how to grow vegetables in the winter in a greenhouse


Growing your own vegetables in the winter can seem like an impossible task, especially if you live in an area that experiences cold, snowy winters. However, with the use of a greenhouse, you can enjoy a bountiful harvest of fresh vegetables even during the colder months. In this article, we will cover everything you need to know to successfully grow a variety of vegetables in your greenhouse over the winter season.

Some key benefits of winter greenhouse vegetable gardening include:

Enjoying homegrown produce year-round. With a greenhouse, you don’t have to wait for spring to start harvesting fresh veggies.

Saving money on grocery bills. You’ll spend less buying veggies at the store when you can harvest them from your own greenhouse.

Higher nutritional quality. Homegrown produce is often more nutritious than store-bought since it’s fresher and retains more vitamins and minerals.

Therapeutic benefits. Gardening and working with plants is proven to reduce stress and enhance mood. Growing veggies over winter provides these benefits year-round.

Beating seasonal market prices. Many farmers market veggies are more expensive in winter since greenhouse production of these crops is limited.

Convenience and access. A backyard greenhouse means you’ll always have a ready supply of fresh veggies without having to travel to the store.

So with the right greenhouse setup and growing techniques, you’ll be enjoying homegrown winter vegetables in no time. Let’s explore the specifics of successfully growing a variety of veggies over the colder months.

Choosing a Greenhouse

The type of greenhouse you choose will depend on factors like your climate, available space, and budget. Here are some common greenhouse options.

Freestanding Greenhouses: These portable structures can be placed directly on the ground or raised on wooden platforms. They come in wood, aluminum, plastic, or fiberglass frames with glazing options like glass, polycarbonate, or clear plastic sheeting. Prices range from a few hundred dollars for small plastic models up to several thousand for large DIY wood-framed greenhouses.

Hoop Houses: Also called high tunnels, these are quonset hut style greenhouses made from PVC pipes or metal posts covered with a single sheet of durable plastic sheeting. Hoop houses provide good protection at a low cost and can span 10-30 feet wide by any length. DIY kits start around $100-300.

Garden Shed Greenhouses: For smaller spaces, consider converting an existing garden shed into a mini greenhouse by installing glazing on the walls and roof. Old windows and doors can be reused for this affordable retrofitting project.

Wall-Mounted Greenhouses: These modular panel systems mount directly on house walls or fences, utilizing the existing structure for support. Panels interconnect to construct floor-to-ceiling glazing in compact spaces. Cost can range from a few hundred dollars up to $1,000+ for larger systems.

Regardless of which greenhouse you choose, look for units constructed with durable materials rated for temperature extremes. Make sure the base foundation or anchoring system is secure enough to support heavy snow loads in winter. Proper ventilation and shading options will also be important for plant health and temperature control.

Selecting the Greenhouse Location

Carefully choose a spot for your greenhouse that will maximize sun exposure and facilitate plant care year-round. Here are some key location considerations:

Orient the long side of a freestanding greenhouse west to east for optimal sunlight distribution inside throughout the day. East is second best if space is limited.

Allow for at least 6 feet of clearance on the south side for adequate sun exposure, plus easy access for working and maintenance.

Higher elevations drain water better, but avoid slopes prone to flooding or sliding in heavy snow.

Place on level, firmly compacted soil for structural stability. Consider gravel, concrete, or wooden foundation platforms if the ground is uneven, rocky, or prone to sinking.

Ensure good drainage slopes water away from the greenhouse structure. Raise beds or platforms further if needed.

Provide adequate workspace around the greenhouse for plant care, watering, sitting areas, tool storage, etc.

Consider proximity to your home and electricity/water sources for convenience during winter.

Screen off windy, exposed areas prone to drafts and higher wind loads from snow and storms.

Place out of the typical path of winter foot traffic and recreation areas to avoid accidental damage.

With the greenhouse installed in its ideal south-facing location, you’ll be all set to begin planting and enjoying your winter harvest!

Preparing the Soil
Nutritious living soil is crucial for supporting healthy plants and maximizing your winter vegetable yield. Start prepping the soil 6-8 weeks before your first planned winter planting. Here are some soil preparation tips:

Remove any existing weeds and weed roots that could harbor pests or diseases. Till or dig the soil 8-12 inches deep.

Incorporate 2-4 inches of organic matter like compost, well-rotted manure, or leaves. This enhances soil structure and nutrition. Work it into the top 8 inches.

Consider raised beds if your soil drains poorly. Build 12-16 inch tall frames from untreated wood, stones, or concrete blocks. Fill with nutrient-rich potting mix or garden soil.

Take a soil sample to analyze pH levels, nutrient deficiencies, and heavy metal or contaminant content if unknown. Adjust the pH as needed.

Add timed-release organic fertilizers like bone meal or rock phosphate when prepping in fall to feed emerging winter plants slowly.

Rake the soil smooth and break up any clumps prior to planting. This improves aeration, drainage and root penetration.

With fluffy loam soil teeming with microbes and nutrients, your greenhouse plants will send down deep, stabilizing roots during their winter growth. Check the soil moisture levels regularly to avoid soggy or dry soil conditions as plants develop.

Heating Your Greenhouse

Consistently warm temperatures between 60-75°F are important for healthy winter vegetable growth indoors. Without adequate heating, cold hardy crops like leafy greens and root veggies may bolt, rot or go dormant. Here are heating system options:

Oil-filled or ceramic heaters cost effectively produce infrared heat with thermostatic controls for accurate temperature regulation. Place throughout greenhouse for even warming.

Solar thermal heating uses insulated tubes and a collector mounted on the greenhouse roof to transfer sun-warmed liquid into radiant floor heating inside.

Wood burning stoves provide long-lasting heat efficiently if the greenhouse has an exterior chimney installed to code standards. Monitor for safety.

Natural gas or propane whole-house furnaces efficiently heat attached greenhouses especially on cold nights or during prolonged sunless periods. Install per code.

Electric heating cables, mats or tanks safely distribute warmth under bench beds and raise seedling trays above soil for climate-controlled germination.

Insulate the greenhouse structure and use energy efficient heating systems placed throughout for even warmth distribution. Seal any areas prone to drafts. Monitor day and night temperatures closely with electronic thermometers and moisture sensors. Automatic vents, fans and shade cloths also help maintain optimal conditions.

Controlling Moisture

Too much condensation or inconsistent humidity levels are inviting conditions for plant disease and rot. Proper moisture control is important in the greenhouse this winter. Some effective strategies include:

Ensure adequate ventilation and airflow throughout the greenhouse daily. Open a top vent or side panels when temperatures rise above 60°F.

Install removable polycarbonate roof panels over ridge ventilation spaces that automatically open when humidity surpasses preset levels.

Use dehumidifiers inside smaller greenhouse areas to reduce moisture, especially on cold nights when condensation is most likely to occur.

Place heaters off the ground level on tables or shelves to allow airflow around them and prevent moist soil conditions directly below.

Consider a whole-air vent and fan circulation system with adjustable thermostats to passively ventilate and prevent moisture buildup.

Apply water carefully to the soil surface rather than misting leaves directly. Water only when top inch or two of soil is dry to prevent foot rot diseases from excess moisture.

Adjust heating temperatures or humidity levels, increase ventilation or utilize desiccant materials like lime if condensation does persist in problem areas.

Maintaining adequate ventilation coupled with careful moisture control will allow your greenhouse crops to thrive without the risk of fungal rotting over the wetter winter period. Check foliage daily for the first signs of moisture-related diseases and adjust conditions accordingly.

Choosing Winter Vegetable Crops

While selection varies depending on your climate zone and frost dates, here are some of the best vegetables suited to winter greenhouse growing:

Leafy Greens: Lettuce, spinach, kale, Swiss chard, arugula – Fast growing and tolerant of cooler conditions. Pick individual outer leaves for continual harvests.

Root Vegetables: Carrots, beets, radishes, turnips – Plant dense successions every 1-2 months for ongoing small roots all winter long.

Herbs: Basil, parsley, cilantro, dill – Grow in containers or beds near the warm greenhouse walls. Pick often for fresh flavor.

Leaf Vegetables: Cabbage, broccoli, cauliflower – Grow cold hardy varieties over winter for spring harvests of fuller heads.