If you garden anywhere north of Florida, September means winding down. Pulling spent tomato plants. Mulching beds for winter. But here in Zone 9a/9b, September is the opposite. It's our second spring — the moment when the growing season cracks wide open again after months of heat-soaked survival mode.

I wait for this month all summer. While the rest of the country watches leaves turn, we're filling trays with broccoli seeds and testing soil pH. The air still hangs at 90 degrees most afternoons, but the days are getting shorter. The light is shifting. And the plants know it before we do.

What Cool-Season Crops Can You Plant in Florida in September?

September opens the window for nearly every cool-season vegetable that struggles in our summer furnace. According to UF/IFAS Extension guidance for Central Florida, the ideal planting date for many fall crops is around September 15, with North Florida gardeners starting about two weeks earlier and South Florida growers waiting until early October. Here's what goes in the ground or into seed trays this month:

Direct sow outdoors: radishes, carrots, beets, lettuce (leaf varieties), Swiss chard, collards, mustard greens, turnips, and beans. These seeds germinate fast in the warm September soil — typically within 3-7 days — and the heat actually helps them establish strong root systems before cooler weather arrives.

Start indoors for October transplant: broccoli, cauliflower, Brussels sprouts, cabbage, kale, and celery. These brassicas need 4-6 weeks of indoor growing before they're ready for the garden. Start them now in cell trays under lights, and they'll be stocky transplants by mid-October when nighttime temperatures finally start dropping into the 60s and 70s.

Transplants you can set out now: eggplant, peppers, and tomatoes (if you can find heat-tolerant varieties) still have time for a fall harvest. Look for determinate tomato varieties that will set fruit quickly before the first potential cold snap in December or January.

How Should You Prepare Your Soil After a Florida Summer?

Summer in Florida does a number on garden soil. Months of daily rain leach nutrients downward, and the intense microbial activity in the heat burns through organic matter faster than you can add it. Before planting a single seed, spend the first week of September on soil recovery.

Start with a pH test. Florida soils tend to drift toward the alkaline side thanks to our limestone bedrock and alkaline irrigation water, but heavy summer rains can sometimes push sandy soils acidic. Most vegetables prefer a pH between 6.0 and 6.8. A simple test kit from your county extension office costs nothing and saves you from guessing.

Next, work in 2-3 inches of quality compost. Our sandy soil has almost no organic matter naturally — maybe 1-2% if you've been amending consistently. Compost adds both nutrients and water-holding capacity, which matters when October and November bring those stretches of zero rainfall. I also add a balanced organic granular fertilizer (something like a 4-4-4) at planting time and side-dress with fish emulsion every two to three weeks once plants are established.

If nematodes were a problem this past summer — and in Florida, they almost always are — consider solarizing empty beds for two weeks before planting. Lay clear plastic tight against moist soil and let the September sun cook the top few inches. It won't eliminate every nematode, but it knocks populations back significantly.

What About the Heat? Can Seedlings Survive 90-Degree September Days?

This is the question I get most from newer Florida gardeners. Yes, it's still brutally hot. Afternoon temperatures regularly hit 90-92 degrees Fahrenheit through the end of September. But here's what matters more than the peak temperature: day length is shrinking. By late September, we're losing nearly two minutes of daylight per day. That shortening photoperiod triggers hormonal changes in plants that signal the shift toward the cool season.

For newly planted seeds and transplants, provide afternoon shade during the first two weeks. A piece of 30-50% shade cloth propped on stakes works perfectly. Water in the morning so roots are hydrated before the heat peaks. And mulch — 2-3 inches of straw or leaves around transplants keeps soil temperatures 10-15 degrees cooler than bare ground.

What Is a September Planting Schedule for Central Florida (Zone 9b)?

Here's the timeline we follow at our farm and in our own kitchen garden:

Week 1 (September 1-7): Test soil pH. Amend beds with compost. Start broccoli, cauliflower, cabbage, and Brussels sprouts seeds indoors under lights. Direct sow radishes and leaf lettuce in afternoon-shaded beds.

Week 2 (September 8-14): Direct sow carrots, beets, and Swiss chard. Start kale and collard seeds indoors (or direct sow if temps are trending downward). Set out any remaining warm-season transplants like peppers and eggplant.

Week 3 (September 15-21): Direct sow beans (bush varieties for quick harvest), turnips, and mustard greens. Succession plant more lettuce and radish. Check indoor seedling trays — thin to strongest seedling per cell.

Week 4 (September 22-30): Continue succession plantings. Begin hardening off any indoor transplants that are 3-4 weeks old by setting them outside in morning light for increasing periods. Plan October planting schedule.

Can You Grow Microgreens Year-Round in Florida?

Absolutely, and this is one of the reasons we focus heavily on microgreens at Wholly Water Farms. While outdoor gardening in Florida has two distinct seasons with a brutal summer gap, microgreens grow indoors under controlled conditions 365 days a year. Temperature stays at 68-72 degrees. Humidity is managed. Light cycles are consistent.

September is actually when I tell people to start their first microgreen trays, because the excitement of fall planting often coincides with wanting to eat more fresh greens. Sunflower, radish, broccoli, and pea shoot microgreens are all ready in 7-14 days — so while you're waiting for those outdoor carrots to germinate, you can be harvesting trays of nutrient-dense greens from your kitchen counter. Check out our growing guides for step-by-step instructions.

September in Florida is about momentum. The summer rest is over. The soil is ready. And for the next six months, we get to grow the crops that make fall and winter gardening here one of the best-kept secrets in American agriculture. Get your hands dirty this week. Your December self will thank you.

Frequently Asked Questions

Is it too hot to plant vegetables in Florida in September?

No. While afternoon temperatures still reach 90 degrees Fahrenheit, shortening day length signals the shift toward cooler weather. Start heat-sensitive transplants like broccoli and cauliflower indoors, and direct sow hardy crops like radishes and lettuce with afternoon shade cloth protection for the first two weeks.

What is the best lettuce variety for Florida fall planting?

Leaf lettuce varieties like Black Seeded Simpson, Red Sails, and Buttercrunch perform best in early fall Florida conditions. They tolerate heat better than head lettuce varieties and mature in 45-60 days. Avoid iceberg types until November when nighttime temperatures drop consistently below 65 degrees.

When should I start broccoli seeds indoors in Florida?

Start broccoli seeds indoors in early September (around September 1-7) for transplanting outdoors in mid-to-late October. Broccoli seedlings need 4-6 weeks of indoor growth to develop strong stems and root systems. Use a seed-starting mix, provide 14-16 hours of light, and keep temperatures between 65-75 degrees for best germination.

How do I fix Florida soil pH for fall vegetables?

Test your soil pH first through your county extension office or with a home test kit. Most fall vegetables prefer pH 6.0-6.8. If your soil tests alkaline (above 7.0), work in elemental sulfur or acidifying organic matter like pine bark fines. If it's too acidic (below 5.5), add dolomitic lime. Amend at least two weeks before planting to allow pH to stabilize.