Planting Guides
When to Plant Onions in Miami: Complete Guide + Best Varieties for Zone 10b
Miami, Florida
USDA Zone 10b
Last updated: October 30, 2025
Plant short-day onions in Miami from November through January for spring harvest. Discover which varieties thrive in Zone 10b's frost-free climate.
— Image © PlantReference.org 2026
Quick Answer
Plant short-day onion transplants in Miami from November 15 through January 15. Texas Super Sweet and Red Creole varieties thrive in Zone 10b conditions.
TL;DR
Miami gardeners must plant short-day onions from November through January for successful spring harvest. Long-day varieties will never bulb in Miami's climate, while intermediate-day types rarely produce good bulbs. Texas Super Sweet Allium cepa 'Texas Super Sweet' and Red Creole Allium cepa 'Red Creole' are your best choices for Zone 10b's 365-day growing season. Plant transplants in December for peak spring harvest.
Frequently Asked Questions
Can I plant regular onion sets from the garden center in Miami?
Most garden center onion sets are long-day varieties that will not bulb properly in Miami's climate. These varieties need 14-16 hours of daylight to trigger bulb formation, but Miami's longest day provides only 13.5 hours. You must specifically seek out short-day varieties like Allium cepa 'Texas Super Sweet' or Allium cepa 'Red Creole' for successful bulb production in Zone 10b.
Why do my onions never form bulbs in Miami?
The most common cause is planting the wrong day-length type for Miami's latitude. Long-day onions will never bulb in South Florida because they're genetically programmed to wait for 15+ hour days that never occur at 26°N latitude. Additionally, planting too late in the season (February or later) doesn't give plants enough cool weather to develop sufficient foliage before bulbing triggers occur.
When is the latest I can plant onions in Miami?
January 15th is the absolute latest for successful bulb production. Planting later reduces the cool-weather growing period needed for foliage development. Since onions form one bulb ring for each leaf produced, late planting results in small bulbs. The optimal window is November 15 through January 15, with December being ideal.
Can I grow garlic successfully in Miami?
Garlic is challenging in Miami because it requires 4-8 weeks below 40°F (4°C) for proper clove formation. Your best option is Allium sativum 'California Early' softneck variety with pre-chilling. Store whole bulbs in the refrigerator for 6-8 weeks before planting in December. Even with this technique, expect lower yields and some "rounds" (undivided bulbs) rather than perfect segmented heads.
How do I prevent my onions from bolting in Miami?
Choose bolt-resistant short-day varieties and maintain consistent growing conditions. Allium cepa 'Texas Super Sweet' shows excellent bolt resistance. Avoid planting during cold snaps below 50°F (10°C), provide consistent moisture through drip irrigation, and ensure plants aren't stressed by heat or drought. Remove any flower stalks immediately if they appear to redirect energy into bulb development.
What's the best soil preparation for Miami onions?
Miami's sandy soils need significant organic matter additions for successful onion growing. Work 3-4 inches of compost into beds along with aged cow manure for slow-release nitrogen. Add perlite if drainage is still poor, and test pH—aim for 6.0-6.8. Most Miami soils run alkaline, so you may need sulfur to lower pH. The key is creating moisture-retentive soil that still drains well.
How long will my Miami onions store after harvest?
Short-day varieties have limited storage life compared to northern storage onions. Allium cepa 'Texas Super Sweet' stores 1-2 months maximum, while Allium cepa 'Red Creole' may last 3-4 months under ideal conditions. The high water and sugar content that makes them sweet also makes them prone to spoilage. Plan to use fresh, dehydrate, or freeze most of your harvest rather than expecting long-term fresh storage.
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M
Maria Santos
Maria is a tropical plant grower in Miami who maintains a half-acre property packed with palms, fruit trees, and tropical ornamentals. She grew up in Puerto Rico surrounded by tropical plants and moved to South Florida for college, earning a biology degree. Maria worked at a major tropical botanic garden for several years before transitioning to freelance writing and consulting. She specializes in tropical fruit growing, hurricane-resilient landscaping, and the particular challenges of gardening in South Florida—salt air, limestone soil, intense rain, and the threat of tropical storms. Maria's practical about the realities of tropical gardening: it's not paradise if you don't understand what you're dealing with.
