Florida doesn’t run one seed-starting calendar, it runs two. Around Jacksonville and the rest of north Florida, you still count backward from a real last spring frost, the way a gardener in Georgia or the Carolinas would. Cross into central and south Florida and frost mostly drops out of the picture, so the whole rhythm flips: winter turns into the main growing season and summer becomes the thing you’re protecting plants from. This calendar covers the north Florida side, where frost still sets the clock. Pin down your last spring frost window first, then work every indoor sowing date backward from it.
The date everything counts back from
Every date in this calendar is anchored to one figure: the last spring frost near Jacksonville, which NOAA’s National Centers for Environmental Information puts between February 16 and March 7, based on the 1991-2020 climate normals for the Jacksonville airport station. That’s not a typo or a hedge. It’s a thirty-year spread of when the last freeze actually showed up, and three of those thirty years saw no freeze at all. A three-week range is the honest answer, not a single date pretending to be one.
Why the range matters
Sow too early against that range and you’re gambling on the low end, February 16, arriving on schedule. If it doesn’t, and the freeze holds off until early March instead, your seedlings sit in pots for two or three extra weeks with nowhere to go. Indoors, under imperfect light, that means stretched, leggy stems and root systems circling the bottom of the cell before you ever get them outside. Sow too late against the range and you lose growing weeks at the other end, pushing crops like tomatoes and peppers into the ground behind schedule for a state where the true limiting season, for north Florida at least, is short.
The practical fix is to build your calendar off the late end of the range rather than the early one. Counting back from March 7 instead of February 16 costs you almost nothing if the freeze does come early, since seedlings started a week or two later usually still catch up. Counting back from February 16 and getting a late freeze instead costs you real setback. If you want the fuller picture of how this range compares across the rest of the state, the First and Last Frost Dates in Florida page breaks out the pattern county by county, because Jacksonville’s numbers are not Orlando’s or Miami’s.
Keep in mind, too, that this figure is a freeze probability band, not a guarantee. NOAA’s normals describe a 30 to 70 percent chance of 32°F in that window, which is why local gardeners still watch the extended forecast in late February rather than trusting the calendar alone.
The calendar, crop by crop
Once you’ve fixed the last frost range at February 16 to March 7, the University of Minnesota Extension’s standard weeks-indoors table does the rest of the arithmetic. The University of Minnesota Extension gives weeks-before-transplant figures, and they translate directly once you count them back from a local frost date instead of a Minnesota one.
| Crop | Weeks indoors before last frost | Jacksonville sowing window |
|---|---|---|
| Leeks, onions | 14-15 weeks | November 3 to November 29 |
| Celery | 12-13 weeks | November 17 to December 13 |
| Broccoli, Brussels sprouts, cabbage, cauliflower, head lettuce | 10-11 weeks | December 1 to December 27 |
| Eggplant, okra, peppers | 9 weeks | December 15 to January 3 |
| Tomatoes | 5-6 weeks | January 5 to January 31 |
| Sweet potatoes (slips) | 3-4 weeks | January 19 to February 14 |
Notice how early the list starts. Onions and leeks go into seed trays in early November, well before most gardeners are thinking about spring at all, because they need fourteen to fifteen weeks of indoor growing before they’re ready to face the ground. Tomatoes, by contrast, only need five to six weeks, which is why their sowing window doesn’t open until January. If you’ve never grown tomato seedlings indoors before, the mechanics of light and potting-up are covered in more depth in Growing Tomato Seedlings Indoors, and the same applies to head lettuce, which is worth starting from seed rather than buying as transplants if you want a particular variety: see Starting Lettuce for the specifics on that crop’s germination needs.
What not to start indoors
Not everything belongs in a seed tray. Root crops like carrots, beets, radishes and turnips do not transplant well, since disturbing the taproot at transplant time tends to fork or stunt it, so these go straight into garden soil once the frost risk has passed. Beans and squash germinate fast and resent root disturbance too, and they grow quickly enough from direct sowing that starting them indoors buys you little. The general rule among extension services is that anything with a sensitive or fast-growing root system does better sown where it will stay, while slow-starting crops with transplantable roots, like the ones in the table above, are the ones worth the extra weeks indoors. For the fuller planting-out schedule once frost risk has passed, the Florida Planting Calendar lays out transplant and direct-sow dates side by side.
Light, warmth and hardening off
A windowsill in a Florida winter looks bright to the eye, but it’s rarely bright enough for a seedling, and even a south-facing sill delivers light from one direction only. Seedlings reaching for that single light source grow tall and thin fast, with weak stems that flop over before they ever see soil outdoors. That’s the classic leggy-seedling problem, and it shows up hardest on the crops that spend the longest indoors, onions and celery among them, simply because they have more weeks to stretch.
Germination itself asks for something different: steady, even warmth at the soil level rather than bright light. Most of these crops germinate in the dark or under low light and only need strong light once the first true leaves appear, so a warm, out-of-the-way spot for the seed tray in the first days after sowing matters more than a sunny window at that stage.
Before anything goes into garden soil, it needs to toughen up. The University of Minnesota Extension’s guidance, the same source behind the weeks-indoors table above, recommends hardening off over the final one to two weeks before transplanting, moving trays outside for a little longer each day so the seedlings adjust to direct sun, wind and the temperature swing between day and night. Skip that step and even a healthy, stocky seedling can scorch or wilt within a day of being set out.
What goes wrong
The most common mistake is simply starting too early against the whole point of the range: sowing tomatoes or peppers in November because the weather already feels mild, then watching them outgrow their pots weeks before the ground and the frost risk are actually ready for them. The fix is sticking to the sowing window in the table above rather than starting the moment the impulse hits.
Damping off is the second one, a fungal problem that rots seedlings at the soil line within days of germination, usually because trays are overwatered, crowded, or sitting in poor air circulation. It shows up as seedlings that look fine one day and are collapsed and dark at the stem base the next. Thin sowing, letting the surface dry slightly between waterings, and reasonable airflow around the trays are what keep it from starting in the first place.
The third mistake happens after the seedlings leave the house: planting out right at the early edge of the frost range, February 16, and getting caught by a freeze that shows up on the late end instead. Since NOAA’s normals describe a genuine spread rather than a hard cutoff, treating March 7 as the safer target for tender crops like tomatoes, peppers and eggplant costs little and protects against the years the freeze runs late.
Gardeners moving to Florida from a harsher climate sometimes assume the seed-starting weeks themselves must be different here too. They aren’t. The University of Minnesota Extension’s table of weeks-indoors is the same one referenced for Minnesota’s own crop-by-crop seed-starting calendar. What changes state to state, and what actually does the work of localizing this calendar, is the last spring frost date it counts back from, not the weeks themselves. For more on how the rest of Florida’s growing calendar hangs together outside the seed-starting window, the Florida guides hub covers the broader state picture, since Jacksonville’s numbers apply mainly to the northern part of the state.
Common questions
Can I just start seeds indoors year-round since Florida is warm?
Not around Jacksonville, no. North Florida still gets a real last spring frost between February 16 and March 7 by NOAA’s normals, so tender crops sown indoors too early just sit in pots waiting on the calendar. Central and south Florida run on a different, frost-free rhythm where winter is the main season, but that inverted calendar doesn’t apply this far north.
What if my winter didn’t have a hard freeze at all?
It happens. NOAA’s own data for the Jacksonville station shows about three years in thirty with no freeze recorded. That doesn’t mean the range is wrong, it means some years land on the mild edge of a genuine spread. Plan against the full February 16 to March 7 window rather than last year’s particular winter.
I missed my sowing window. Can I still direct sow instead?
For some crops, yes. Fast growers like beans and squash are usually direct-sown anyway and don’t lose much by skipping the indoor stage. Slow crops like onions, celery and cabbage lose real time if sown late outdoors instead of indoors, since they were given that many weeks’ head start for a reason, so a late transplant purchased locally is often a better fix than direct sowing them at that point.
Does this calendar work for Orlando or Miami?
No. The frost figures here come specifically from the Jacksonville station and describe north Florida. Central and south Florida are effectively frost-free by NOAA’s data, and the growing calendar there runs on the opposite schedule, with winter as the main season and summer as the difficult stretch, so this window should not be applied south of north Florida.