Growing onions in a greenhouse is a great way to get fresh greens and quality bulbs almost all year round. However, for successful cultivation, it is important to choose the right variety, provide optimal conditions and comply with all agricultural practices. In this article, we will consider how to properly plant onions in a greenhouse, care for them and what nuances are important to consider when growing in closed ground.

Selecting an onion variety for greenhouse cultivation

The onion variety must be selected based on the purpose of cultivation: for greens or for bulbs.

The best varieties for growing in a greenhouse:

• For greens: "Batun", "Shallot", "Slizun", "Multi-tiered onion" - grow quickly, give several harvests per season.
• For forming turnips: "Strigunovsky", "Exhibition", "Red Baron", "Stuttgarter Riesen" - resistant to temperature changes, form dense bulbs.
• Hybrid varieties: "Centurion F1", "Hercules F1" - give a stable harvest and are less susceptible to diseases.

How to choose the right variety?

• Photoperiod: Onions are divided into short-day and long-day. Short-day onions grow better in a greenhouse, as they require less sunlight to form a bulb.
• Propagation method: Seed onions take longer to grow, but are more resistant to diseases, while sets produce a harvest faster.
• Early maturity: For year-round cultivation, it is better to choose varieties with a short growing season (60-90 days).

Expert advice: If you grow onions for greens, choose varieties with a strong root system - this will extend the growing season and allow you to get several cuts per season.

Preparing the soil and beds in the greenhouse

Onions prefer loose, fertile soil with good air permeability and neutral acidity (pH 6.5-7). Avoid areas with heavy clay soil, as it impairs root growth and can cause bulb rot.

Soil preparation stages:

1. Deep digging – loosening the soil to a depth of 20-25 cm, removing stones and remains of old plants.
2. Enrichment with organic fertilizers – humus (4-5 kg/m²), compost, ash (100 g/m²) to improve nutrition.
3. Application of mineral fertilizers – superphosphate (30 g/m²), potassium sulfate (20 g/m²), ammonium nitrate (15 g/m²) for active growth of greenery and formation of large bulbs.
4. Soil disinfection – before planting, it is recommended to treat the soil with a solution of copper sulfate (1 tablespoon per 10 liters of water) or biofungicides (“Fitosporin”).

Formation of beds:

• The optimal height of the beds is 10-15 cm, width – 80-100 cm.
• The distance between rows is 20-25 cm for onions, 10-15 cm for greens.
• The depth of the bulbs is 2-3 cm for greens, 3-4 cm for onions.

Expert advice: To increase yields, add vermiculite to the soil before planting – it will help retain moisture and improve the soil structure.

When to plant onions in a greenhouse?

The exact timing depends on temperature conditions:

• In a heated room greenhouse Onions can be grown all year round, planting every 2-3 weeks.
• In an unheated greenhouse, planting is carried out in March-April or September-October.
• Onion sets are planted for bulbs in February-March in order to obtain marketable bulbs by May.
• Green onions can be planted in cassettes or containers throughout the season.

Expert advice: Before planting, the seed onions are warmed up at a temperature of +35…+40°C for 8-10 hours – this reduces the likelihood of bolting.

Caring for onions in a greenhouse

Main parameters:

• Temperature: +18…+22°C for greens, +14…+18°C for turnips.
• Lighting: minimum 12-14 hours, additional lighting in winter.
• Humidity: 60-70%.

Watering:

• The optimal regimen is once every 5-7 days.
• The water should be warm (+20…+25°C), watering is carried out at the root.
• Watering is stopped 10-14 days before harvesting to allow the bulbs to ripen.

Top dressing:

1. After planting – urea solution (15 g/m²) to stimulate root growth.
2. During active growth of greenery – potassium fertilizers (20 g/m²) to strengthen tissues.
3. Before the bulbs ripen, apply superphosphate (30 g/m²) to ensure density and preservation of the harvest.

Expert advice: Spray the plants with a weak solution of potassium permanganate once every two weeks – this will strengthen the immune system and prevent the development of fungal diseases.

Protection from diseases and pests

Main diseases:

• Downy mildew – causes yellow spots on leaves.
  • Control: treatment with Bordeaux mixture (1%).
• Neck rot - affects bulbs, especially in high humidity.
  • Prevention: adhere to the watering regime, dry the bulbs before storage.

Main pests:

• Onion fly - larvae damage bulbs.
  • Protection: mulching with ash, treatment with tobacco dust.
• Thrips - feed on plant juices and slow down growth.
  • Control: spray with infusions of garlic and onions.

Expert advice: Regular ventilation of the greenhouse reduces humidity and prevents the spread of fungal infections.

Growing onions in a greenhouse

Growing onions in a greenhouse – is an effective way to get fresh greens and bulbs. The main thing is to choose the right variety, follow the watering and fertilizing regime.

If you want to create ideal conditions for growing onions, choose greenhouses from NovaTeplitsa. They provide reliable plant protection and create an optimal microclimate. Check out the models on our website and grow onions with maximum efficiency today!