When temperatures soar outside, I often hear gardeners ask if their greenhouse becomes too hot to grow anything useful. The truth is, summer presents unique opportunities for greenhouse growing that we can’t achieve any other time of year. After managing greenhouses through scorching summers, I’ve learned that with the right crop selection and cooling strategies, your greenhouse can produce abundant harvests even when outdoor temperatures hit 90°F or higher.
The key to successful summer greenhouse growing lies in understanding which plants thrive in heat and how to manage extreme temperatures effectively. While winter greenhouses protect crops from cold, summer greenhouses create controlled microclimates that allow us to grow heat-loving vegetables, exotic crops, and succession plantings that would struggle in unpredictable outdoor conditions.
Research from Oklahoma State University Extension shows that properly managed greenhouses can maintain temperatures 15-20°F cooler than outside using basic cooling techniques. This temperature control opens up possibilities for growing everything from specialty tomatoes to tropical fruits that need consistent warmth to flourish.
Summer greenhouses face distinct challenges compared to their winter counterparts. Daytime temperatures can easily exceed 100°F without proper ventilation, creating stress conditions that halt plant growth and reduce yields. I’ve measured temperatures as high as 120°F in unventilated greenhouses during July heat waves – conditions that would kill most plants within hours.
The primary difference between summer and winter greenhouse management revolves around heat dissipation rather than heat retention. While winter growing focuses on capturing and storing solar energy, summer growing requires active cooling, increased air circulation, and strategic shading to prevent overheating. Most vegetables stop photosynthesizing effectively above 86°F, making temperature control essential for productivity.
Humidity management becomes equally critical during summer months. High temperatures combined with plant transpiration can push humidity levels above 85%, creating ideal conditions for fungal diseases. Proper ventilation not only cools the greenhouse but also maintains humidity between 50-70%, the sweet spot for most summer crops.
Tomatoes remain the most popular summer greenhouse crop, and for good reason. These heat-lovers flourish in temperatures between 70-85°F, producing more fruit in controlled greenhouse conditions than in outdoor gardens. I’ve consistently harvested 15-20 pounds per plant from indeterminate varieties grown in summer greenhouses, nearly double my outdoor yields.
The best varieties for summer greenhouse production include heat-tolerant cultivars like Cherokee Purple, Brandywine, and San Marzano. These varieties maintain fruit set even when temperatures occasionally spike above 90°F. Cherry tomatoes like Sungold and Sweet 100 prove especially productive, often producing fruit continuously from June through October.
University of Minnesota Extension research demonstrates that greenhouse tomatoes grown during summer months can achieve 30% higher yields than field-grown plants due to protection from rain damage, consistent temperatures, and reduced disease pressure. The controlled environment also extends the harvest season by 6-8 weeks compared to outdoor growing.
Peppers and eggplants actually require high temperatures that summer greenhouses naturally provide. Sweet bell peppers need consistent temperatures above 70°F for proper fruit development, while hot peppers like habaneros and ghost peppers demand even higher temperatures to develop their signature heat.
I’ve found that pepper plants in summer greenhouses produce twice as many fruits as outdoor plants, with harvests starting 3-4 weeks earlier. The protected environment eliminates issues like sunscald and blossom end rot that commonly affect outdoor pepper crops during temperature fluctuations.
Asian eggplant varieties particularly excel in summer greenhouses. Japanese varieties like Ichiban and Thai Long Green tolerate heat better than traditional Italian types, producing tender fruits continuously throughout the season. The greenhouse environment protects delicate eggplant flowers from rain damage, ensuring better pollination and fruit set.
Vining cucumbers trained vertically make excellent use of greenhouse space during summer. European greenhouse varieties like Socrates and Corinto produce seedless fruits perfect for fresh eating. These parthenocarpic varieties don’t require pollination, eliminating the need for managing bees in your greenhouse.
Summer squash, particularly compact bush varieties, adapt well to container growing in greenhouses. Yellow crookneck and pattypan squashes produce prolifically in warm conditions, with the added benefit of protection from squash vine borers and cucumber beetles that plague outdoor plants.
For those interested in exploring different greenhouse setups, lean-to greenhouse designs offer excellent options for summer growing while maximizing space efficiency against existing structures.
Summer greenhouses create perfect conditions for Mediterranean herbs that demand hot, dry conditions. Basil grows explosively in summer heat, producing aromatic leaves continuously when harvested regularly. I harvest basil twice weekly during peak summer, yielding enough for fresh use, pesto making, and drying.
Oregano, thyme, and rosemary flourish in summer greenhouse conditions that mimic their native Mediterranean climate. These drought-tolerant herbs actually prefer the lower humidity levels we maintain through proper ventilation, developing more concentrated essential oils that enhance their flavor.
Summer greenhouse conditions open doors to growing exotic crops impossible in most outdoor gardens. Lemongrass, ginger, and turmeric thrive in the consistent warmth and humidity. I successfully harvest fresh ginger root after 8-10 months of growth, something unachievable in temperate outdoor climates.
Dwarf citrus trees like Meyer lemons and calamondin oranges flourish in summer greenhouses, setting fruit that ripens through fall and winter. These container-grown trees benefit from the protected environment and consistent temperatures that promote flowering and fruit development.
Okra, traditionally a deep South crop, produces abundantly in northern greenhouses during summer. The controlled environment eliminates the temperature fluctuations that slow okra production, resulting in tender pods ready for harvest every 2-3 days.
Proper ventilation forms the foundation of summer greenhouse management. Ridge vents combined with side vents create natural convection currents that pull hot air up and out while drawing cooler air in at ground level. I recommend vent openings equal to at least 20% of your floor area for adequate summer ventilation.
Automatic vent openers prove invaluable during summer, responding to temperature changes without constant monitoring. These wax-filled cylinders expand and contract with temperature, opening vents when temperatures rise above 75°F and closing them as evening temperatures drop.
For comprehensive cooling solutions and advanced techniques, explore these proven greenhouse cooling strategies that can reduce temperatures by up to 20°F during peak summer heat.
Shade cloth reduces light intensity by 30-70%, significantly lowering greenhouse temperatures. I use 40% shade cloth for tomatoes and peppers, while leafy greens benefit from 60% shading during intense summer sun. The cloth can be installed inside or outside, with external installation proving more effective at heat reduction.
Liquid shading compounds painted on greenhouse glazing offer a temporary alternative to shade cloth. These products gradually wear off through fall, eliminating the need for removal as light levels naturally decrease. One application typically lasts 3-4 months, perfectly covering the intense summer period.
Evaporative cooling can reduce greenhouse temperatures by 15-20°F in dry climates. Simple misting systems that spray fine water droplets into the air provide immediate cooling as water evaporates. I run misters for 30 seconds every 10 minutes during the hottest part of the day, maintaining temperatures below 85°F even on 100°F days.
Wet wall systems offer more sophisticated evaporative cooling for larger greenhouses. Water trickles through corrugated pads while fans pull air through, cooling and humidifying simultaneously. These systems work best in areas with less than 50% ambient humidity.
Summer greenhouse crops require significantly more water than winter plantings due to increased transpiration rates. Drip irrigation systems deliver water directly to root zones, reducing waste and maintaining consistent soil moisture. I’ve reduced water usage by 40% switching from overhead watering to drip systems.
Capillary matting provides another water-efficient option for container plants. Plants draw water as needed from saturated mats, eliminating overwatering while ensuring consistent moisture. This passive system works especially well for herb production and seedling propagation.
Collecting rainwater from greenhouse roofs provides free, chemical-free irrigation water perfect for organic growing. A 1,000 square foot greenhouse roof can harvest approximately 600 gallons from one inch of rainfall. I store collected water in food-grade barrels positioned to gravity-feed drip irrigation lines.
Installing gutters and downspouts requires minimal investment but yields significant water savings through the season. First-flush diverters remove debris and contaminants from initial runoff, ensuring clean water storage. This sustainable practice reduces reliance on municipal water while providing plants with naturally soft water they prefer.
Organic mulches like straw or shredded leaves reduce soil moisture evaporation by up to 70% in greenhouse beds. I apply 3-4 inch layers around established plants, keeping mulch away from stems to prevent rot. This practice also moderates soil temperature, keeping roots cooler during extreme heat.
Reflective mulches made from aluminum-coated plastic provide dual benefits: moisture retention and increased light reflection to lower plant leaves. These specialized mulches also repel aphids and whiteflies, common summer greenhouse pests attracted to yellow and green colors.
Companion planting maximizes greenhouse space while providing natural pest control. I interplant basil with tomatoes to repel aphids and whiteflies while improving tomato flavor. Marigolds planted along greenhouse edges deter many insects while adding colorful blooms that attract beneficial pollinators.
Vertical growing techniques allow multiple crop layers in limited space. Cucumber vines trained up strings create shade for lettuce growing below, while nitrogen-fixing beans planted with heavy-feeding tomatoes improve soil fertility naturally.
Summer greenhouse conditions can accelerate pest reproduction, making prevention crucial. Yellow sticky traps monitor and control flying pests like whiteflies and fungus gnats. I check traps weekly, replacing them when covered with insects to maintain effectiveness.
Beneficial insects provide sustainable pest control without chemicals. Ladybugs consume 50-60 aphids daily, while lacewing larvae devour spider mites, thrips, and whitefly eggs. Releasing beneficials early in the season prevents pest populations from establishing.
Neem oil applications every 10-14 days prevent most common greenhouse pests while remaining safe for beneficial insects when applied correctly. This organic treatment disrupts pest reproduction cycles without leaving harmful residues on edible crops.
Summer’s accelerated growth demands consistent nutrition. I top-dress container plants monthly with compost, providing slow-release nutrients that won’t burn roots in hot conditions. Worm casting tea applied weekly supplies immediately available nutrients while improving soil biology.
Cover crops planted between summer crop rotations rebuild soil health naturally. Buckwheat grows quickly in summer heat, adding organic matter while attracting beneficial insects. Crimson clover fixes nitrogen for fall crops while preventing soil erosion during intense summer storms.
Succession planting ensures continuous harvests throughout summer and into fall. I start new lettuce seedlings every two weeks, maintaining fresh salad greens despite summer heat. Quick-maturing crops like radishes and baby greens fill spaces between slower-growing tomatoes and peppers.
Planning successions requires understanding days to maturity in greenhouse conditions, typically 20-30% faster than outdoor growing. Bush beans planted in early June produce by late July, leaving time for fall brassica transplants in the same space.
Timing the transition from cool-season spring crops to heat-loving summer plants prevents production gaps. I start summer transplants in late April while spring crops still produce, ensuring seamless transitions as temperatures rise.
Some crops bridge both seasons successfully. Swiss chard and New Zealand spinach tolerate heat better than traditional spinach, providing greens through summer when planted in partially shaded greenhouse areas. These transitional crops maintain production while summer crops establish.
For gardeners looking to expand their growing capabilities, incorporating indoor greenhouse tips can help maintain year-round production cycles and experiment with season extension techniques.
Extreme temperatures above 90°F or below 55°F cause blossom drop in tomatoes and peppers. I maintain nighttime temperatures above 60°F and daytime temperatures below 85°F during flowering for optimal fruit set. Installing shade cloth during heat waves prevents stress-induced flower abortion.
Poor pollination in greenhouse tomatoes requires manual intervention since wind and insects are limited. Gently shaking plants daily or using an electric toothbrush on flower clusters ensures pollen transfer. Some growers install small fans to create air movement that aids natural pollination.
High temperatures increase plant metabolism, potentially causing nutrient deficiencies even in well-fertilized soil. Calcium deficiency appears as blossom end rot in tomatoes and peppers during rapid growth periods. I apply calcium foliar sprays weekly during fruit development to prevent this common problem.
Iron chlorosis, indicated by yellowing between leaf veins, occurs when high pH or excessive moisture limits iron availability. Chelated iron applications correct deficiencies quickly, restoring healthy green growth within days.
Fungal diseases proliferate in summer greenhouse humidity. Proper spacing ensures air circulation between plants, reducing disease incidence by 50%. I maintain 18-24 inches between tomato plants and prune lower leaves to improve airflow.
Watering early in the day allows foliage to dry before evening, preventing conditions that favor disease development. Drip irrigation eliminates overhead watering that spreads pathogens through water splash.
Grafting heirloom tomato varieties onto disease-resistant rootstock combines flavor with vigor. This advanced technique increases yields by 30-50% while preventing soil-borne diseases. I graft prized heirloom varieties onto hybrid rootstock, achieving disease resistance without sacrificing taste.
The grafting process requires practice but pays dividends in challenging summer conditions. Grafted plants tolerate temperature extremes better and produce longer than standard plants, extending harvests well into fall.
Hydroponic systems excel in summer greenhouses, providing precise nutrient control and eliminating soil-borne disease issues. Nutrient film technique (NFT) systems work particularly well for leafy greens and herbs, producing clean crops in 30-40% less time than soil growing.
Aquaponics combines fish farming with vegetable production, creating sustainable closed-loop systems. Tilapia thrive in warm summer water temperatures while their waste provides nutrients for vegetables. This integrated approach produces both protein and vegetables using 90% less water than traditional growing.
These advanced systems require initial investment and learning but offer superior production efficiency and sustainability. For additional inspiration on greenhouse projects and innovative growing techniques, explore these creative summer garden projects that complement greenhouse production.
Summer greenhouse growing transforms what many consider the “off season” into your most productive period. The combination of controlled environment, extended growing season, and protection from pests and weather extremes justifies the investment in cooling equipment and management time.
Cost analysis shows summer greenhouse production can reduce grocery bills by $100-200 monthly for a family of four. Premium varieties like heirloom tomatoes selling for $6-8 per pound at farmers markets cost less than $1 per pound to grow, not counting the superior flavor and freshness.
The environmental benefits extend beyond personal savings. Growing your own summer produce eliminates transportation emissions, packaging waste, and pesticide exposure. One 8×12 greenhouse can offset approximately 500 pounds of CO2 annually through local food production.
Most vegetables stop growing effectively above 86°F and experience damage above 95°F. Optimal summer greenhouse temperatures range from 75-85°F during the day and 60-70°F at night. Installing thermometers at plant level provides accurate readings for management decisions.
Yes, heat-tolerant lettuce varieties like Jericho, Nevada, and Muir grow successfully in summer greenhouses with adequate shading. Using 60% shade cloth and maintaining temperatures below 80°F prevents bolting and bitter flavors.
Summer greenhouse plants typically need daily watering, with large tomato plants requiring up to 2 gallons per day during peak production. Check soil moisture 2 inches deep – if dry, water thoroughly until drainage occurs.
Tomatoes, peppers, and eggplants benefit from manual pollination in greenhouses where natural pollinators are limited. Gently shake plants or tap flower clusters daily during morning hours when pollen is most viable.
Gravel or decomposed granite provides excellent drainage while allowing some evaporative cooling. These materials also retain less heat than concrete, helping maintain cooler root zones during summer.
Increase ventilation, space plants properly, water early in the day, and use fans to circulate air. Maintaining humidity between 50-70% prevents both disease problems and excessive plant stress.
Summer greenhouses rarely need supplemental lighting due to long daylight hours. However, shade-loving plants under heavy shade cloth might benefit from LED grow lights during cloudy periods.
Dwarf varieties of tropical fruits like bananas, papayas, and passion fruit thrive in summer greenhouse conditions. These plants require consistent warmth above 60°F and high humidity, conditions easily maintained in summer.
Summer greenhouse growing rewards gardeners with abundant harvests of heat-loving crops impossible to grow outdoors in many climates. The initial learning curve of managing heat and humidity gives way to productive systems that extend growing seasons and increase food security.
I encourage starting simple with proven crops like tomatoes and peppers before experimenting with exotic varieties. Each summer brings new lessons about variety selection, cooling strategies, and water management that improve subsequent seasons’ success.
The sustainable practices we implement in summer greenhouses – from rainwater harvesting to biological pest control – create resilient growing systems that benefit both gardeners and the environment. As climate patterns become more unpredictable, the controlled environment of a greenhouse provides insurance against weather extremes while producing nutritious food year-round.
Whether you’re growing for fresh summer salads, preserving the harvest, or selling at local markets, summer greenhouse production offers opportunities limited only by imagination and dedication to learning. The investment in proper cooling and management pays dividends through increased yields, extended seasons, and the satisfaction of growing your own food sustainably.
Don't let aphids, slugs, and caterpillars ruin another plant. Take back control with simple, natural methods that actually work.
