Planting Guide · December 2025 · 5 min read
Winter greenhouse growing extends your harvest season and captures premium prices for fresh produce when outdoor gardens are dormant. Hardy greens like spinach, lettuce, and kale can thrive in unheated or minimally heated structures throughout the coldest months. With the right crop selection and light management, a winter greenhouse becomes one of the most profitable square-footage investments on the farm.
Spinach is the undisputed champion of cold-weather greenhouse production, tolerating temperatures down to 15°F without significant damage. Lettuce varieties like winter density and rouge d'hiver handle cold well, and kale actually sweetens after frost exposure.
Day length, not temperature, is often the limiting factor in winter production. When daylight drops below 10 hours, plant growth stalls regardless of warmth. LED grow lights providing 12-14 hours of total light can keep crops growing actively through December and January.
Heating costs vary dramatically by region and fuel source. Propane heating can cost $2-5 per square foot per winter season. Many growers find that quick hoops or row covers inside the greenhouse create a double-layer effect, raising minimum temperatures 5-8°F without added fuel cost.
Quick hoops are inexpensive wire or conduit arches draped with row cover fabric inside the greenhouse. This greenhouse-within-a-greenhouse approach creates a microclimate that protects crops from the harshest cold snaps. Install hoops 4 feet apart and use medium-weight row cover for best results.
🌱 Plan your planting dates with our free tool:
Try the Planting CalculatorWinter greens command premium prices at farmers markets and restaurants when outdoor supply disappears. Spinach and salad mix can bring $8-12 per pound in winter compared to $4-6 in summer. Even with reduced yields and slower growth, the price premiums make winter greenhouse production highly profitable for market growers.