How to Grow Texas SuperSweet Onion

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Texas SuperSweet Onion

Allium cepa var. cepa

vegetable

Texas SuperSweet is a long-day onion variety prized for its exceptional sweetness and mild flavor, making it one of the most popular sweet onions grown in Texas and the southern United States. These large, globe-shaped bulbs can reach 4-5 inches in diameter and are best enjoyed fresh rather than cooked. The variety was developed by Texas A&M University and is renowned for its tender, juicy flesh and low sulfur content.

When should you plant Texas SuperSweet Onion in your zone?

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Example Texas SuperSweet Onion timeline · Pittsburgh, PA (Zone 6b)

Plant Texas SuperSweet Onion
Around Apr 17

Near Pittsburgh's average last spring frost.
Tend & protect
Late spring–summer

Watering, feeding, and pest-watch reminders.
Harvest Texas SuperSweet Onion
Around Aug 15

≈ 120 days after planting

Sample dates for Pittsburgh, PA. Sign up to get exact Texas SuperSweet Onion dates for your own zip code.

Growing Conditions

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Sun: Full sun, 8+ hours daily

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Water: Consistent moisture; 1-1.5 inches per week. Keep soil evenly moist but not waterlogged. Reduce watering as bulbs mature and approach harvest.

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Spacing: 4-6 inches

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Days to maturity: 120-150 days from transplant

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Planting depth: 0.5 inches for sets; transplants should be planted at the same depth they were growing

Soil

Type: Well-draining, fertile loamy or sandy loam soil

pH: 6.0-7.0

Amendments:

Compost aged manure balanced fertilizer (10-10-10) sulfur if pH is too high

Growing Zones

Find your zone →

Thrives in zones 8-10; performs best in South Texas and warm southern regions

8a 8b 9a 9b 10a

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Growth Stages

Transplant/Establishment

2-3 weeks

Small transplants (4-6 weeks old, pencil-thin) or sets are planted in fall (September-November in Texas). Plants develop shallow root systems and 3-4 leaves.

Harden off transplants before planting. Keep soil moist but not soggy. Mulch lightly to conserve moisture. Plant in raised beds or well-prepared soil for best drainage.

Vegetative Growth

6-8 weeks

Plants produce multiple leaves and establish bulbs begin to form as day length increases. Foliage grows tall (12-18 inches) with visible green shoots.

Apply nitrogen-rich fertilizer every 3-4 weeks. Keep soil consistently moist. Thin to proper spacing if needed. Monitor for pests and diseases. Remove any flower stalks that form.

Bulb Enlargement

6-8 weeks

Bulbs swell noticeably as photoperiod effects trigger bulbing. The characteristic globe shape becomes apparent. Foliage remains green and upright.

Maintain consistent watering and fertilization. Provide balanced fertilizer (equal N-P-K). Ensure full sun exposure. Side-dress with compost if needed. Watch for spider mites in dry conditions.

Maturation & Bulb Development

3-4 weeks

Bulbs reach full size (4-5 inches diameter). Outer layers dry and papery. Foliage gradually yellows and begins to topple over.

Reduce watering gradually to begin curing process. Stop fertilizing 2-3 weeks before harvest. Ensure good air circulation. Do not crush or damage foliage.

Harvest & Curing

2-3 weeks

Foliage dies back completely and falls over naturally. Bulbs are fully matured with dry papery skin. Ready for harvest and long-term storage.

Harvest when 50-75% of tops have fallen over. Cure bulbs in a warm, dry, well-ventilated location (75-85°F) for 2-3 weeks. Store in cool conditions with good airflow.

Companion Planting

Plan your garden →

Plant with:

Beets Carrots Chamomile Lettuce Parsnips Strawberries Tomatoes

Avoid planting near:

Asparagus Beans Peas Sage other alliums (garlic, leeks)

Common Pests

Spray with insecticidal soap or neem oil; use row covers on young transplants; remove weeds to reduce habitat; encourage beneficial insects
Increase humidity and irrigation; spray with water to dislodge mites; apply miticide or neem oil if severe; improve air circulation
Use row covers on young plants; apply beneficial nematodes to soil; remove affected bulbs; practice crop rotation
Use disease-free sets and transplants; ensure excellent drainage; avoid overwatering; remove infected plants; rotate crops
Plant resistant varieties; use well-draining soil; avoid planting onions in same location for 3+ years; sanitize tools

Uses

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Fresh eating & salads

Culinary

Texas SuperSweet onions are exceptional for fresh use, slicing into sandwiches, and adding to salads due to their natural sweetness and tender, juicy texture. Their mild flavor makes them approachable even for those who typically avoid raw onions. [source]

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Grilling & sautéing

Culinary

The high sugar content in Texas SuperSweets makes them excellent for grilling and caramelizing, developing deep, sweet flavors. They add natural sweetness to dishes without added sugar. [source]

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Quercetin & antioxidants

Medicinal

Like all onions, Texas SuperSweets contain quercetin and other polyphenols with anti-inflammatory and antioxidant properties. Regular consumption may support cardiovascular health and immune function. [source]

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Natural dye production

Household

The papery outer skins of onions can be used to create natural yellow to golden-brown dyes for fabric and fiber arts. The process is simple and produces consistent, beautiful colors. [source]

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Pollinator support

Wildlife

If allowed to bolt and flower (rare with SuperSweets), onion flowers provide nectar and pollen for bees and other beneficial insects. The delicate purple flowers attract pollinators to the garden. [source]

This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.

Harvest Tips

Harvest when 50-75% of foliage has naturally toppled over and dried, typically late May through June in Texas. Gently pull bulbs from soil or use a garden fork to loosen soil first. Leave intact with soil attached if possible. Cure bulbs in a warm (75-85°F), dry, well-ventilated location for 2-3 weeks until outer skin is papery and necks are completely dry. Trim roots to 0.5 inches and remove excess dried soil. Store in mesh bags or open containers at 50-65°F with good air circulation; Texas SuperSweets have good storage life of 2-3 months.

Fun Facts

🌱 Texas SuperSweet onions are protected by the Texas Department of Agriculture's 'Texas Sweet Onion' trademark; only onions grown in specific Texas regions (primarily the Winter Garden and Rio Grande Valley) can legally be marketed as Texas 1015 SuperSweets or similar branded varieties.
🌱 The low sulfur content in Texas SuperSweets is what gives them their mildness and sweetness—sulfur compounds are responsible for the sharp, pungent flavor of storage onions, so these sweet varieties naturally contain 50-70% less sulfur.
🌱 Texas SuperSweet onions are long-day onions that require 13+ hours of daylight to trigger bulbing, which is why they perform best in southern latitudes where longer daylight hours exist during their growing season (October-June).

Gardening Terms

New to gardening? Learn about terms used in this guide:

Compost Full Sun Mulch N-P-K pH Raised Bed Transplant

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