Year-Round Strawberry Cultivation in Greenhouses: The Complete Guide!

By the AtmoSerre team

🍓 Introduction

Imagine picking juicy and fragrant strawberries in the middle of January, or extending your season until November without worrying about frost or bad weather. This dream is now accessible to all gardeners thanks to greenhouse strawberry cultivation. Whether you are a beginner or an experienced gardener, a polycarbonate greenhouse offers ideal conditions for producing strawberries all year round, in quantity and quality.

Strawberries are one of the most popular fruits in France. According to FranceAgriMer figures, the French consume an average of 2.5 kg of strawberries per person per year. However, the natural strawberry season only lasts a few weeks between April and June. With a greenhouse, you multiply your harvest period by 4 to 6, while enjoying much tastier fruits than those bought in supermarkets.

In this comprehensive guide, we will explain step by step how to grow strawberries in a greenhouse all year round: variety selection, soil preparation, planting, maintenance, temperature management, and disease prevention. Everything you need to successfully grow your strawberries under cover!

🌟 Why Grow Strawberries in a Greenhouse?

Growing strawberries outdoors is subject to the vagaries of the weather: late frosts that burn flowers, rains that promote fungal diseases, heatwaves that shrivel fruits. A polycarbonate garden greenhouse radically changes the situation.

✅ Advantages of the greenhouse for strawberry plants

🌡️ Temperature Control In a greenhouse, you maintain an optimal temperature between 15°C and 25°C, which is ideal for strawberry plant flowering and fruiting. As soon as outside temperatures drop, your greenhouse retains the heat accumulated during the day, allowing continuous growth even in winter.

💧 Protection against bad weather Direct rain on fruits promotes diseases like botrytis (grey mold). In a greenhouse, your strawberries stay dry, which significantly reduces the risk of fungal diseases and improves fruit quality.

🐛 Pest Reduction Birds, slugs, and snails that devastate your outdoor strawberries no longer have access to your greenhouse crops. This reduces your losses and the need for chemical treatments.

📅 Season Extension With a greenhouse, you can start planting your strawberry plants as early as February (compared to April outdoors) and harvest until November or even December for everbearing varieties. Some experienced gardeners harvest strawberries 10 months out of 12!

🍓 Superior taste quality Strawberries grown in a greenhouse, protected from climatic hazards, develop a higher sugar content and more intense aromas than those grown outdoors. Your strawberries will be incomparably better than store-bought ones.

To enjoy all these benefits, you first need the right greenhouse. Discover our selection of polycarbonate garden greenhouses, designed to create optimal growing conditions all year round.

🌱 Best Strawberry Varieties for the Greenhouse

Choosing the right variety is crucial for successful strawberry cultivation in a greenhouse. Not all varieties behave the same way under cover. Here are the best options depending on your goals.

🍓 Non-everbearing varieties (one harvest per year)

Ciflorette One of the most popular varieties among French gardeners. Ciflorette produces elongated, very fragrant and sweet fruits. It adapts perfectly to greenhouse cultivation, with abundant production between March and June under cover. Its firm flesh makes it ideal for freezing and jam.

Gariguette The star of French markets! Gariguette is an early variety which, in a greenhouse, can be advanced by 4 to 6 weeks compared to outdoors. Its long, slightly acidic and very fragrant fruits make it the favourite of gourmets. It grows easily in pots or directly in the ground under greenhouse conditions.

Charlotte A very productive variety with bright red, sweet and firm fruits. Charlotte is particularly disease-resistant, making it an excellent choice for beginners growing in a greenhouse.

🍓 Everbearing varieties (multiple harvests per year)

This category offers the best options for growing strawberries all year round in a greenhouse.

Mara des Bois The queen of everbearing varieties! Mara des Bois produces small, very fragrant fruits, similar to wild strawberries, from June until the first frosts (and well beyond in a greenhouse!). In a heated greenhouse, it can produce almost all year round. Its incomparable flavour makes it a favourite of artisanal strawberry lovers.

Elan A very productive everbearing variety, particularly suitable for soilless and greenhouse cultivation. Elan produces large, regular, firm and sweet fruits, from May to November outdoors, and almost all year round in a greenhouse.

Albion An American variety with enormous fruits (up to 30g per fruit!), very sweet and firm. Albion is particularly suitable for cultivation in pots or soilless culture, making it an excellent choice for the greenhouse.

Framberry An interesting new variety: a hybrid between strawberry and raspberry, very everbearing and not very demanding in terms of heat. It produces fruits with very original raspberry notes, perfect for surprising your guests.

📊 Variety comparison table

🏡 Preparing Your Greenhouse for Strawberry Cultivation

Before planting your first strawberry plants, it is essential to prepare your greenhouse properly to create an optimal environment.

📐 Choosing the right location in the greenhouse

Strawberry plants need a minimum of 6 hours of sunlight per day to produce abundantly. Orient your greenhouse preferably north-south to maximize sun exposure, and place your strawberry plants in the brightest area.

If your greenhouse has multiple zones, reserve the most sun-exposed part for strawberry plants, and the shadier areas for crops that prefer less direct light (lettuce, spinach).

🪴 Growing supports suitable for strawberries

Strawberries can be grown in several ways in a greenhouse:

In the ground or in ground-level containers The traditional method. Prepare rich, well-drained organic matter soil with a pH between 5.5 and 6.5. Add well-decomposed compost and a little sand to improve drainage.

In raised garden beds Wooden or galvanized steel raised garden beds available from AtmoSerre are particularly suitable for strawberry plants. They allow better control of the substrate, facilitate maintenance (no need to bend over!), and improve drainage. A 30 cm deep bed is sufficient for strawberry plants.

In soilless culture / in gutters The most productive technique for the greenhouse! In hydroponic culture or inclined gutters, strawberry plants produce cleaner fruits (no contact with the soil), less prone to disease, and easier to harvest. The fruits hang elegantly along the gutters. An automatic irrigation system greatly simplifies maintenance.

On shelves To maximize the vertical space in your greenhouse, use greenhouse shelves on which you place individual pots. This technique allows you to triple your growing area without increasing your footprint!

🌡️ Regulating temperature and ventilation

Strawberry plants prefer temperatures between 15°C and 25°C during the day, and between 8°C and 12°C at night. Below 5°C, growth stops. Above 30°C, flowers abort and production drops.

In summer, ventilation is crucial: install an automatic door and window opening system that opens automatically when the temperature exceeds a defined threshold. In winter, a small auxiliary heater can keep the greenhouse frost-free.

🌱 Sowing and Planting Strawberries in a Greenhouse

🗓️ When to plant strawberries in a greenhouse?

One of the great advantages of a greenhouse is being able to plant much earlier than outdoors:

• January-February: planting non-everbearing varieties for a harvest from March-April
• March-April: planting everbearing varieties for continuous production until December
• August-September: planting new plants for winter production

🌿 Starting from plants or seeds?

Plants (potted or bare-root strawberry plants) This is the recommended method for beginners. You buy already developed plants and plant them directly in the greenhouse. Harvesting is possible in the first year, often within a few weeks.

Seeds Growing from seeds takes longer (6 to 8 weeks before transplanting) but is less expensive and allows access to rare varieties. Sow in pots at 20°C under glass or in a mini-greenhouse, and transplant when the plants have 3-4 true leaves.

Runners (stolons) If you already have strawberry plants, collect the runners (long stems that the plant naturally produces) at the end of the season. Let them root in a small pot, then separate them from the mother plant once well rooted. It's free and very effective!

🌱 Planting technique

1. Prepare your substrate: mix universal potting soil, compost, and a little sand (60/30/10)
2. Plant the strawberry plants staggered, spaced 25 to 30 cm in all directions
3. The crown (junction between roots and leaves) must be at soil level, neither buried nor raised
4. Water abundantly at planting
5. Mulch with straw or wood chips to retain moisture and prevent soil splashes on the fruits

💧 Maintenance, Watering, and Fertilization

💧 Watering strawberries in a greenhouse

Strawberry plants need regular watering but without excess. Excessive water promotes root diseases and fruit rot. The golden rule: the substrate must be moist but never waterlogged.

Frequency: in summer, water every 1 to 2 days. In winter, once a week is often enough.

Method: always water at the base of the plant, never on the leaves or fruits. Overhead watering promotes fungal diseases and damages the fruits.

Automatic irrigation: To simplify maintenance, especially if you are away, a drip irrigation system is ideal. It delivers water directly to the base of the plants, at the frequency you program. Our greenhouse irrigation system is perfectly suited for this type of cultivation.

🌿 Fertilization

Strawberry plants are heavy feeders and require regular nutrient supplements:

Before planting: incorporate well-decomposed compost (3 to 5 kg per m²) into the substrate.

During vegetative growth: apply a nitrogen-rich (N) fertilizer every 2 weeks to promote leaf and runner development.

During flowering and fruiting: switch to a fertilizer rich in potassium (K) and phosphorus (P) to promote flower formation and fruit quality. Potassium, in particular, improves sugar content and aroma.

For organic growing: use crushed horn meal, nettle manure, or composted poultry droppings.

✂️ Pruning and regular maintenance

• Remove runners regularly (unless you want to propagate your plants) to concentrate the plant's energy on fruit production.
• Remove dead or diseased leaves as they appear to prevent the spread of diseases.
• Remove flowers for the first 6 weeks after planting to allow the plant to establish itself before fruiting (for new plantings only).

📅 Managing Seasons in a Greenhouse: The Complete Calendar

❄️ Winter (December - February)

This is the most delicate period for growing strawberries in a greenhouse. Here's how to manage this season:

• Maintain the temperature above a minimum of 5°C (supplemental heating if necessary)
• Drastically reduce watering (maximum once a week)
• Remove old leaves and clean the greenhouse
• Plant new early varieties from January for an early harvest
• Take advantage of this period to enrich the substrate with compost

🌸 Spring (March - May)

The most productive season for non-everbearing varieties:

• Resume regular watering as soon as vegetation restarts
• Begin potassium fertilizer applications to promote flowering
• Ventilate the greenhouse during hot days to prevent overheating
• Manually pollinate flowers if necessary (the greenhouse prevents access for pollinating insects): gently brush each flower
• Monitor for the first signs of disease (especially botrytis)

💡 Manual pollination is crucial in a greenhouse! Without bees, your strawberries may produce misshapen fruits or in small quantities. Go through the rows every morning with a soft brush or toothbrush to transfer pollen from flower to flower. Some gardeners simply open their greenhouse windows during flowering to allow insects in.

☀️ Summer (June - August)

The most problematic period in a greenhouse due to heat:

• Install a shade cloth to protect your plants from sunburn
• Open doors and windows wide in the morning for ventilation
• Water morning and evening in hot weather
• Harvest fruits as soon as they are bright red (they soften quickly in high heat)
• This is the time to prepare new plants from runners for autumn

🍂 Autumn (September - November)

The second major production period for everbearing varieties:

• Replant new plants for winter
• Gradually reduce watering as temperatures drop
• Keep the greenhouse closed at night as soon as temperatures fall below 10°C
• Harvest abundantly until the first real frosts
• Clean and disinfect the greenhouse at the end of the season

🐛 Pests and Diseases to Watch Out For

🦠 Fungal diseases

Botrytis (gray mold) The main enemy of strawberries in a greenhouse. It manifests as cottony gray spots on fruits and leaves. It is favored by stagnant humidity and lack of ventilation. Prevention: good ventilation, watering at the base, sufficient spacing between plants, removal of diseased fruits and leaves.

Powdery mildew Recognized by a white, powdery growth on the leaves. It develops in hot, dry weather with cool nights. Treatment: spray diluted baking soda (1 tablespoon per liter of water) or wettable sulfur for organic growing.

Verticillium wilt A soil fungus that causes wilting and yellowing of leaves. There is no curative treatment: practice crop rotation and use resistant varieties.

🐛 Common pests

Aphids They quickly colonize young shoots and weaken plants. In a greenhouse, without natural predators, they proliferate rapidly. Treatment: spray diluted black soap, release ladybugs (predatory insects), or use repellent plants like basil or lavender nearby.

Mites (spider mites) Very common in greenhouses in hot, dry weather. They cause yellowing and a bronze appearance of the leaves. Prevention: maintain good humidity (mites hate humidity), spray cold water under the leaves.

Thrips Tiny insects that cause deformities in leaves and fruits. Treatment: yellow sticky traps, neem oil as a preventive treatment.

To learn more about pest control in greenhouses, consult our complete article: "How to protect your plants from diseases in a greenhouse."

💡 Tips for Maximizing Your Harvests

🌡️ Tip 1: Early forcing

In January-February, place a forcing fleece (P30 or P40 winter fleece) directly over your plants in the greenhouse to create a mini-greenhouse within the greenhouse. This technique allows you to gain an additional 2 to 3 weeks on the season and advance the harvest until March.

💡 Tip 2: Artificial photoperiod

Strawberry plants need a minimum of 8 hours of light to flower. In winter, when days are short, you can artificially extend the photoperiod with LED grow lights. 2 to 4 hours of additional lighting in the evening are enough to maintain production.

🐝 Tip 3: Promote pollination

Introduce a small beehive or wild bee hotel near the greenhouse. Open the doors and windows during insect flight hours (9 am-5 pm) during flowering. The quality and regularity of the fruits will be significantly improved.

🌿 Tip 4: Companion planting

Associate your strawberry plants with beneficial plants in the greenhouse:

• Basil: repels aphids and improves the taste of strawberries
• Borage: attracts pollinators and repels aphids
• Garlic: repels many pests and fungal diseases
• Nasturtiums: serve as trap plants for aphids

📦 Tip 5: Preservation and processing

Fresh greenhouse strawberries can be stored in the refrigerator for 2 to 3 days. To enjoy your abundant harvests all year round:

• Freezing: wash, hull, and freeze flat on a tray before bagging. Ideal for smoothies and desserts.
• Jam: an abundant harvest of greenhouse strawberries makes incomparable jams.
• Strawberry vinegar: macerate strawberries in apple cider vinegar for an original condiment.

❓ FAQ - Your Questions about Growing Strawberries in a Greenhouse

🍓 Can strawberries be grown in an unheated greenhouse in winter? Yes, absolutely! Even without heating, a polycarbonate greenhouse maintains a temperature 3 to 5°C above the outside temperature. Most strawberry plants can withstand light frost (-5°C) if their roots are well protected. For everbearing varieties, a simple protective fleece placed over the plants is enough to get through winter without heating. If you want continuous production in mid-winter, a small electric or paraffin heater becomes necessary.

💧 How often should strawberries in a greenhouse be watered? It depends on the season and temperature. In summer (June-August), water every day or every other day. In spring and autumn, 2 to 3 times a week is sufficient. In winter, once a week is generally enough. The golden rule: check the substrate with your finger; it should be moist deep down but never waterlogged on the surface.

🌱 How many strawberry plants for a family of 4? To meet the needs of a family of 4 (about 10 kg of strawberries per season), plan for 40 to 50 plants of everbearing varieties, or 60 to 80 plants of non-everbearing varieties. With a production of 200 to 400g per plant per year for everbearing varieties, these figures give you a solid basis.

🐝 How to manually pollinate strawberries in a greenhouse? It's simple! Every morning during flowering, use a small clean paintbrush (like a watercolor brush) or a toothbrush on each open flower. The circular motion transfers pollen from the stamens to the pistil. You can also simply shake the plants gently to release pollen. Do this preferably between 10 am and 2 pm when the flowers are fully open.

🔄 How long does a strawberry plant last in a greenhouse? A strawberry plant is productive for 3 to 4 years in general. After this period, production decreases, and the plants become more susceptible to diseases. It is advisable to renew a third of your plants each year by taking runners from the most vigorous plants. This way, you always maintain a population of plants in full production.

🌡️ What is the ideal temperature in a greenhouse for strawberries? Strawberries thrive best between 15°C and 22°C during the day, and between 8°C and 12°C at night. This day/night temperature difference (called thermoperiodism) is important for good fruiting and pronounced aromas. Below 5°C, growth stops. Above 28°C, fruit quality deteriorates, and flowers may abort.

🏗️ What size greenhouse for growing strawberries? A greenhouse of 6 to 9 m² is sufficient for family production. For larger production, aim for a minimum of 12 to 15 m². Remember that you can optimize vertical space with shelves and hanging planters, which increases your usable area. To learn more about choosing your greenhouse, feel free to consult our article on how to choose the ideal garden greenhouse.

🎯 Conclusion

Growing strawberries in a greenhouse year-round is one of the most rewarding experiences in sheltered gardening. With the right varieties, controlled watering, adequate ventilation, and a few simple tips, you can produce delicious strawberries almost 12 months a year, regardless of external weather conditions.

The key to success lies in choosing a quality polycarbonate greenhouse that maintains a stable temperature, protects your plants from bad weather, and diffuses light evenly. Combined with the right accessories (automatic irrigation, shelves, growing trays), your greenhouse becomes a true strawberry production machine.

Ready to get started? Discover our range of polycarbonate garden greenhouses now and transform your garden into a fruity paradise all year round! 🍓

Sources: FranceAgriMer, INRAE (National Research Institute for Agriculture, Food and Environment), Centre Technique Interprofessionnel des Fruits et Légumes (CTIFL)