Extending the Growing Season with Winter Greenhouses

Greenhouses create year-round sanctuaries for growth.

Extending the Growing Season with Winter Greenhouses

December 12, 2023

Before embarking on your winter greenhouse gardening journey, it's crucial to note that while greenhouses offer an ideal haven for year-round plant growth, they require diligent maintenance and monitoring. Effective temperature control, ventilation, and proper insulation are vital to safeguard your plants from extreme winter conditions.

While frigid temperatures and snow may halt outdoor gardening activities, the show goes on inside the nurturing sanctuary of the winter greenhouse. These structures create microclimates allowing gardeners to harvest fresh produce year-round, even in cold northern regions. From hoop houses enclosing raised beds to Dutch glass palaces glittering with icicles, greenhouses enable connections between people, plants, and nature’s cycles during dormant seasons.

Introduction to Greenhouses for Winter Growing

Introduction to Greenhouses for Winter Growing

A greenhouse refers to a transparent enclosure harnessing solar energy to warm the interior for cultivating plants. Greenhouses take on various forms from temporary hoop tunnels stretched over growing beds to elaborate glass atriums attached to homes. They allow gardeners to customize interior climates, overcoming challenging external conditions. With adequate glazing, insulation, and climatic controls, greenhouses can maintain temperatures suitable for plant growth year-round, even in cold climates.

While outdoor gardening ceases during frigid winters, greenhouse gardens burst with life. They offer sanctuary from the elements for both plants and people. Winter gardens confer space for peaceful reflection, joyful workshops, and gathering harvests despite barren landscapes outdoors. And through these bonds nurtured over winter months, people reconnect with nature’s cycles and community ties anchored to the land. The future points toward greenhouses underpinning sustainable agriculture and community resilience alike.


Designing Greenhouses for Winter Growing

To shelter plants during freezing winters, greenhouses must retain heat while maximizing light for adequate plant growth. Design elements conferring winter performance include:

Glazing Materials

Glass: Provides maximum sunlight transmission but poorer insulation than other glazes unless double-paned.

Polycarbonate Panels: Offer excellent durability, insulation, and light diffusion. Resists hail storms and snow loads better than glass.

Poly Film: Low cost option for temporary structures but replaces frequently. Can achieve double inflation for higher insulation when two layers separated by air gap.

Insulation Methods

Bubble Wrap: Stapled to interior walls, bubble wrap boosts insulation while allowing light penetration.

Water Barrels: Dark containers filled with water absorb heat during daytime then release warmth at night.

Compost Piles: Active piles generate heat while breaking down nutrients for future plant feeding.

Thermal Mass Walls: South-facing walls constructed from heat-absorbing materials (concrete, water bottles, etc) soak up daytime heat and radiate warmth into the night.

Shape and Angle

Hoop House: Semi-circular shape readily sheds snow accumulation while allowing solar gain.

Lean-To: Angled design attached to building takes advantage of radiant wall heat from structure.

Geodesic Dome: Rounded design provides excellent snow shedding, durability, and heat distribution through efficient shape.

With thoughtful incorporation of such elements, greenhouses transform into synergistic ecosystems nurturing plant and human health even as winter winds billow outside.

Creating a Winter Greenhouse Microclimate

Creating a Winter Greenhouse Microclimate

While preventing deep freezes, greenhouses must also maintain temperatures, humidity and airflow at levels promoting healthy plant growth without overheating. Monitoring conditions and tweaking them for optimal winter production involves:

Temperature Tracking

Install maximum-minimum thermometers indicating temperature swings. Lower thresholds for leafy greens sit around 30-40°F before growth halts while tomatoes cease below 50°F. Fluctuations induce plant stress.

Use thermostats controlling heaters and exhaust fans automatically maintaining ideal temperature ranges.

Ventilation & Humidity Balancing

Crack vents daily allowing ample air circulation preventing diseases. Weather stripping minimizes drafts.

Promptly fix condensation buildup promoting fungal issues through ventilation and dehumidification.

Ensure heaters have adequate capacity for building volume and have safety controls preventing overheating.

With adequate insulation, 21,000 BTU heaters can maintain 30°F inside when it is 0°F outside. But any heating system demands energy, so first implement passive solar techniques before supplementing with active heaters during the coldest stretches.

Manually clear snow accumulating on structures without compromising integrity. While some snow cover insulates, excessive weight damages infrastructure. Clear paths to doors while allowing some picturesque fringes to remain.

Through controlling the indoor environment, greenhouses allow one to transcend outdoor growing limits in creating favorable microclimates, whether the intention be protecting delicate perennials or boosting winter vegetable yields.

Selecting Optimal Winter Greenhouse Plants

Selecting Optimal Winter Greenhouse Plants

Cool Season Vegetables

Leafy Greens – kale, lettuces, spinach, arugula, Asian brassicas
Root Vegetables – carrots, turnips, beets, onions
Peas & Beans (sheltered microclimate prolongs harvest)

Overwintering Herbaceous Perennials

Ornamental grasses, ferns, hellebores (protect until established)

It is better to underplant beds for optimal maturation and air circulation than cramming excess seedlings. Even in greenhouses, plants grow more slowly through winter. Account for plants needing full sun versus partial shade or protection when organizing beds and benches by exposure.

And don’t forget seasonal infrastructure! Install trellises for vertically trained peas and cucumbers to save space while preventing soil contact and rot. Incorporate swiveling benches allowing rearrangement for optimal light exposure as sun angles shift. Such adaptive measures make greenhouses effective for year-round harvesting.






Join our Newsletter

Become an integral part of our community of fellow plant lovers, where every edition is a botanical adventure waiting to unfold. Discover exclusive gardening tips, stay updated on the latest plant trends and answering readers questions on Ask Seeds!


    About the Author


    Cameron is a plant journalist who loves everything green and eco-friendly. He writes for various publications about the benefits of native plants, such as enhancing biodiversity, reducing water use, and supporting pollinators. He also runs a special column about Native Plants of the Month on Cameron believes that everyone can make a positive difference one seed at a time.





    Join our Newsletter

    Become an integral part of our community of fellow plant lovers, where every edition is a botanical adventure waiting to unfold. Discover exclusive gardening tips, stay updated on the latest plant trends and answering readers questions on Ask Seeds!

      Ask Seeds LEAFY LETTERS