What To Plant For Fall Harvests In Louisiana Greenhouses

Growing fall crops in a Louisiana greenhouse is one of the best ways to extend production through the sticky summer and into the cooler months. With hot, humid summers and mild winters, Louisiana presents both advantages and challenges for a fall harvest. This guide covers what to plant, when to plant, and how to manage a greenhouse to get reliable, high-quality fall yields in Louisiana’s climate zones.

Climate and timing basics for Louisiana greenhouses

Louisiana falls into USDA zones roughly between 8a and 10a depending on location. Fall in Louisiana can be a long, gradual transition from summer heat to mild winter temperatures. In a greenhouse you must plan for three distinct periods:

• Late summer heat (August to early September) when greenhouse temperatures can spike above 100 degrees F without shading and ventilation.
• Transitional fall (mid-September to November) when nights cool to the 50s-60s F and days are mild.
• Late fall/early winter (December to January) when nights can drop into the 30s-40s F in northern parishes and remain mild near the coast.

For fall harvests you will usually start seeds or transplants in mid to late summer so crops mature from September through December, depending on crop and target harvest window.

Best crops to plant for fall harvests

Selecting crops that thrive in cool to mild conditions and that tolerate Louisiana humidity is key. Below are categories and recommended varieties to prioritize for fall greenhouse production.

Leafy greens and salad crops

Leafy crops are the fastest path to fall harvests and are well-suited to greenhouse production.

• Lettuce: Choose looseleaf varieties such as ‘Black Seeded Simpson’, ‘Salvius’, or heat-tolerant mixes for early fall plantings. Plant every 10 to 14 days for continuous harvest.
• Spinach: Plant baby leaf spinach in late summer for fall harvest; varieties bred for heat tolerance reduce bolting.
• Arugula, mizuna, tatsoi: Fast-maturing Asian greens that tolerate low light and provide multiple harvests.
• Swiss chard and mustard greens: Good for midsized harvests and heat-tolerant enough for late summer starts.

Brassicas (cabbage family)

Brassicas prefer cooler conditions and are excellent for fall harvests started in mid to late summer.

• Broccoli: Transplant seedlings in August for a fall harvest; varieties like ‘Green Magic’ or ‘Packman’ are reliable.
• Cauliflower: More temperature sensitive but possible if nights cool gradually; use varieties with some heat tolerance.
• Cabbage: Varieties such as ‘Savoy’ and ‘Red Acre’ perform well for fall head formation.
• Collards and kale: Very reliable in Louisiana fall, tolerate heat and cold; harvest continuously.

Root crops

Roots are simple to grow in containers or beds and store well after harvest.

• Radishes: Among the fastest crops, maturity in 25 to 35 days depending on variety.
• Beets: Both roots and greens harvestable; plant in late summer for fall roots.
• Carrots: Plant early enough for roots to size before hard freezes; use deep containers or raised beds with loose soil.
• Turnips and rutabagas: Good for fall planting and can be stored.

Legumes and vines

Some warm-season crops can be timed for fall production by starting them in mid-summer.

• Snow peas and snap peas: Plant in late summer for fall pods; give trellis support and partial shade if day temps remain high.
• Cucumbers and summer squash: If you want fall harvests, start hybrids in mid to late summer and control greenhouse heat in August.

Herbs

Herbs can make excellent fall greenhouse crops, especially those that appreciate cool nights.

• Cilantro: Bolts quickly in heat; start in late summer for fall harvest.
• Parsley: Slow to establish but productive through fall and winter.
• Dill and chives: Good for cut-and-come-again harvests.
• Basil: Plant earlier for late summer and early fall harvest, but be ready to protect from cold nights.

Fruit crops to consider

Tomatoes and peppers can be timed for fall production, especially in a greenhouse where temperatures can be moderated.

• Determinate tomato varieties: Easier to manage and harvest in a defined period; start transplants mid-summer for fall ripening.
• Peppers: Start transplants in late spring or early summer for fruit that matures into the fall.

When to seed and transplant: a practical schedule

Use this simplified schedule as a starting point. Adjust by local microclimate and greenhouse conditions.

• Late June to mid July: Start transplants of tomatoes, peppers, and cucurbits if targeting a late fall fruit harvest. Prepare brassica seedlings.
• Mid July to early August: Seed fast-maturing greens like arugula and radish for a late summer/early fall harvest. Begin lettuce succession plantings.
• Mid August to early September: Transplant broccoli, cabbage, kale, and collards. Direct sow beets, carrots, and turnips in well-prepared beds.
• September to October: Continue succession sowings of lettuce, spinach, and baby greens every 10-14 days. Plant peas and fall cucurbits early in this window for mild late fall harvesting.

Greenhouse environmental management

Louisiana’s heat and humidity require active greenhouse management for fall success.

Ventilation and cooling

• Use roof vents, side vents, and circulating fans to avoid heat spikes in late summer. Passive ventilation is seldom enough in August.
• Consider evaporative cooling pads or shade cloth (30 to 50 percent shading) during the hottest months to prevent heat stress on young transplants.

Humidity control

• High humidity favors fungal diseases. Provide good airflow between plants, use drip irrigation instead of overhead watering when possible, and reduce night-time humidity by running vents before dusk.

Heating for late fall

• Minimal heating is usually sufficient in southern Louisiana, but in northern parishes a small heater or row covers may be necessary when nights dip near freezing. Insulate the structure and use thermal curtains for overnight protection.

Light and daylength

• Most fall crops tolerate shorter days, but young transplants benefit from high light. Use reflective floor treatments or supplemental lighting only if harvest schedules require faster growth.

Soil, containers, and fertility

Healthy media and sensible fertility make greenhouse fall crops productive.

• Soil mix: Use a well-draining mix with compost and coarse sand for beds; container mixes should be light, sterile, and high in organic matter.
• pH: Aim for 6.0 to 6.8 for most vegetables. Brassicas tolerate slightly higher pH.
• Fertility: Apply a balanced fertilizer at planting. Leafy greens respond to additional nitrogen; side-dress with compost tea or a soluble nitrogen source every 3 to 4 weeks for heavy feeders.
• Organic amendments: Well-composted manure or compost improves structure and micronutrients. Avoid fresh manures that can burn or introduce pathogens.

Pest and disease management

Greenhouses concentrate both crop growth and pest pressure. Proactive management reduces losses.

• Scout weekly for aphids, whiteflies, thrips, and spider mites. Use yellow sticky cards and beneficial insects like lacewings and predatory mites when practical.
• Sanitation: Remove crop debris promptly; disinfect tools and bench surfaces between plantings.
• Disease prevention: Space plants for airflow, avoid overhead watering, and rotate crop families to reduce soil-borne disease buildup.
• Fungicide options: For severe fungal problems, use approved greenhouse fungicides or biological controls per label instructions. Integrated pest management (IPM) is preferred.

Spacing and planting density

Spacing depends on crop maturity and harvest style (single harvest vs cut-and-come-again).

• Lettuce (looseleaf): 6 to 8 inches between plants for baby leaves; 10 to 12 inches for full heads.
• Kale and collards: 12 to 18 inches between plants.
• Broccoli and cabbage: 18 to 24 inches between plants.
• Carrots and beets: Thin to 2 to 4 inches between roots depending on variety.
• Bush beans and peas: 3 to 6 inches between plants with trellis support for peas.

High-density plantings can increase yield per square foot for baby leaf greens but require more frequent watering and thinning.

Harvesting and post-harvest handling

Timely harvest preserves quality and shelf life.

• Harvest greens in the morning when turgor is highest. Use a sharp knife or scissors to avoid tearing leaves.
• Store harvested greens at 32 to 36 degrees F and 90 to 95 percent relative humidity for best shelf life. For Louisiana growers without cold rooms, use coolers or harvest on cooler days and bring product to market quickly.
• Root crops store well if tops are removed and roots are kept cool and moist.

Troubleshooting common fall greenhouse problems

• Bolting: Rapid temperature swings and heat stress cause bolting in lettuce and cilantro. Use shade cloth and avoid late-summer planting of bolt-prone crops unless varieties are heat-tolerant.
• Fungal leaf spots and damping off: Overcrowding and wet leaves encourage these. Improve airflow, reduce overhead irrigation, and treat soil with biological fungicides if needed.
• Poor head formation in brassicas: Warm nights during head initiation can prevent proper formation. Time transplants so the plants reach the head-initiating stage as nights cool.

Practical takeaways and quick checklist

• Prioritize fast-maturing leafy greens, collards, kale, brassicas, beets, and radishes for reliable fall greenhouse harvests.
• Start brassica transplants in July to August and seed succession plantings of greens every 10 to 14 days.
• Control late-summer heat with ventilation, fans, shade cloth, and evaporative cooling to protect transplants.
• Use drip irrigation, keep good airflow, and scout regularly for pests and disease.
• Maintain soil pH between 6.0 and 6.8, and side-dress nitrogen for leafy crops.
• Stagger plantings and use high-density beds for baby leaf production; thin and space roots carefully for storage crops.

Managing a Louisiana greenhouse for fall harvests requires planning around late-summer heat, humidity, and the gradual cooling that follows. By selecting appropriate crops, timing plantings, and actively managing the greenhouse environment, you can produce a steady succession of high-quality vegetables and herbs from late summer through early winter. Use this guide as a practical starting plan and adapt varieties and schedules to your specific parish climate and greenhouse setup.