Winter harvesting of fresh vegetables in Slovenia is possible without purchased heating, if you choose the right crops. A polycarbonate greenhouse gives plants +5-8°C above the outside temperature, which is enough for resistant crops.
Why winter crops in a greenhouse
Three key reasons:
- Low or zero costs, resistant crops do not require heating
- Healthy nutrition, fresh vegetables in winter, when the supermarket is full of imported tomatoes
- Active soil, soil with plants does not freeze as much, works earlier in spring
Important condition: the greenhouse must be polycarbonate or glass. PE foil does not retain enough heat in winter.
Best winter crops
Classification by frost resistance:
Most resistant (up to -10°C outside):
- Lamb's lettuce (Valerianella), king of winter harvesting
- Wild rocket (Diplotaxis), survives under snow
- Spinach "Polar" / "Winter Giant", thick leaves
- Chinese cabbage "Pak Choi", fast, frost-resistant
Moderately resistant (up to -5°C outside):
- Red winter beet "Rouge d'Hiver"
- Endive "Bubikopf"
- Radicchio "Trevisano"
- Winter carrot
Conditionally resistant (below 0°C in the greenhouse, but we must protect):
- Cherry tomato (young seedlings)
- Winter cabbage (kale, broccoli)
- Leek for spring
Planting schedule
Ideal seasonal calendar:
- September: lamb's lettuce, rocket, spinach, direct sowing
- October: beet, endive, seedlings or sowing
- November: additional sowing of lamb's lettuce and spinach for successive harvesting
- December: no sowing, only harvesting
- January: microgreens on window sills
- February: first tomatoes and peppers in a home window for March transplanting
More about spring planting in the article March tomato planting.
Care during winter
Winter care is simple:
- Watering: 1-2 times a week, only in the sun (so it doesn't freeze at night)
- Ventilation: open for 30 minutes on a sunny day (-3°C or warmer)
- Harvesting: only in the sun (plants are sensitive to damage when frozen)
- Soil: mulch with straw or leaves (root protection)
Additional protection in extreme frost
In case of forecast -15°C or lower:
- Double protection: cover plants with agro-foil (P17 or P30)
- Water barrels: 200 L barrels absorb heat during the day, release at night
- Compost pile in the greenhouse, fermentation releases 30-40°C heat for 3-4 weeks
- Candles in glass jars (not open!) for emergency cases, raises temperature by 2-3°C
"The essence of a winter greenhouse is not warm air, it's preventing root freezing. Mulch and soil are more important than heating.", gardener and professor of agronomy
With well-planned winter planting, a family of four can cover all their needs for salads and greens from December to March, completely without purchase.
Polycarbonate for winter hardiness
Our polycarbonate greenhouses have 4-6 mm double-walled panels, which retain heat 3 times better than PE foil.
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