Greenhouses can help increase plant growth and fruit production and even allow you to plant crops that usually do not survive in your climate. Understanding how this process works can help you get the best from your greenhouse.
How Does a Green House Work?
The greenhouses provide light and heat
Plants need light, warm temperatures, air, water and nutrients to survive and grow; Different plants have different requirements for each of these needs. A greenhouse works by providing the first two requirements for your plants, but the last three are up to you.
Provide light
Greenhouses consist mainly of translucent materials, usually in the form of glass or transparent plastic. This gives indoor plants maximum access to sunlight, which they use for photosynthesis: combining carbon dioxide from the air and energy from sunlight to produce simple sugars, which the plant then uses as food. On average, plants need about six hours of sun per day, although this varies depending on the type of plant; By placing your greenhouse in a sunny place all day long, the plants inside will be adequately lit.
Provide heat
Greenhouses are warmer than the open spaces, because all the sunlight that passes through the walls of glass or clear plastic turns into heat when it hits a solid surface, such as soil or plants to inside the greenhouse. Light is really a form of energy, which is why plants can use it to fuel photosynthesis.
- >When light hits a solid surface, the surface absorbs some of that energy, which converts it into infrared energy (or heat): the darker the surface, the more energy it can absorb and turn into heat.
- >Infrared energy has a different "shape" of light energy - what scientists call the wavelength - so even though light can easily pass through the glass walls of a greenhouse, this heat takes longer to escape.
- >The trapped heat warms the air inside the greenhouse and, as a greenhouse is relatively airtight, the warmer air stays inside, increasing the temperature of the entire building. This is the same effect you have surely experienced when you get into a car that has been sitting in a sunny car park for a few hours.
With enough sun, the temperature inside a greenhouse can become much higher than the outside temperature. In fact, on a hot, sunny day, you may need to ventilate the greenhouse all day to prevent indoor cooking. On a cloudy day, less sun means the greenhouse will heat more slowly, if at all. For this reason, greenhouses are more useful in very sunny areas.
When there is no sun
The plastic or glass that makes up most of the outside of a greenhouse is ideal for letting in as much light as possible, but it's a bad insulator; Thermal energy travels but eventually escapes to the outside world. As long as the sun is shining, it does not matter, because light energy comes in faster than heat can get out of it. At night, however, all this thermal energy will leave quickly, leaving your plants at the mercy of lower night temperatures. In order to protect your tender plants, you must store excess heat during the day or use an artificial heat source during the night.
Thermal Mass
Different materials require different amounts of energy to heat, a characteristic known as thermal mass. The higher the material density, the more energy is needed to increase the material's temperature. Thus, high density materials such as stone, brick, concrete, and even water can store a lot of heat energy. Adding these ingredients to your greenhouse means that it will take longer for the building to heat up during the day because heat energy is trapped inside high density materials; However, at night, all that extra heat energy will slowly be released into the air in the greenhouse, keeping your plants warmer after sunset.
Some greenhouse owners are active in multi-tasking by storing large fish tanks inside their greenhouses: the water in the tank provides a lot of thermal mass to store heat, fish grow faster and more productively thanks to extra warmth, and the waste that is obtained during cleaning out the fish tank makes an excellent fertilizer for greenhouse plants.
Artificial Heat
If adding more thermal mass to a greenhouse is not an option, you can always use artificial heat sources such as space heaters. Ideally, you want a heat source that you can link to the thermostat so that it automatically keeps the temperature within the desired range. Greenhouse stores carry many types of artificial heaters specifically designed for use in greenhouses.
Meet the needs of your plants
Although greenhouses are very effective on both their strengths (light and heat), your plants will always need your help to meet their other needs. In fact, high levels of light and heat often cause plants to consume nutrients and carbon dioxide at an accelerated rate, which means you have to fertilize regularly and ventilate the greenhouse periodically to provide fresh air. High temperatures also make water evaporate faster. Diligent watering is therefore essential, especially for potted plants. Taking care of these simple tasks will help your greenhouse plants thrive.
