Growing onions in zone 9
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 9 covers gulf Coast, central Florida, central California, Phoenix and Tucson — summer heat is the limiting factor — many "spring" crops grow best in fall and winter. 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 9's typical frost dates (last frost ~Feb 20, first frost ~Dec 1). 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 9?
Transplant Jan 9 – Jan 23, counted from zone 9's typical last frost around Feb 20. 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 9?
Sow indoors Dec 12 – Dec 26 — that's 10 to 8 weeks before the typical Feb 20 last frost, giving sturdy transplants exactly when the garden is ready for them.
Can I direct sow onions in zone 9?
Yes — direct sow Jan 23 – Feb 6. Transplants buy a head start, but direct-sown plants catch up quickly once soil warms.