If you have spent June, July, and August mostly watching rain pound your garden beds while the heat turns everything into a sauna, September is the month when hope starts creeping back. I call it Florida's second spring because that is exactly what it feels like — the same excitement, the same sense of possibility, the same rush of seed packets piling up on the counter. At Wholly Water Farms, September is when the planning notebooks come back out and the indoor seed-starting trays get filled again.

Temperatures are still high. Make no mistake about that. We are looking at daytime highs in the low 90s for most of Central Florida, and nighttime lows that refuse to dip below 75 until mid-October at the earliest. But the day length is shortening noticeably, the angle of the sun is shifting, and certain crops do not need cool air to germinate — they just need you to get started on time.

What Should You Plant in Florida in September?

September is primarily a seed-starting month, not a direct-planting month. Start cool-season crops indoors where you can control temperature and moisture, aiming to transplant outdoors in mid to late October when temperatures moderate. According to UF/IFAS, the target outdoor planting date for most cool-season vegetables in Central Florida is around October 15, which means starting seeds indoors in early to mid-September gives transplants four to six weeks to develop strong root systems before going out.

September Indoor Seed-Starting Table

Crop	Start Indoors	Transplant Outdoors	Days to Harvest	Notes
Broccoli	Early Sep	Mid-Oct	70-100	Start 6-8 weeks before transplant date
Cauliflower	Early Sep	Mid-Oct	75-100	More heat-sensitive than broccoli
Cabbage	Early Sep	Mid-Oct	70-90	Choose heat-tolerant varieties for early fall
Collards	Early Sep	Oct	60-80	Most heat-tolerant of the brassicas
Kale	Early Sep	Oct	55-75	Lacinato and Red Russian do well
Brussels Sprouts	Early Sep	Mid-Oct	90-120	Challenging in FL; needs coolest weather
Lettuce	Mid-Sep	Late Oct	45-60	Heat-tolerant varieties like Jericho

How Do You Start Seeds Indoors in Florida's Heat?

The challenge with September seed starting in Florida is that ambient temperatures inside most homes still hover around 76 to 80 degrees, even with air conditioning. Most cool-season brassicas germinate best between 65 and 75 degrees Fahrenheit, so you are right on the edge. The good news is that germination temperature requirements are more forgiving than growing temperature requirements. Seeds will germinate at 80 degrees — they just do it faster and sometimes less uniformly than at cooler temps.

I use a simple setup: standard 72-cell seed trays filled with a quality seed-starting mix, placed on a wire shelf under LED shop lights in our climate-controlled grow room. The lights run 14 hours per day, positioned about 4 inches above the soil surface. I mist the trays twice daily and cover them loosely with humidity domes until germination, then remove the domes once seedlings emerge. The key detail most people miss is airflow — a small oscillating fan running on low nearby strengthens stems and reduces the risk of damping off, which is a serious concern in Florida's humidity.

What Are Cover Crops and Why Do Depleted Summer Beds Need Them?

After a full Florida summer, your garden beds are tired. Between the intense heat, torrential rains leaching nutrients, and the general biological onslaught of a subtropical growing season, soil organic matter is depleted and structure has degraded. Cover crops are the remedy. They are plants grown not for harvest but specifically to restore soil health — adding nitrogen, building organic matter, suppressing weeds, and preventing erosion.

For Florida in September, two cover crops stand out. Sunn hemp (Crotalaria juncea) is a tropical legume that thrives in heat, grows rapidly to 6 feet or more, and fixes substantial atmospheric nitrogen into the soil through root nodule bacteria. Research from UF/IFAS shows sunn hemp can produce up to 7,000 pounds of biomass per acre in just 60 days and fix 70 to 114 pounds of nitrogen per acre. That is free fertilizer manufactured by the plant itself. Cowpea (Vigna unguiculata) is another excellent option that tolerates a wide range of soil conditions, produces 3,000 to 5,000 pounds of biomass per acre, and also fixes nitrogen as a legume.

Plant either crop in beds you will not need until November or December. When you are ready to plant those beds, cut the cover crop at the base, chop the material roughly, and either work it into the top few inches of soil or leave it as mulch on the surface. Give it two to three weeks to break down before planting into those beds.

How Do You Rejuvenate Soil After Florida Summer?

Beyond cover crops, September is the month to rebuild your soil for fall. Start by testing your soil pH — Florida's sandy soils tend to drift acidic over time, especially after heavy summer rains. Most vegetables prefer a pH between 6.0 and 6.8. If your test shows you have dipped below 5.8, a light application of dolomitic lime will correct both pH and add magnesium and calcium.

Add 2 to 3 inches of quality compost to every bed you plan to plant this fall. I make my own compost year-round from kitchen scraps, spent microgreens growing media, and yard waste, but bagged compost from a reputable source works fine too. Work it into the top 6 inches of soil along with a balanced organic granular fertilizer. The compost feeds soil biology, improves water retention in sandy soil, and provides slow-release nutrition that chemical fertilizers cannot replicate.

If you mulched heavily during summer, pull back any remaining mulch from the beds, amend the soil, and then re-mulch after planting. Layers of decomposing mulch on top of unamended soil can create a nitrogen-negative zone that starves new transplants.

What Can You Direct-Seed Outdoors in September?

A few heat-tolerant crops can go directly into the ground in September, even with temperatures still elevated. Southern peas and lima beans handle the heat fine if you keep them watered through dry spells. Okra planted now will produce through November. Quick-growing radishes can go in starting mid-September in shaded or partially shaded locations — they bolt fast in full sun heat, but a shade cloth at 30 to 40 percent can make them viable.

The indoor growers among us have it easier. Microgreens remain completely indifferent to the season. I am growing the same sunflower, radish, and pea shoot trays in September that I grow in February. That consistency is one of the things that drew me to indoor growing in the first place, and it continues to be the backbone of what we do at Wholly Water Farms.

September Garden Maintenance Checklist

Beyond planting and soil work, September has a maintenance rhythm of its own:

Clean and sanitize seed trays from previous seasons with a dilute bleach or hydrogen peroxide solution before reuse
Inventory seeds and order anything you need for fall — popular varieties sell out fast
Check irrigation systems that have been under heavy use all summer for leaks, clogged emitters, and timer accuracy
Scout for nematodes if you noticed wilting or stunted plants this summer — root knot nematodes are endemic in Florida sandy soils
Plan crop rotation so that fall brassicas do not go into beds where you grew brassicas last fall
Sharpen tools and repair structures before the busy planting season hits in October

September may still feel like summer outside, but inside the planning notebook, it is already fall. Get your seeds started now, heal your soil, and by the time October rolls around you will have strong transplants ready for the garden and amended beds ready to receive them. Florida's second spring rewards the growers who prepare.

Frequently Asked Questions

Is it too hot to plant anything outside in Florida in September?

Not entirely. Heat-tolerant crops like southern peas, lima beans, and okra can be direct-seeded outdoors in September. However, most cool-season crops should be started indoors where temperatures are controlled, then transplanted outdoors in mid to late October. Radishes can go in mid-September with shade cloth protection. The key is matching plant heat tolerance to the conditions rather than forcing cool-season crops into hot soil.

How long should cover crops grow before you turn them under?

Cover crops like sunn hemp and cowpea need 45 to 60 days of growth to produce meaningful biomass and fix significant nitrogen. Plant them in early September and cut them down in late October or November before they set seed. Chop the material and either work it into the top few inches of soil or leave it as surface mulch. Allow two to three weeks of decomposition before planting into those beds.

Can I start tomato seeds indoors in September for fall planting?

Yes, and you should. September is the ideal time to start tomato seeds indoors for Florida's fall growing season. Choose determinate or semi-determinate varieties bred for Florida conditions, such as Solar Fire, Florida 91, or BHN 602. Transplant outdoors in mid to late October once nighttime temperatures begin dropping below 75 degrees. Fall tomatoes can be among the best you grow all year because the cooler weather during fruit set improves flavor and yield.

What is the best way to test my soil before fall planting?

The UF/IFAS Extension soil testing lab offers affordable, comprehensive soil analysis through your local county Extension office. Collect samples from several spots in each bed, mix them together, and submit through the Extension office. Results typically come back in one to two weeks and include pH, nutrient levels, and specific amendment recommendations for your intended crops. Test in early September so you have time to amend before October planting.