Growing onions in zone 10
Bulbing is triggered by day length: long-day varieties for the North, short-day for the South, intermediate in between — the wrong type simply won’t bulb. Sets are easiest; transplants give bigger bulbs.
Zone 10 covers south Florida, coastal Southern California, low desert — frost is rare — the calendar flips, with the main garden running fall through spring. Zone dates are medians: frost timing varies within a zone with elevation and terrain, so treat these windows as a solid default and refine them with your own city’s dates below.
Make it local
These windows use zone 10's typical frost dates (last frost ~Jan 25, first frost ~Dec 20). For windows computed from your frost dates, run the ZIP code frost lookup and open the planting calendar — it remembers your city. The seed starting scheduler turns the whole seed rack into one printable, date-sorted list.
Frequently asked questions
When do I plant onions in zone 10?
Transplant Dec 14 – Dec 28, counted from zone 10's typical last frost around Jan 25. As a hardy crop it tolerates the light frosts on either side of that window.
When should I start seeds indoors for onions in zone 10?
Sow indoors Nov 16 – Nov 30 — that's 10 to 8 weeks before the typical Jan 25 last frost, giving sturdy transplants exactly when the garden is ready for them.
Can I direct sow onions in zone 10?
Yes — direct sow Dec 28 – Jan 11. Transplants buy a head start, but direct-sown plants catch up quickly once soil warms.