What To Grow In Michigan Greenhouses Each Season

Michigan has a wide range of climates, from colder Upper Peninsula zones to milder southwest Lower Peninsula zones. Greenhouses give you control over temperature, humidity, and light so you can extend the growing season or grow crops year-round. This guide explains what to grow in Michigan greenhouses in winter, spring, summer, and fall, with practical schedules, temperature targets, crop recommendations, and management tips for reliable production.

Understanding Michigan’s seasonal constraints and greenhouse types

Michigans last and first frost dates vary by region, typically from late April to mid-May for last spring frost and from late September to mid-October for first fall frost in much of the Lower Peninsula. The Upper Peninsula and northern areas are colder. That matters for how long you need heat and what crops you can move outdoors.
Common greenhouse types used in Michigan:

• Cold frames and unheated hoop houses – good for early spring and late fall cold-tolerant crops.
• Single-layer polyethylene hoop houses – economical, moderate insulation.
• Double-poly or twin-wall poly greenhouses – much better for winter and energy efficiency.
• Glass or polycarbonate heated greenhouses with supplemental lighting – for year-round production.

When I recommend crops below I assume you know the greenhouse type and whether you will provide supplemental heat and light. Unheated structures are limited to cool-season crops and season extension. Heated, insulated greenhouses allow full-year production.

Year-round greenhouse essentials (temperature, light, water, and substrate)

Before picking crops, dial in these fundamentals:

• Temperature: Use target ranges by crop group. Cool-season greens: 45-65 F night, 55-70 F day. Warm-season vegetables (tomato, pepper, cucumber): 60-70 F night, 70-80 F day. Seed germination often needs higher bottom heat: 70-85 F depending on seed.
• Light: Michigan winter daylight is low. For consistent growth in winter use supplemental LED or high-output lights. Lettuce and herbs can get by with 12-14 hours; fruiting crops need 14-16 hours and higher light intensity.
• Humidity and ventilation: Maintain 50-70 percent relative humidity depending on crop. Warm, humid conditions increase fungal risk; use vents, fans, and horizontal airflow to reduce disease.
• Water and fertilizer: Use well-draining soilless mixes for containers and benches. Monitor EC and pH: most vegetables prefer pH 5.8-6.5. Fertilize regularly with balanced fertilizer; increase potassium for fruit development.
• Pollination: For enclosed greenhouses, hand pollinate tomatoes and peppers with a brush or use bumblebee hives for larger operations. Cucumbers and squash may need pollinator access or parthenocarpic varieties.

Winter: maximize production in cold months

Winter is the time for controlled-environment production. With heating and lights you can grow high-value crops and seedlings for spring sales.
What to grow in winter:

• Microgreens and baby salad mixes (arugula, mustard, kale, cress): fast turnaround (7-21 days), high-value, low light requirements.
• Cut-and-come-again lettuces and spinach: choose loose-leaf and winter-hardy varieties; grow under supplemental light at cooler temperatures (50-60 F) for crisp texture.
• Herbs: parsley, cilantro, chives, thyme, and rosemary (slow growth but steady yield). Basil struggles in cool winter without supplemental light and heat.
• Leafy Asian greens: tatsoi, mizuna, bok choy for quick harvests.
• Seedlings: start tomato, pepper, eggplant, and transplant-ready brassicas for spring sale or transplanting.
• Cut flowers: spray chrysanthemums, pansies, violas, and anemones in heated houses for niche markets.

Management tips for winter:

1. Use double poly and thermal curtains to reduce heating loads.
2. Provide 12-16 hours of light for baby greens and 14-16 hours for tomato seedlings.
3. Keep night temps cooler for leafy crops (50-60 F) to avoid leggy growth and to improve quality.
4. Use bottom heat mats for seed germination and plug production to speed emergence.
5. Monitor and control Botrytis and powdery mildew by keeping humidity moderate and providing air movement.

Practical takeaways: Winter production favors quick-turn, high-value crops that tolerate low light and cooler temps. Microgreens and salad mixes give fast cashflow; use seedlings to head-start the spring season.

Spring: transition and succession

Spring is a busy time: hardening off, staging transplants, and planting early crops. Use the greenhouse for both protected production and to generate plants for field transplanting.
What to grow in spring:

• Early cool-season crops: peas (sugar snap), radishes, early carrots (in deep containers), beets, and kale.
• Transplants: tomatoes, peppers, eggplant, brassicas (broccoli, cabbage), and warm-season herbs started 6-8 weeks before last frost for tomatoes and peppers, 3-4 weeks earlier for brassicas.
• Cold-tolerant salad greens and spinach for elevated production before outdoor beds warm up.
• Overwintered crops: if you carried some kale or spinach through winter, you can cut back and get early spring harvests.

Timing guidelines:

• Start tomatoes and peppers 6-8 weeks before your expected last frost date.
• Start basil and cucumbers 3-4 weeks before transplant.
• Direct-seed peas and radishes in greenhouse soil beds as soon as you can maintain soil temps above 40 F.

Management tips for spring:

• Gradually harden seedlings to outdoor conditions by increasing ventilation and lowering night temps over 7-10 days before planting outside.
• Stage transplant sizes so you can send batches out as weather allows.
• Use succession plantings for greens every 10-14 days to maintain a steady supply.

Practical takeaways: The greenhouse is a propagation and early-production engine in spring. Focus on producing healthy, hardened transplants and early harvests of cool-season crops.

Summer: heat-loving crops and managing heat stress

Summer can be the highest-yield greenhouse season, but heat and humidity become the main challenges.
What to grow in summer:

• Tomatoes (indeterminate and determinate varieties), peppers, cucumbers, eggplant, melons if space and pollination are provided.
• Basil, oregano, and other Mediterranean herbs that thrive in warm conditions.
• Summer greens planted in cooler spots or shade cloth: Swiss chard, amaranth, and heat-tolerant lettuce varieties.

Temperature and light management:

• Target daytime temps of 70-85 F for fruiting crops; allow nights to be 60-70 F.
• Use shade cloth (30-50 percent) during the hottest weeks to prevent sunscald and overheating.
• Ventilation and evaporative cooling are essential; maintain airflow and use roll-up sides or exhaust fans.

Water and fertility:

• Increase irrigation frequency but maintain good drainage. Drip irrigation and fertigators are best for consistent moisture and feeding.
• High potassium during fruit set supports yield; avoid excessive nitrogen that promotes vegetative growth at the expense of fruit.

Pest management:

• Spider mites, whiteflies, aphids, and thrips increase in hot, dry conditions. Monitor weekly and use biological controls and targeted treatments as needed.

Practical takeaways: Summer is when greenhouses can produce their highest yields. Focus on cooling, ventilation, and integrated pest management to protect fruiting crops.

Fall: second crops and overwintering strategies

Fall offers another window for cool-season production and a chance to overwinter hardy crops.
What to grow in fall:

• Second plantings of salad greens, spinach, kale, and mustard for fall harvests.
• Overwintering crops: garlic (planted in fall for harvest next summer) and cold-hardy brassicas that can be protected with row cover or low heat.
• Bulb onions and leeks for prolonged harvests.
• Fall flowering crops such as mums and pansies for retail sales.

Season extension techniques:

• Use low tunnels or row cover inside the greenhouse for extra cold protection without heavy heating.
• Plant 6-8 weeks earlier than outdoor dates to ensure maturity before light drops too far in late fall.
• For overwintering leafy crops, maintain temps just above freezing (32-40 F) in cold frames or minimally heated spaces.

Pest and disease considerations:

• Clean up crop residues promptly to reduce overwintering pests and diseases.
• Inspect irrigation lines and benches for mold growth and sanitize before winter storage.

Practical takeaways: Use fall to squeeze in a second round of cool-season vegetables and to prepare overwintering plantings. Proper sanitation and staged planting extend harvest windows.

Varieties and cultivar selection for Michigan greenhouses

Choosing the right variety makes or breaks greenhouse success. Prioritize disease resistance, compact growth for bench space, and varieties bred for greenhouse production when available.
Recommended choices:

• Lettuce: ‘Winter Density’, ‘Nevada’, ‘Salinas’ series for greenhouse; choose loose-leaf types for repeated harvesting.
• Tomatoes: indeterminate greenhouse hybrids with good fruit set at lower light, e.g., disease-resistant high-yield hybrids. Look for varieties with resistance to powdery mildew and root diseases.
• Cucumbers: parthenocarpic greenhouse varieties require no pollination and set fruit in enclosed structures.
• Peppers: blocky and long types with powdery mildew and bacterial spot resistance.
• Herbs: ‘Gigante d’Italia’ basil for summer, ‘Curly Parsley’ for year-round, and ‘Lemon Thyme’ for winter growth.

Practical takeaways: Invest in greenhouse-specific cultivars and prioritize disease resistance and compact habits to maximize space.

Pest, disease, and sanitation protocols

Consistent sanitation and monitoring reduce losses and improve yield.
Key practices:

• Remove crop residue and sanitize benches and tools after each crop cycle.
• Implement weekly scouting for pests and diseases; use sticky traps and visual inspection.
• Quarantine new plant material for a week and inspect for pests.
• Use biological control agents where practical (predatory mites, parasitoid wasps).
• Rotate crop families in the greenhouse beds or containers to reduce soilborne disease build-up.

Practical takeaways: Prevention is far more effective than cure. A sanitation plan and regular scouting are foundational.

Scheduling and succession planting for year-round production

To keep production steady and minimize empty bench space, manage succession planting deliberately.
Guidelines:

1. Map a 12-month calendar of crops, noting key planting and harvest windows for each zone of your greenhouse.
2. Stagger plantings of greens every 7-14 days for continuous harvests.
3. Time seed starting for warm-season crops 6-8 weeks before transplant and for cool-season crops 2-4 weeks prior depending on desired harvest size.
4. Balance fast-turn crops (microgreens, radishes) with longer crops (tomatoes) so you always have revenue-producing space.

Practical takeaways: A simple planting calendar and staggered seeding will turn your greenhouse into a steady production system rather than a boom-and-bust cycle.

Final checklist before planting each season

• Verify heating and thermostat settings for seasonal needs.
• Inspect glazing, seals, and vents for drafts or damage.
• Clean benches, trays, and tools and disinfect where necessary.
• Test soil or substrate pH and EC and adjust before planting.
• Stock appropriate fertilizers, biologicals, and pest control supplies.
• Prepare a planting and harvest schedule tied to your local last and first frost dates.

Growing in Michigan greenhouses gives you flexibility to produce high-quality crops through every season if you match crop selection to your structure, control environment variables carefully, and plan plantings for continuous production. Prioritize insulation and light in winter, ventilation and cooling in summer, and sanitation year-round. With the right varieties and schedules you can supply fresh greens, herbs, seedlings, and fruiting crops to markets and tables throughout the year.