But it’s not only plants that need heat to keep growing through winter. Heating your greenhouse protects tender plants from the worst of the winter weather, but rising energy costs and environmental concerns make it important to do the job right.
If you live in about USDA zone 8 south, having a simple single-layer greenhouse can get you through the winter easily. Here are some tips on how to heat a greenhouse and keep your plants warm without it costing the earth. Simple and it works. Warmer temperatures are actually detrimental to their growth. Another way to maximize the warm air that you can capture inside your greenhouse during a cold winter is by using bubble wrap to insulate the translucent walls of your greenhouse. If your customers have a greenhouse, offer these tips on how to keep it warm and useful during the winter.

Insulate with bubble wrap You probably have bundles of this common, inexpensive material around your house from mail order parcels, and it’s perfect as greenhouse insulation.
Does your greenhouse need a heater? Step 2 Clean the jugs or barrels thoroughly with hot, soapy water and rinse well with clean water. That’s why an efficient and properly-sized supplemental heating system might just be necessary for your winter greenhouse if required for the crops you are growing. These two cold season vegetables need a temperature between 45-55F at night and between 50-70 during the day.

Check out all the details on Total Landscape Care. Here's the one I bought a couple of years ago. Greenhouses allow gardeners to grow plants during cooler temperatures by trapping the sun’s energy inside and then utilizing the soil beneath to trap radiant warmth. You should adjust your automatic greenhouse vent openers to open minimally. For colder climates, you must have at least 5 gallons of water per square foot. However, some plants require even more heat to thrive, so you may need a heater. They are best started very early in the greenhouse, in mid-late winter, for a spring planting. With your necessity to take in the warm sun hours as the days shorten, be sure to take down your shade cloth no later than October. If your greenhouse is located in a warm climate—such as that found in the southern United States—you will need 2 or more gallons of water per square foot of glass. Winter Greenhouse Planting Cabbage & Broccoli.