Winter Gardening & Greenhouses


In a lot of climates winter gardening is not a topic of conversation due to the cold temperatures and rough conditions. A practical way to provide an environment for plants to grow, where they normally would not be able to survive, is with a greenhouse. Knowing about a greenhouse's functions, important factors, sizing and best plants to grow will help you get a better understanding of your winter gardening options.

Functions: Greenhouses provide many uses for growing out of season plants and winter gardens. Besides providing shelter from cooler temperatures or harsher winters, a greenhouse can allow you to get a jump start on sowing seeds for spring planting. It provides a stabilized growing environment and protects from diseases and pests. A greenhouse uses heat from the sun to provide a place to grow plants, making the inside temperatures warmer than outside.

Important Factors: The amount of light the greenhouse will be exposed to is just as big of a factor as the heat. Grow lights or even shop lights with a high wattage bulb will be sufficient to provide light and heat.



Knowing how cool your winters get will determine the plants you can grow successfully as well as the supplies you need to do so. Research the type of plants you are planning on growing in your greenhouse to find out how warm or cool you will need to keep the temperature. A key aspect to know is during a typical sunny day your greenhouse will be 20-40 degrees warmer than outside. On the other hand, at night your greenhouse can cool down to the same temperature as outside. If your plants require warmer climates, you will want to provide supplemental heat in your greenhouse.

If your greenhouse will require additional heating, the best idea is to install a heater with a fan and thermostat. This way it will control the heat up to a certain temperature at the same time as dispersing the heat throughout the greenhouse.

If your winters consist of sub-freezing temperatures, your best option is to go with a greenhouse with twin wall polycarbonate. These two layers will have a better R-Factor and will keep the heat trapped in for a longer period of time.

Size: The best size to build is larger than what you are planning; larger greenhouses generate more heat by capturing more of the sun's rays. Also keep in mind to allow enough room to have a walking path by your plants. Often times, people make the mistake of planning out the size they need, but do not allow an area to access their plants. Make sure you have a plan of the number of plants you intend to grow, if you will have sinks or shelves and if the utility costs for heating and lights will be within your budget.


Best Plants To Grow:

Vegetables: lettuce, peppers, spinach and tomatoes

Lettuce is a cool season crop. Seeds will germinate in temperatures as low 40 degrees and will grow in temperatures ranging from 45 degrees to 65 degrees. Lettuce can take from 45-70 days to mature.

Peppers length to mature ranges from 50-110 days, so if you are planning on transplanting into an outdoor spring garden, plan accordingly.

Spinach grows best in cool weather and seeds can germinate in soil temperatures as low as 35 degrees.

Tomatoes like temperatures above 55 degrees, so if you are planning on having a cooler greenhouse, it is suggested you do not plant tomatoes.



Flowers: cyclamen, freesias, fuchsias and geraniums

Cyclamen plants like high humidity and moist soil. To keep the soil from draining well you can add peat moss or compost.

Freesias like warm climates during the day and low temperatures (40-45 degrees) at night. They can grow up to a foot and a half high so plan accordingly.

Fuchsias are plant that can easily be grown in a greenhouse and look great in hanging baskets. They do require well drained soil in order to reach its maximum growth.

Geraniums like soil temperatures around 60 degrees and thrive on sunlight. If there is a lack of natural light place fluorescent lights 10-12 inches above your plants.


Having your own greenhouse ensures you will be able to have plants year round. It is the most practical solution to harsher winters and cooler temperatures. Knowing the functions of a greenhouse, the important factors, the size you need and the best plants to grow, you can have a successful winter growing season.