Can You Use a Greenhouse in Winter?
Yes. A greenhouse can be used year-round in most climates, including winter, though how much it can grow depends on your region, the greenhouse’s construction, and whether you add any supplemental heat. For the broader principles behind rotating crops through the seasons to keep something growing all year, see this guide to vegetables that grow year-round. A greenhouse traps solar heat during the day and slows heat loss at night, which on its own can keep temperatures inside several degrees warmer than outside air. In mild climates, that buffer alone may be enough to grow cold-tolerant crops through winter. In colder regions, an unheated greenhouse will still freeze on the coldest nights, so growers there typically add some form of supplemental heat, extra insulation, or choose crops that can tolerate occasional light frost.
Unheated vs. Heated Greenhouses in Cold Months
An unheated greenhouse (sometimes called a cold frame greenhouse or hoop house) relies entirely on sunlight, thermal mass, and insulation to stay above the outside temperature. This works reasonably well in regions with mild winters or where nighttime lows don’t drop far below freezing. A heated greenhouse adds an active or passive heat source to keep temperatures in a target range regardless of how cold it gets outside, which opens up a wider range of crops but adds ongoing cost and complexity.
Most hobby growers land somewhere in between: an unheated or minimally insulated structure for hardy crops in fall and early spring, with heat added only during the coldest stretch of winter or for frost-sensitive plants.
Will an Unheated Greenhouse Keep Plants From Freezing?
Generally, an unheated greenhouse will keep the air inside noticeably warmer than outside, especially on sunny days and compared to open ground at night, but it will not reliably prevent freezing during a hard freeze or extended cold snap. The exact temperature difference varies by greenhouse design, how well it’s sealed, and local climate, so it’s best treated as a meaningful buffer rather than a guarantee. For genuinely tender plants, growers in colder regions generally add row cover, extra insulation (such as bubble wrap glazing), thermal mass like water barrels, or a backup heat source for the coldest nights.
Common Ways Growers Heat a Winter Greenhouse
There’s no single “best” way to heat a winter greenhouse — the right method depends on budget, climate severity, and whether you need heat occasionally or constantly. Common approaches include:
- Passive solar heating: Using thermal mass (water containers, stone, concrete) to absorb daytime heat and release it slowly overnight. Low cost, but limited in how much temperature swing it can offset.
- Active solar heating: Fans or ducting that move warm air from the sunniest part of the greenhouse to storage or to areas that need it, giving passive solar a boost.
- Compost heating: A compost pile or bed generates heat as it decomposes, which some growers channel into the greenhouse or use to warm a specific growing bed. This is a low-tech, low-cost option, though the heat output is modest and varies with how the pile is managed.
- Forced air heating: Electric or propane heaters with a fan, which can maintain a set temperature more precisely but add ongoing fuel or electricity costs.
- Infrared heaters: Radiant heaters that warm plants and surfaces directly rather than just the air, which some growers find more efficient for spot-heating.
- Gas heaters: Propane or natural gas units are common in larger or commercial greenhouses where consistent heat is needed; they typically need ventilation to manage humidity and combustion byproducts.
- Extra insulation: Double-layer poly film, bubble wrap glazing, or thermal curtains reduce heat loss and can meaningfully cut how much active heating is needed.
Many growers combine two or more of these — for example, thermal mass plus a backup heater for the coldest nights — rather than relying on just one method.
How the Amish and Other Low-Tech Growers Heat Greenhouses in Winter
Amish and other low-tech growers typically favor passive and simple active methods over complex electrical or gas systems, consistent with a general preference for lower-tech, lower-cost solutions. Common approaches reported among such growers include compost-based heating, thermal mass like water barrels or stone, deep mulching and insulation, and sometimes wood stoves for direct heat on the coldest days. These methods generally require more hands-on management than a thermostat-controlled gas or electric heater, but they can keep a greenhouse productive through winter at a lower ongoing cost.
How Warm Is Too Warm for a Greenhouse?
Overheating is a real risk even in winter, since direct sun on a closed structure can push temperatures well above what most vegetable crops tolerate, even on a cold day outside. Most common vegetable crops do best in a general range roughly between the mid-60s and mid-80s°F during the day, and sustained heat much above that can stress plants, reduce flowering and fruit set, or cause wilting — though exact thresholds vary by crop and growth stage. Venting (roof vents, side vents, or a simple door propped open), shade cloth in sunnier months, and thermostatically controlled exhaust fans are the usual tools for keeping a greenhouse from overheating, and winter growers should still check on ventilation on bright, sunny days even when it’s cold outside.
What to Grow in a Winter Greenhouse
Cold-tolerant leafy greens and cole crops are the most reliable winter greenhouse choices in most climates. Lettuce, spinach, kale, and various Asian greens generally hold up well to the cooler, lower-light conditions of winter, even with minimal supplemental heat. Root crops like carrots, radishes, and turnips can also do reasonably well in many unheated or minimally heated setups. Warm-season crops like tomatoes, peppers, and cucumbers generally need both added heat and supplemental light to perform well in winter, since both temperature and day length drop below what they typically need. For a deeper look at one of the most common winter greenhouse crops, see our guide to growing lettuce in a greenhouse during winter.
If you’re in a particularly cold or low-light region — far northern latitudes with short winter days — a greenhouse alone may not be enough for some crops, and supplementing with indoor growing under lights can fill the gap. Our guide to indoor gardening in cold climates like Maine and Alaska covers that approach in more detail.
A Basic Winter Greenhouse Checklist
- Know your local winter lows and how much buffer your unheated structure realistically provides.
- Decide whether you need supplemental heat, and if so, pick a method that matches your budget and how hands-on you want to be.
- Add insulation (double glazing, bubble wrap, thermal curtains) before investing in active heating — it often has the best cost-to-benefit ratio.
- Plan for ventilation on sunny days, not just heat on cold nights.
- Choose crops suited to the light and temperature you can realistically maintain, leaning on cold-tolerant greens and roots unless you’re adding both heat and supplemental lighting.