Growing strawberries in a controlled environment allows for year-round production, extended harvest seasons, and higher yields, ensuring consistent fruit availability. The greenhouse structure provides a protective barrier against extreme weather and many outdoor pests, significantly benefiting crop health. By manipulating the internal climate and nutrient delivery, growers can ensure the strawberry plants receive optimal conditions for every stage of development. This controlled approach leads to the cultivation of high-quality, flavorful berries regardless of the external climate.
Setting Up the Greenhouse Structure
Selecting the appropriate strawberry variety is the first step in establishing a successful greenhouse operation. Day-neutral cultivars, such as ‘Albion,’ ‘San Andreas,’ or ‘Seascape,’ are highly favored because they produce flowers and fruit continuously, independent of day length, provided temperatures remain suitable. Traditional June-bearing varieties, which produce a single large crop, are less common for commercial greenhouse growing aimed at continuous production.
Modern greenhouse cultivation relies on soilless systems, which offer better control over water and nutrient delivery and mitigate soil-borne diseases. Common growing media include coco coir, known for its excellent air-filled porosity, or specialized mixes of peat, wood fiber, and perlite. These media are typically housed in containers, specialized grow bags, or vertical tiered systems like hanging or ground-mounted gutters.
Vertical setups maximize the number of plants per square foot, significantly boosting overall yield within the greenhouse footprint. Proper installation of benches or gutters must account for drainage, ensuring excess water from precision irrigation systems is efficiently routed away. The greenhouse structure should be oriented to maximize natural light exposure, although supplemental systems are necessary for year-round production.
Mastering Climate Control
The ability to precisely manage the internal environment is the primary advantage of greenhouse cultivation, starting with temperature control. During the vegetative stage, plants thrive with warmer daytime temperatures, ideally 18–24°C (64–75°F), paired with cooler nights of 10–13°C (50–55°F). As the plants enter flowering, the daytime temperature should be slightly reduced to 16–20°C (60–68°F) to support proper flower formation and pollen viability.
Once fruit set begins, the temperature should be maintained around 15–20°C (59–68°F) during the day and kept cool at night, ideally 8–12°C (46–54°F), which promotes sugar accumulation and improves berry flavor. Managing humidity is equally important, as strawberries are highly susceptible to fungal diseases like Botrytis (gray mold) in moist conditions. The optimal relative humidity (RH) range is 60–75%, and it should not exceed 85% at night.
Air movement, facilitated by circulation fans, is essential for continuous ventilation, regulating humidity and preventing microclimates where diseases can flourish. Moving air also ensures that carbon dioxide (CO2) is evenly distributed around the leaf canopy, maximizing photosynthetic efficiency. Supplemental lighting is required, particularly during winter months, to ensure a Daily Light Integral (DLI) of 15 to 25 mol/m²/day is met for high fruit production.
Essential Care and Pollination Strategies
Nutrient delivery in soilless systems is achieved through fertigation, where water and a precise nutrient solution are supplied directly to the root zone via drip lines. The required nutrient concentration changes significantly as the plant moves from vegetative growth to fruiting. During the flowering and fruiting stages, the focus shifts to phosphorus and potassium to encourage fruit development and quality.
A common nutrient formulation for fruiting strawberries includes a low nitrogen (N) concentration, around 160–170 parts per million (ppm), combined with high potassium (K), in the range of 400–500 ppm, to enhance sweetness and color. This high potassium ratio is important because potassium plays a direct role in sugar transport within the plant. Calcium and magnesium are also monitored, as calcium helps prevent blossom-end rot and maintain fruit firmness.
Pollination is one of the most significant challenges in a closed greenhouse environment, as natural wind and insect activity are absent. For commercial scale, introducing colonies of bumblebees or honeybees is the most effective method, resulting in larger, better-formed fruit and a higher overall yield. For smaller operations, manual pollination is a viable alternative, involving gently brushing the center of an open flower with a soft brush or cotton swab to transfer pollen.
Plant management includes the removal of runners, which are horizontal stems produced for asexual reproduction. Allowing runners to grow diverts the plant’s energy away from fruit production, so they should be snipped off to concentrate resources on berry development. Pruning the first few flower buds on new plants is also a recommended practice, as this encourages the plant to establish a stronger root system, leading to higher yields later in the season.
Managing Closed-System Pests and Diseases
The enclosed nature of a greenhouse creates a stable environment where certain pests can thrive and multiply rapidly without natural predators. Common threats include the two-spotted spider mite, which flourishes in warm, dry conditions, along with aphids, thrips, and whiteflies. These pests damage plants by sucking out plant juices and can quickly compromise the crop if left unchecked.
Integrated Pest Management (IPM) is the preferred strategy in a closed system, emphasizing proactive monitoring and biological controls over broad-spectrum chemical use. This includes placing yellow sticky traps throughout the greenhouse to monitor pest populations and establishing physical barriers. The most effective method involves releasing beneficial insects, such as predatory mites like Phytoseiulus persimilis or Neoseiulus californicus, which actively hunt and consume spider mites.
Disease prevention is primarily a function of climate control, as high humidity and poor air circulation are the main catalysts for fungal infections. Gray mold (Botrytis cinerea) can devastate fruit, but it is largely prevented by maintaining the optimal relative humidity and ensuring consistent ventilation. Prompt removal of any infected plant material and maintaining high sanitation standards within the facility are important steps in preventing rapid disease spread.