Ultimate Guide to Greenhouse Growing in Winter

A greenhouse creates a perfect microclimate to grow crops in cold climates and protect hardy plants from frost damage.

Greenhouse growing in winter provides warmer soil, steadier temperature, and moderate humidity to promote good crop harvest year-round. To grow the plant inside, hit the greenhouse creating thermal mass, using grow lights and others. 

There are multiple walk-in greenhouses (DIY and commercial) to yield winter harvests of vegetables and herbs.

Can You Grow Plants in a Greenhouse During Winter?

A greenhouse is a microclimate built using an enclosure with a transparent roof and wall to let sunlight in and maintain a warmer indoor climate.

Growing plants, including crops, veggies, flowers, and herbs, is possible year-round in a greenhouse.

You can upgrade your greenhouse to include sun lamps, heating pads, controlled humidity, and air circulation to create a perfect microclimate ideal for all kinds of plants.

Remember, a greenhouse can be beneficial for growing summer or fall crops for extended seasons to keep producing harvests. Besides, it also ensures the following benefits. 

  • To obtain early harvests of tender plants that would require warmer months and give an early start to seedlings.
  • Protecting tender crops from harsh sunlight throughout the summer months.
  • To grow exotic, heat-loving crops like okra, melons, and peppers.
  • Increase the use of sunlight throughout autumn to extend summer crops.

Whether heated or unheated, a greenhouse works the same for all plants by providing an ideal climate and protection from harsh weather and pests!

plants in greenhouse
If you plant growing greenhouse crops, you will require at least one bed.

While it is primarily true that a greenhouse is preferred for warmth-loving crops, the same can be used to grow cold-hardy crops, too -for better yields!

Overwintering plants in an unheated greenhouse will help boost a bigger harvest that would otherwise be difficult in outdoor climates.

And there is always a risk of crop damage from cold frosts or pests that inhabit the outdoor soil!

If you have recently moved to snowy zones, learn if your plant can survive the winter

What to Grow in the Greenhouse?

Plants requiring sun would benefit most from greenhouses as it enables them to make the most of the sunlight.

Alternatively, it can be used for particular winter plants that need a conducive growing environment.

Consider the following plants if you only start to use the greenhouse now. 

PlantsTemperature Requirement
Tender (Dahlias, Begonia, Lilies, Alocasia, Monstera, cucumber, eggplant, pepper, pumpkin, squash, tomato, bay, curry plant, oregano.)60-75°F (15-23°C)
Half Hardy (Zinnia, Cobaea, Amaranthus, Blue sage, beets, spring carrots, lettue, pea, cauliflower, parsley, chives, and thyme lemon)50-55°F (10-12°C)
Hardy (Hawthorn, foxglove, fennel, lavender, potato, turnip, raddish, brussels sprouts, and Daisy)45°F (7°C)

Required Tools to Grow Plants in Winter Greenhouses

Growing plants inside a greenhouse will be very similar to growing them outside. The difference is that the environment is under control.

ToolsSpecifications
Gardening Potting Mix1. Choose moist peat free compost with a thin layer of vermiculite for seedling.
2. Use one part organic material (peat or coir) and inorganic material (perlite, vermiculite) with homemade compost or worm casting.
Plant CagesAttaching cages will help to stake tomato bushes when it begins sprawling.
Rake and TrowelTo mix in potting mix, aerate the compact soil, and fill the gaps without the soil.
LED Grow Light1. Install appropriate grow light wth UV to induce seed growth
2. provide optimal lighting when the sunlight is scarce.
Heating Unit1. Install a portable heating unit that can be controlled by a thermostat.
2. Measure the square footage of the greenhouse before deciding wattage and number of space heaters.
InsulationPolyethylene sheeting or aluminum foil insulation (1/4 thick) to insulate greenhouse wall during winter

Learn how to make a DIY greenhouse first, and here is this video for you!

How to Heat a Greenhouse in Winter For Free?

Winter greenhouse would require setting up an ideal microclimate if you wish to continue growing spring and summer plants like tomatoes and tender or semi-hardy vegetables.

It is especially true for Zone 3, which sees longer, colder months and snow, requiring a few extra measures to warm up the greenhouse.

Alternatively, the unheated greenhouse can protect hardy plants from cold stress, pests, and sudden temperature drop.

Here are some DIY tips for heating your winter greenhouse!

1. Create a Thermal Mass

Creating a thermal mass or heat sink inside the greenhouse will prevent heat from escaping and help circulate the warmth.

Add a water barrel inside the greenhouse and place where it can get the most sunlight, usually the north wall.

2. Use a Heating System

Consider installing a heating system. An electric space heater, Klimaheat, or thermostatically controlled heater would work best to achieve the required warm temperature.

Aim to achieve anywhere between 70-80°F (24-28°C) of temperature to mimic the sunny days inside the greenhouse.

3. Insulate the wall

Insulating the walls would be helpful when you live in a region with long cold months or severe temperature drops.

Use horticultural bubble wrap to insulate the wall, or use horticultural fleece designed to protect the wall.

Alternatively, you can use transparent insulating materials to allow sunlight in.

4. Use Grow Lights

Using grow lights helps with lighting up the space and raising the temperature.

The grow lights would be handy when growing seeds and young plants during fall or winter.

plants in greenhouse
If you plant growing greenhouse crops, you will require at least one bed.

Additionally, the led grow lights will provide UV light which helps produce flavonoids and terpenes, giving vibrant color and a rich smell.

5. Use Solar Water Heating

Install solar panels on the outside and run them underneath the compost pile.

The solar light irradiates the heat-collecting plate to generate hot water, which will heat the soil.

Indoor Rubber plants can be vulnerable in winter so learn to care for them properly. 

Tips to Care for Plants in a Winter Greenhouse

When growing the greenhouse in winter, avoid crowding plants as it can reduce the yield per plant.

Besides, the following considerations will help you care for the plant in the winter greenhouse. 

    • Divide the greenhouse into zones and plant crops that can grow at close distances in one zone and others in another.
    • Use the space underneath benches for plants growing well on the ground. You can use small or large containers for the same.
    • Use HAF fans for better airflow and prevent the risk of diseases.
    • Also, avoid frequent watering as humidity remain constantly high. 
    • Keep fertilizing the plants but in less quantity. 

Wrapping Up… 

You can choose a deep winter greenhouse (depending on the sun to heat the building) or a heated unit, depending on your need.

For example, 14 by 24 feet is a moderate greenhouse size that you can start!

Also, you need to accept the varying growing requirements of plants in a greenhouse and outside. 

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