Planting Guides
When to Plant Onions in Los Angeles: Complete Guide + Best Varieties for Zone 10b
Los Angeles, California
USDA Zone 10b
Last Frost: Feb 15
Last updated: October 30, 2025
Plant short-day onions in Los Angeles between October and December for spring harvest. Zone 10b's mild winter climate requires specific varieties that bulb with only 10-12 hours of daylight.
— Image © PlantReference.org 2026
Quick Answer
Plant short-day onions in Los Angeles October through December. They need only 10-12 hours daylight to bulb properly.
TL;DR
Plant short-day onions in Los Angeles between October and December for spring harvest. Zone 10b requires varieties like Allium cepa 'Texas Early Grano' that bulb with only 10-12 hours of daylight. Never plant long-day varieties—they won't form bulbs in Southern California's latitude.
Frequently Asked Questions
When exactly should I plant onions in Los Angeles?
Plant short-day onion transplants between mid-October and December for spring harvest. The optimal window is November 1-15 when soil temperatures are cooling but still warm enough for good root establishment. Avoid spring planting completely—Los Angeles's maximum 14.5-hour summer daylight isn't long enough to trigger bulbing in long-day varieties, and short-day types will bulb prematurely if planted in spring.
What onion varieties grow best in Los Angeles's climate?
Only short-day varieties succeed in Los Angeles. Allium cepa 'Texas Early Grano' is my top recommendation for reliable, large bulbs with sweet flavor. Allium cepa 'Red Creole' offers better storage life with stronger flavor, while Allium cepa 'Granex' produces ultra-mild Vidalia-type onions for fresh eating. Never plant long-day varieties like 'Walla Walla'—they won't bulb properly at 34°N latitude.
Why do my onions only grow green tops without forming bulbs?
This classic problem occurs when Los Angeles gardeners plant long-day onion varieties that need 15-16 hours of daylight to trigger bulbing. Los Angeles's maximum summer daylight is only 14.5 hours, so these varieties remain in vegetative growth producing green tops but no bulbs. The solution is selecting only short-day varieties bred to bulb with 10-12 hours of daylight, which occurs naturally during Los Angeles's March-April growing season.
Can I plant onion sets from the garden center in Los Angeles?
Most onion sets sold in Los Angeles garden centers are long-day varieties shipped from northern suppliers and won't produce bulbs in Southern California. If you find sets labeled as short-day varieties like 'Texas Grano' or 'Red Creole', they'll work fine planted in fall. However, transplants offer much better variety selection and reliability for Los Angeles gardeners. Choose sets smaller than a dime size—large sets tend to bolt rather than bulb.
How do I manage watering for onions in Los Angeles clay soil?
Los Angeles clay soil creates unique watering challenges because it becomes waterlogged easily but also dries to concrete hardness. Install drip irrigation for consistent, controlled watering. Water deeply but less frequently—1-2 times weekly in winter, increasing to 2-3 times as weather warms. Check soil moisture 3-4 inches deep with your finger or a soil moisture meter. Stop watering when tops begin yellowing naturally as this signals bulb maturity and prevents storage rot.
When should I harvest onions planted in Los Angeles?
Harvest when 50-75% of tops have fallen over naturally, typically April through May depending on planting date. October plantings are ready in early April, while December plantings mature in late May. Never bend tops over artificially as this stops nutrient flow to bulbs. Los Angeles's coastal humidity during May harvest requires careful curing in a shaded, well-ventilated area like a garage with fan rather than outdoor curing.
Do I need to cure onions differently in Los Angeles's climate?
Yes, Los Angeles's marine layer creates humidity during the typical May harvest period that slows proper curing. Cure harvested onions in a protected area with good air circulation rather than outdoors. A garage with a fan works better than outdoor curing when morning marine layer creates humid conditions. Proper curing takes 3-4 weeks in Los Angeles humidity versus 2-3 weeks in drier climates. Onions are fully cured when necks are completely tight and papery.
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Written By
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Emma Chen
Emma runs a small succulent propagation business from her home in San Diego, shipping starter plants and cuttings across the country. She fell into succulents after college when she realized they were the only plants that survived her travel schedule—she was working as a travel nurse at the time. San Diego's mild, dry climate is ideal for outdoor succulent gardens, and Emma's front yard is a living catalog of over 200 varieties. She completed a certificate program in ornamental horticulture and writes about succulent care, propagation techniques, and drought-tolerant garden design. Her writing is calm and reassuring—she knows people feel bad about killing plants, and she wants them to stop worrying so much.
