Having a greenhouse allows you to start your garden seedlings early in the season. Large greenhouses can also be used to prolong the life of potted plants, or even allow you to maintain plants all year. Your greenhouse may be a simple plastic-covered shelf or an elaborate heated walk-in model. No matter what type you use, your greenhouse does need some shade and adequate ventilation.
While you do want your plants to receive sunlight and warmth, your need to protect them from too much heat. Your shading needs will depend on your geographic area, the location of the greenhouse on your property and the types of plants you wish to grow. If you are located in the south, plan to achieve a shade density of 70 to 80 percent. Northern areas only need 40 to 60 percent shade density.
A tarp or fiberglass shield can be used to create the desired amount of shade. You may find that covering a portion of the top and one side of your greenhouse will provide adequate protection. Shade materials will work up to 40 percent more effectively, if they are installed on the outside of your greenhouse.
In addition, check the amount of sunlight on your greenhouse when the sun is the strongest. You can arrange your plants so that ones that are more sensitive to sunlight are sheltered by more sun-loving varieties. Placing a small greenhouse near natural shade sources will eliminate the need for any extra shade materials.
Sunlight by plant type
Chrysanthemums and snapdragons like a large amount of sunlight. Lilies, begonias, and orchids prefer moderate sunlight. Ferns, dracaena and philodendron need more shade. If you are unsure of the correct amount of light, consult with a local nursery for the best advice.
Ventilation tips and advice
Without adequate ventilation, you could end up with too much humidity built up inside your greenhouse. Small greenhouses can be difficult to ventilate. You may need to open the cover for a few hours a day to allow air to circulate. Some models will have a roll-up cover over a screen material for appropriate airflow.
Large models should have vent openings. You may even choose to install a fan to pull fresh air through. If you install a fan, it should be placed high on one wall with one or more louvered vents low on the opposite wall.
Consider misting your plants on occasion, instead of just watering them. This will help maintain the humidity levels. When your greenhouse has the right balance of shade, humidity and ventilation, it will provide the best environment for your plant’s growth.