A greenhouse functions as a safe environment for plants to thrive year round. How well the plants grow indicates how well the greenhouse functions. Greenhouses must be monitored continuously and adjusted for changing environmental conditions. The most important factors influencing the function of a greenhouse include light, temperature and humidity.
Since plants depend on light for life, lighting is the most important consideration for greenhouses. According to West Virginia University, "the greenhouse should be located where it gets maximum sunlight. The first choice of location is the south or southeast side of a building or shade trees." Too much light is far better than too little light because blocking out light is easier and less expensive than providing additional light.
If greenhouse plants seem to be suffering from too much light, dim the area with shade cloth, blinds or greenhouse-industry shading paint. Plants suffering from too little light will require the addition of a grow light or removal of objects that are blocking light from the greenhouse. Another strategy for boosting light intensity in a greenhouse is by painting objects white so they reflect as much light as possible.
Temperature is the second most important factor affecting the function of a greenhouse. Monitoring the thermometer closely helps plants thrive. The weather is the greatest factor affecting temperature. If the weather is rainy, expect your greenhouse to be damper than normal. If the weather is hot and sunny, the greenhouse is also likely to be hot.
Greenhouses typically have either a natural (e.g., roof vents) or mechanical (e.g., fans) ventilation system to help with temperature control. Thermal screens install in the roof of a greenhouse to shade plants from hot sun. If the temperature is low outside, then anticipate your greenhouse being cooler than normal. Cold-climate greenhouses may require an additional heating system during the winter months.
According to Alabama Cooperative Extension, "relative humidity is a measure of how much water is dissolved in the air at a particular temperature expressed as a percentage." Plants accept a relatively wide range of humidity levels, preferring a range of 45% to 85%. Relative humidity levels below 45% can cause growth and water consumption issues.
High outside temperatures combined with excess ventilation cause low humidity levels in greenhouses. Spray a hose inside and keep the greenhouse fully stocked to effortlessly increase relative humidity. Relative humidity levels above 85% inside the greenhouse can lead to fungal problems. Decrease relative humidity levels in the greenhouse by increasing ventilation and reducing plant watering. Dose plants with an anti-fungal treatment if needed.