8 in; architectural seed heads; deer/rodent resistant; foliage dies back at bloom; z5)

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At a Glance

TypeBulb

HabitUpright

FoliageDeciduous

Height36-48 inches (90-120 cm)

Width12-18 inches (30-45 cm)

Maturity1 years

Growing Zones

USDA Hardiness Zones

5 - 8

Zone 5 Zone 6 Zone 7 Zone 8

These zones indicate the coldest temperatures this plant can typically survive.

What's my zone? →

Frost Tolerancehardy

Key Features

Attracts Pollinators Attracts Butterflies Deer Resistant Drought Tolerant Container Friendly

Maintenancevery low

Overview

Allium 'Red Giant' is a bulbous perennial reaching 36-48 inches (90-120 cm) tall with a spread of 12-18 inches (30-45 cm) and an upright habit with a single, stiff, leafless flower stem (scape) rising from a basal rosette of strap-like leaves. A hybrid ornamental onion, it produces large, dense, spherical umbels 6-8 inches (15-20 cm) in diameter composed of hundreds of small star-shaped, deep reddish-purple to violet-purple flowers on a sturdy scape. Among the largest-flowered ornamental alliums. Blooms in late spring to early summer. Foliage begins to yellow and die back as flowers open—a characteristic of large-flowered alliums that requires planning for companion plants to mask the fading leaves. Hardy to zone 5. Bulbs are large, 4-6 inches (10-15 cm) in circumference. Growth rate is moderate.

Native Range

Allium species from which 'Red Giant' was hybridized originate in Central Asia. 'Red Giant' is a hybrid cultivar.

Suggested Uses

Grown in perennial borders, cottage gardens, and mixed plantings for ornamental use. Among the largest-flowered ornamental alliums. Deep reddish-purple 6-8 inch spheres. Architectural dried seed heads. Deer and rodent resistant (allium). Late spring focal point. Pollinator-visited. Not suitable as standalone planting—fading foliage needs companion plant screening. Requires fall planting. Slow to naturalize.

How to Identify

Distinguished from A. 'Globemaster' by the deeper reddish-purple (versus violet-purple) color. Distinguished from A. giganteum by the larger umbels (6-8 versus 4-6 inches), the sturdier stems, and the hybrid vigor. Distinguished from drumstick allium (A. sphaerocephalon) by the much larger umbel (6-8 versus 1-2 inches) and the spherical (versus oval) shape. Red Giant—largest deep reddish-purple umbel, 6-8 inches, single stiff scape, foliage dies back at bloom, hybrid.

Appearance

Size & Dimensions

Height3' - 4'

Width/Spread1' - 1'6"

Reaches mature size in approximately 1 years

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~3 weeks

Spring

Large dense spherical umbels 6-8 inches (15-20 cm) in diameter of deep reddish-purple to violet-purple star-shaped flowers in late spring to early summer (May-June). Bloom lasts 2-3 weeks. Dried seed heads persist and remain architecturally interesting through summer and fall.

Detailed Descriptions

Flower Description

Deep reddish-purple to violet-purple; dense spherical umbels 6-8 inches; late spring

Foliage Description

Grey-green; broad strap-like; basal rosette; yellows at bloom time

Growing Conditions

Sun Requirements

Full Sun

Requires 6-10 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.0 - 7.5(Neutral)

357912

Soil Types

loam sand

Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Time to Maturity

Blooms first spring after fall planting

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Plant bulbs in fall, 6-8 inches (15-20 cm) deep and 8-12 inches (20-30 cm) apart. Full sun, well-drained soil (pH 6.0-7.5)—good drainage critical to prevent bulb rot. Plant among perennials that will mask the yellowing foliage (hostas, daylilies, hardy geraniums). Minimal care once established. Leave dried seed heads for winter architecture or cut for dried arrangements. Bulbs naturalize slowly.

Pruning

Allow foliage to yellow and die back naturally—it feeds the bulb for next year's bloom. Do not cut foliage until completely brown. Leave seed heads for architectural interest or remove after browning.

Maintenance Level

very low

Container Growing

✓ Suitable for container growing

Minimum container size: 5 gallons

⚠️ Toxicity Warning

Toxic to pets