September in Wisconsin brings cooler temperatures that favor cold-hardy greens and root vegetables for a successful fall garden. If you’re searching for the best vegetables to plant in September in Wisconsin, you’ve come to the right place. This guide covers exactly what to sow now for a bountiful harvest before the first hard frost.
Wisconsin’s fall growing season is short but productive. With average first frost dates ranging from late September in the north to mid-October in the south, you need quick-maturing crops. The key is choosing vegetables that thrive in cool soil and tolerate light frosts.
Let’s get straight to the list. These vegetables are proven winners for September planting in Wisconsin’s climate.
Best Vegetables To Plant In September In Wisconsin
Here are the top choices that will grow well in Wisconsin’s September conditions. Each vegetable is selected for its cold tolerance and fast maturity.
Leafy Greens For Quick Harvests
Leafy greens are your best bet for September planting. They grow fast and taste sweeter after a light frost.
- Spinach – Matures in 30-45 days. Plant seeds 1/2 inch deep in rich soil. Spinach can survive temperatures down to 20°F.
- Kale – Ready in 50-60 days. It actually improves in flavor after frost. Space plants 12 inches apart.
- Lettuce – Choose loose-leaf varieties like Black Seeded Simpson or Oakleaf. Harvest in 40-50 days.
- Arugula – Ready in just 20-30 days. Sow every two weeks for continuous harvest.
- Swiss Chard – Matures in 50-60 days. It’s more cold-hardy than lettuce and colorful too.
These greens grow best when soil temperatures are between 50°F and 65°F. September soil in Wisconsin is ideal for this.
Root Vegetables That Store Well
Root vegetables are another excellent choice. They develop sweet flavor as soil cools.
- Radishes – Fastest crop at 20-30 days. Plant seeds 1/2 inch deep, thin to 1 inch apart.
- Turnips – Ready in 40-50 days. Both roots and greens are edible. Plant in full sun.
- Beets – Mature in 50-60 days. Soak seeds overnight before planting to speed germination.
- Carrots – Need 60-70 days. Choose short varieties like Danvers or Nantes for faster growth.
- Parsnips – Take 100-120 days but can stay in ground over winter. Plant now for spring harvest.
Root vegetables need loose, well-drained soil. Remove rocks and clumps before planting to prevent forked roots.
Brassicas For Fall Flavor
Brassicas, or cabbage family crops, thrive in cool weather. They are among the best vegetables to plant in September in Wisconsin.
- Broccoli – Matures in 50-70 days. Choose varieties like Waltham or Arcadia for cold tolerance.
- Cauliflower – Ready in 55-75 days. Protect heads from frost with row covers.
- Cabbage – Takes 60-80 days. Early varieties like Early Jersey Wakefield work best.
- Brussels Sprouts – Need 90-100 days. They taste best after a hard frost.
Brassicas are heavy feeders. Add compost or balanced fertilizer at planting time for best results.
Onions And Garlic For Next Year
September is also perfect for planting alliums that will overwinter.
- Garlic – Plant cloves 4-6 inches deep in late September. Harvest next July.
- Onion Sets – Plant now for green onions in 30 days, or let them overwinter for full bulbs.
- Shallots – Similar to garlic. Plant in well-drained soil with full sun.
These crops need a cold period to develop properly. Wisconsin’s winter provides that naturally.
How To Plant A Fall Garden In Wisconsin
Follow these steps to give your September garden the best chance of success.
Prepare Your Soil
Start by clearing summer crops and weeds. Add 2-3 inches of compost and work it into the top 6 inches of soil. Test pH if possible; most vegetables prefer 6.0-7.0.
If your soil is heavy clay, consider raised beds. They warm faster and drain better in fall rains.
Time Your Planting
Count backward from your average first frost date. For example, if your frost date is October 10, count back 60 days for beets. Plant by August 10 for that crop.
For September planting, focus on crops that mature in 30-50 days. This ensures harvest before hard frost.
Use Row Covers
Floating row covers add 5-10°F of frost protection. They also keep pests away. Use lightweight fabric that lets in light and water.
Secure edges with soil or rocks. Remove covers on sunny days above 70°F to prevent overheating.
Water Wisely
Fall soil dries slower than summer soil. Water deeply once a week unless rain provides moisture. Overwatering can cause rot in cool weather.
Check soil moisture by sticking your finger 2 inches deep. If it feels dry, water.
Tips For Extending Your Harvest
You can push your garden season well into November with these techniques.
Cold Frames
A cold frame is a simple box with a glass or plastic top. It traps heat during the day and protects from frost at night. You can buy one or build your own from old windows.
Place it over your September-planted vegetables. Open the lid on warm days to prevent overheating.
Mulching
Apply 3-4 inches of straw or leaves around plants. This insulates soil and keeps roots warm. Mulch also prevents soil from splashing onto leaves.
Use straw, not hay, to avoid weed seeds. Remove mulch in spring if overwintering crops.
Succession Planting
Plant small batches every two weeks. This gives you a continuous harvest rather than one big glut. For example, sow radishes on September 1, then again on September 15.
This works well for greens, radishes, and turnips. Stop planting 4-6 weeks before your first frost date.
Common Mistakes To Avoid
Even experienced gardeners make errors in fall planting. Here are pitfalls to watch for.
- Planting too late – Check maturity dates carefully. A 60-day crop planted September 1 may not finish before frost.
- Ignoring soil temperature – Seeds need soil above 50°F to germinate. Use a soil thermometer.
- Overwatering – Cool soil holds moisture longer. Water less frequently than in summer.
- Forgetting to thin – Crowded seedlings compete for nutrients. Thin according to seed packet instructions.
- Not hardening off transplants – If using nursery starts, acclimate them slowly to outdoor conditions over 3-5 days.
Avoid these and your fall garden will thrive.
Vegetables To Avoid In September
Not every vegetable works for September planting in Wisconsin. Skip these warm-season crops.
- Tomatoes – Need 70-90 days of warm weather. Too late for September.
- Peppers – Similar to tomatoes. They need heat and long days.
- Eggplant – Very frost-sensitive. Won’t produce before winter.
- Corn – Requires warm soil and full sun. Not suitable for fall.
- Cucumbers – Need 50-70 days of warmth. Plant in spring instead.
- Pumpkins – Take 90-120 days. Plant in June for fall harvest.
Stick with the cold-hardy options listed earlier for best results.
Wisconsin’s Climate Zones And Planting
Wisconsin spans USDA zones 3b in the north to 5b in the south. This affects your September planting schedule.
Northern Wisconsin (Zones 3B-4a)
First frost typically arrives in mid-September. Focus on quick crops like radishes, spinach, and arugula. Use row covers and cold frames to extend the season.
Plant garlic and shallots in late September for next year’s harvest.
Central Wisconsin (Zones 4B-5a)
First frost around late September to early October. You have time for 40-50 day crops like kale, turnips, and beets. Succession planting works well here.
Consider planting overwintering onions for an early spring harvest.
Southern Wisconsin (Zone 5B)
First frost in mid-October. This gives you the longest fall season. Plant 50-60 day crops like broccoli, cabbage, and carrots. You can also try late plantings of lettuce and Swiss chard.
Cold frames can extend harvest into December in mild years.
Frequently Asked Questions
Can I plant tomatoes in September in Wisconsin?
No, tomatoes need warm soil and long days. They won’t mature before frost. Stick with cold-hardy vegetables instead.
What is the latest I can plant vegetables in Wisconsin?
For most crops, plant by early September. For very fast crops like radishes and arugula, you can plant until mid-September in southern Wisconsin.
Do I need to fertilize fall vegetables?
Yes, but use a balanced fertilizer with lower nitrogen. Too much nitrogen encourages leafy growth that is more frost-sensitive. Apply at planting time.
Can I reuse soil from summer containers for fall planting?
Yes, but refresh it with compost or new potting mix. Old soil may be depleted of nutrients. Also check for pests or diseases before reusing.
What vegetables survive winter in Wisconsin?
Kale, Brussels sprouts, and parsnips can survive under snow cover. Garlic and shallots overwinter well. Use mulch for extra protection.
Final Thoughts On September Planting
Planting the best vegetables to plant in September in Wisconsin gives you fresh produce well into fall. Focus on cold-hardy greens, root vegetables, and brassicas. Use row covers and cold frames to extend your season.
Prepare your soil well, time your planting correctly, and avoid common mistakes. Your fall garden can be just as productive as your spring garden.
Start with a small patch if you’re new to fall gardening. Radishes and spinach are forgiving crops for beginners. As you gain confidence, add kale, beets, and broccoli to your lineup.
Wisconsin’s cool September weather is perfect for these vegetables. Take advantage of it now for a rewarding harvest before winter sets in.
Happy gardening this September in Wisconsin. Your taste buds will thank you when you enjoy fresh greens and roots from your own backyard.