Fall might feel far off in the heat of August, but now is the perfect time to get a head start on your cool-season vegetable garden by starting seeds indoors. In Central Mississippi (Zone 8b), the window for fall planting is short—and indoor seed starting gives you a leg up on the season.
Here’s everything you need to know to get your fall crops off to a strong, healthy start!
Why Start Seeds Indoors in August?
Many cool-season vegetables—like broccoli, cabbage, cauliflower, kale, and Brussels sprouts—prefer cooler temperatures but take several weeks to mature. By starting them indoors now, you can:
- Beat the heat while they germinate
- Transplant healthy seedlings once the worst of the summer passes
- Enjoy a longer harvest window before winter frost
What to Start Indoors Now
- Cauliflower
- Brussels Sprouts
- Cabbage
- Head Lettuce
- Broccoli
For best success, choose varieties labeled as “heat-tolerant” or “early maturing” to better handle the transition to the garden.
What You’ll Need
Starting seeds indoors doesn’t require a fancy setup—just a few basic tools and a little care:
- Seed trays or small pots with drainage holes
- Seed-starting mix (lighter than potting soil)
- Grow light or sunny windowsill (6–8 hrs/day)
- Humidity dome or plastic wrap (optional, helps with germination)
- Labels to keep track of what you’ve planted
- Watering can or spray bottle
Step by Step Guide
- Fill trays or pots with damp seed-starting mix.
- Plant seeds according to depth on the seed packet (usually ¼"–½").
- Mist gently and cover trays loosely with plastic to hold in humidity.
- Keep warm—most fall veggies germinate best at 65–75°F.
- Remove cover once sprouts appear and move to a sunny spot or under a grow light.
- Water carefully—keep soil evenly moist but not soggy.
- Thin seedlings once they develop their first set of true leaves, leaving the strongest in each cell.
Use a liquid organic fertilizer, like fish emulsion, every 10–14 days once seedlings have sprouted.
Rotate your trays daily if using window light to prevent leaning.
If you're starting leafy greens like lettuce or spinach, consider succession planting—start a few trays every 2–3 weeks for continuous harvests.
When to Transplant Outdoors
In Central Mississippi, transplant seedlings 4–6 weeks after sowing, once they have 3–5 healthy leaves and the outdoor temps begin to cool–daytime highs consistently stay below 85°F, and nights start cooling into the 60s. In our area this usually means:
- Late September to early October for broccoli, cabbage, and cauliflower
- Early to mid-October for kale and lettuce
Gradually expose them to outdoor conditions for 5–7 days before planting out. This is called hardening.
Direct Sow in August:
Don’t forget you can also direct sow some of your fall crops now. Turnips (roots & greens), Mustard Greens, Collard Greens, Kale (late August), Swiss Chard, Bok Choy/Pak Choi, Radishes.
Remember to keep soil moist and mulch around where seeds are planted to help retain moisture in the soil. Do not mulch over top where seeds are planted. Wait until seedlings have sprouted and developed true leaves before mulching around them, but not over them.
Whether you're a seasoned gardener or trying this for the first time, we have everything you need to get started—and we’re happy to answer your questions. Come see us at Callaway’s to get expert advice on prepping for your fall garden!