The Essential Structure for Gardening Even in The Harshest Winters - The Greenhouse for Inner-city and for the Countryside
The single most important structure for gardening in cold climates is a well-insulated greenhouse.
It offers the solution to the region’s biggest challenge: a lack of warmth and the threat of frost damage.
You can use a greenhouse to extend the growing season in two ways:
- As a nursery: Start seedlings inside and transplant them outdoors as soon as they are mature enough.
- As a growing space: Grow plants entirely within the structure.
Greenhouse: A structure designed for plant cultivation that regulates internal temperature and humidity while allowing sunlight to enter for photosynthesis. By covering the structure with transparent materials (like glass or plastic), sunlight passes through and warms the interior. The material then traps the resulting heat by blocking infrared radiation from escaping and preventing warm air from mixing with the cooler outside air. This phenomenon, known as the greenhouse effect, causes the internal temperature to rise.
Early precursors to greenhouses date back to 30 AD in Rome. Emperor Tiberius reportedly demanded cucumbers year-round, leading to the invention of specularia—frames covered with translucent sheets of selenite (a mineral also called lapis specularis).
In this edition, in 4 minutes or less:
#1 Why the Greenhouse is so important
#2 Comprehensive Greenhouse for a farm, a homestead, or a shelter
#3 Greenhouse for Inner-City Dwellers with Limited Space
Why the Greenhouse is so important
During winter in temperate climates, it is so cold that everything enters dormancy (stops growing) and plants remain dormant for many weeks after the start of spring until the soil warms up.
Moreover, frost and snowfall can occur well into spring, killing any new, tender plants you are growing. Consequently, you lose critical time at the start of the season waiting for the soil to defrost, and you risk exposing young plants to late snowfall and frost, potentially losing your efforts entirely. At the end of the season, just as everything is thriving, the coming winter cuts the growing period short.
A greenhouse not only allows you to jump-start your season and protect young plants from cold snaps but also extends the viable growing conditions at both the beginning and end of the year by creating a warm, protected microclimate.
Of course, you will face lower sunlight intensity and shorter days during winter, early spring, and late autumn. This will still slow down plant growth inside the greenhouse, but that is simply the reality of the region - you must make the best of the warm period with the available sunlight. However, the light intensity deficiency in this climate becomes an advantage during the peak of the growing season. The light reaches the optimal level for plant photosynthesis without becoming excessive, as it often does in the tropics. In temperate zones, plants rarely reach the point of light saturation, where they shut down growth, and, coupled with long summer days, the growth rate of plants in temperate zones is immense.
Light Saturation: The light intensity threshold at which a plant’s photosynthetic rate reaches its maximum and does not increase with further increases in light. Beyond the saturation point, additional light provides no growth benefit and can lead to photoinhibition, a condition where excess light energy damages the photosynthetic apparatus of the plants(a common issue in the tropics), resulting in no growth until the situation of excess light changes and the plant recovers.
In the tropics, there is no dormant period due to cold, so you can grow year-round - a well-insulated greenhouse is not essential. However, excessive sunlight intensity and heat can hinder plant growth or kill them. So, to prevent photoinhibition (which shuts down photosynthesis) and excessive heat, it is essential to create shade for plants in the form of a shadehouse, overstory, or trellis (as discussed in the tropical home gardening series).
In temperate climates, a solid greenhouse is essential. Fortunately, there are many efficient and viable designs for creating a sustainable practice, ranging from house-attached structures requiring significant investment to free-standing, completely DIY options. All can be elegant and efficient.
Comprehensive Greenhouse for a farm, a homestead, or a shelter
This design was created by the New Alchemy Institute in Massachusetts (USA) for a large bioshelter.
It is a comprehensive design attached to an existing house, utilizing its heating and infrastructure. It incorporates many elements that make it extremely resilient:
- Insulated floor: Separated from the earth outside the walls.
- Thermal mass: Standard 200 L (53 gallon) water drums that store heat. These can also be used to raise fish and grow hydroponic vegetables.
- Animal integration: Areas beneath benches can house rabbits, guinea pigs, poultry, or other animals to provide heat and additional yield.
- Active composting: A compost pile inside the greenhouse provides heat and builds soil. The pile can be assembled just outside the greenhouse to aid insulation.
- Adjustable roofing: The roof features awning blades that allow sunlight to enter during spring, winter, and autumn to warm the interior.
- Raised beds: Designed for growing vegetables.
- Vertical space: Because it is attached to the house and the roof follows the house’s slope, it provides enough headroom for berries and fruit trees.
- Infrastructure integration: Possibility to integrate house infrastructure with the greenhouse (e.g., water pipes from the shower can be directed to growing beds after filtration).
Greenhouse for Inner-City Dwellers with Limited Space
This design was created by Dr. Sonja Wallman specifically for inner-city dwellers in densely populated areas like Berlin, where she developed the project.
Its most interesting characteristic is that it requires no additional heating. Within a 20 m² greenhouse, it is possible to produce 70% of the fruit and salad needs for 3–4 people, if you follow this conditions:
- Attached to an existing house (not free-standing).
- Oriented toward the sun, following the exact sun angles of summer and winter.
- The house wall and double-sheeted glass create extensive heat insulation.
- Uses raised, insulated beds.
- Acts as a “suntrap” and buffer zone, trapping energy.
- The house acts as an air filter, improving air quality inside.
In winter, the sun heats the rear wall of the house, which acts as a heat storage unit. The heat collected during the day radiates into the house and greenhouse during the evening. In summer, the insulated solid part of the sloping roof prevents the rear wall from receiving direct sun rays. Ventilation flaps direct airflow.
Preparation for summer and winter takes one weekend of work. Upkeep and watering take about 20 minutes per day.
Organic waste is fed to composting worms, and together with mulch, the soil is regenerated.
How to Plant: Along the house wall, plant herbs. Along the outer glass wall, plant different cabbages and lettuces. When the soil temperature reaches 23°C, summer planting with annuals can begin. The winter plants are then replaced one by one with tomatoes on trellises, cucumbers, pole beans, nasturtiums, basil, and others. Hardy or perennial plants remain in their place.
Last but not least, Sonja Wallman created a specific list of plants for her inner-city greenhouse.
In the next newsletter, we will discuss free-standing greenhouses, which do not require attachment to any structure.
- Hot Beds
- Animal-Heated Greenhouses
- Mini Greenhouses (Cloches)
These options are even more modular and adaptable than the ones described here. They are suitable for everything from a small, completely handmade garden project to large-scale gardening or farming (to feed a community). If you source the materials yourself, they can be built at no cost.
They stand on their own and can serve as the foundation for any garden.
