What are the sun requirements for Allium cepa 'Superstar'?

Allium cepa 'Superstar' requires full sun.

How much water does Allium cepa 'Superstar' need?

Allium cepa 'Superstar' has moderate with consistent moisture during growing season water needs.

Allium cepa 'Superstar', Superstar Onion

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Annuals

Allium cepa 'Superstar'

Superstar Onion

AmaryllidaceaeAsia

At a Glance

Typeannual

Habitupright

Foliagedeciduous

Height24-36 inches

Width6-8 inches

Maturity0.42 years

Key Features

Deer Resistant

Fragrant (strong)

Container Friendly

Maintenancelow

Overview

Allium cepa 'Superstar' is an exceptional large-bulb onion cultivar that stands out for its impressive size and outstanding flavor profile. This annual vegetable crop produces magnificent globe-shaped bulbs that regularly reach 4-6 inches in diameter, making them among the largest storage onions available to home gardeners. The bulbs feature attractive golden-bronze papery outer scales that protect the crisp, white interior flesh arranged in perfect concentric rings. The foliage emerges as distinctive hollow, cylindrical leaves that display an attractive blue-green color with a waxy surface texture. These tubular scapes grow in an upright, fountain-like arrangement directly from the underground bulb, typically reaching 24-36 inches in height and creating an architectural presence in the garden. When environmental stress triggers bolting, Allium cepa 'Superstar' produces impressive flower stalks that can tower 4-5 feet tall, topped with dense, perfectly spherical umbels of small white star-shaped flowers. The entire plant emits the characteristic sharp, pungent onion fragrance when disturbed, and this cultivar is particularly noted for its mild, sweet flavor that makes it excellent for both fresh eating and cooking applications.

Native Range

Allium cepa originates from the mountainous regions of central Asia, specifically areas that encompass modern-day Iran, Afghanistan, Pakistan, and adjacent territories. Wild forms of the species can still be found growing naturally in these highland areas, where they have adapted to well-draining soils and seasonal temperature fluctuations. The species has been under cultivation for over 5,000 years, spreading from its Asian homeland throughout the ancient world via established trade routes.

Suggested Uses

Allium cepa 'Superstar' excels in traditional vegetable gardens, raised bed systems, and even large container plantings where space allows. The impressive size of the mature bulbs makes this cultivar particularly valuable for culinary applications where substantial onion presence is desired, such as stuffing whole onions, roasting for caramelized preparations, or featuring prominently in soups and stews. The mild, sweet flavor profile makes it excellent for fresh applications including salads, sandwiches, and raw preparations. Due to its exceptional storage qualities, it's an ideal choice for gardeners wanting to grow their own supply of cooking onions for winter use. The remarkable size potential also makes this cultivar popular among exhibition growers and those participating in county fair competitions.

How to Identify

Allium cepa 'Superstar' can be reliably identified by several distinctive characteristics that set it apart from other garden plants. The most obvious feature is the hollow, cylindrical blue-green foliage that grows directly from the underground bulb without any visible above-ground stem structure. These tubular leaves have pointed tips and a distinctive waxy surface that helps distinguish them from solid-stemmed plants. The mature bulbs are exceptionally large, typically measuring 4-6 inches in diameter with a classic globe shape and golden-bronze papery outer scales. If the plant bolts to flower, it produces tall, sturdy stalks topped with perfectly round clusters of small white flowers arranged in dense umbels. The entire plant releases an unmistakable sharp, pungent onion aroma when any part is crushed, cut, or bruised, providing immediate confirmation of identification.

Appearance

Size & Dimensions

Height2' - 3'

Width/Spread6" - 8"

Reaches mature size in approximately 0.42 years

Colors

Flower Colors

white

Foliage Colors

blue

green

Fall Foliage Colors

yellow

Bloom Information

Bloom Period

Summer

mid to late summer when bolting occurs

Detailed Descriptions

Flower Description

white

Foliage Description

blue-green with waxy texture

Growing Conditions

Sun Requirements

Full Sun

• 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 - 7.0(Neutral)

357912

Soil Types

loam

Drainage

well drained

Water & Climate

Water Needs

moderate with consistent moisture during growing season

Time to Maturity

4-5 months from planting

Care & Maintenance

Care Guide

Allium cepa 'Superstar' thrives in well-draining, fertile soil that has been amended with generous amounts of compost or well-aged manure to provide sustained nutrition throughout the growing season. Plant in a location that receives full sun exposure for optimal bulb development and size. Maintain consistent soil moisture during active growth, but be careful to avoid overwatering which can lead to bulb rot and disease issues. Apply a balanced fertilizer when plants reach 6 inches in height, then provide a second feeding when the bulbs begin to noticeably swell. As the growing season progresses and tops begin to yellow naturally, gradually reduce watering frequency. Stop irrigation completely when the foliage starts to fall over, signaling that the bulbs are ready for harvest. After harvesting, cure the bulbs in a warm, dry, well-ventilated location for 2-3 weeks before moving to long-term storage.

Pruning

Allium cepa 'Superstar' requires very little pruning during its growing cycle, but timing is crucial for optimal bulb development. Remove any flower stalks (scapes) that appear as soon as they emerge, unless you specifically want to collect seeds, because flowering redirects the plant's energy away from bulb formation and can significantly reduce final size. Resist the temptation to cut back or trim the foliage during the growing season, even if it looks untidy, as these leaves are actively photosynthesizing and feeding the developing bulb underground. Only when the tops naturally begin to yellow and topple over should you consider cutting them. At harvest time, the dried tops can be braided together for attractive storage, or cut back to leave about 1 inch of stem above the bulb for loose storage in mesh bags or crates.

Maintenance Level

low

Container Growing

✓ Suitable for container growing

Minimum container size: 5 gallons

⚠️ Toxicity Warning

Allium cepa 'Superstar' is safe for human consumption when properly prepared, though sensitive individuals may experience digestive upset from raw onions, particularly in large quantities. All parts of the plant contain compounds that are toxic to dogs, cats, and many other pets, potentially causing serious health issues including anemia and severe gastrointestinal problems. Keep pets away from both the growing plants in the garden and harvested bulbs during storage and food preparation to prevent accidental ingestion.

Planting Guide

Planting Methods & Timing

Planting Method

both

Indoor Start

10 weeks before last frost

Direct Sow Timing

early spring, 2-4 weeks before last frost date

Days to Maturity

110–130 days

Plant Spacing

4 inches

Companion Planting

Good Companions

tomatoes

peppers

carrots

brassicas

lettuce

Avoid Planting With

beans

peas

asparagus