A greenhouse is a transparent structure in which people grow plants that require special conditions. Sunlight gets through, but the plants are protected from the cold, wind, heavy rain, and animals such as birds that might undermine their growth.
Some people use the terms hothouse or glasshouse with the same meaning as greenhouse. They vary in size from small structures people have in their gardens to giant industrial-sized buildings.
When the sun is shining, the interior of a greenhouse is significantly warmer than the ambient temperature outside.
Greenhouse LED lighting
Many structures today are equipped with greenhouse LED lighting. When there isn’t enough natural light, such as during the night or an extremely cloudy day, the artificial lights are switched on, which increases the yield of several types of crops.
We refer to artificial light sources as grow lights or plant lights. They are designed to stimulate growth. In countries that are far from the equator, grow lights are common in greenhouses. In the winter months, there is much less natural light than during the summer.
According to Wikipedia:
“Grow lights either attempt to provide a light spectrum similar to that of the sun, or to provide a spectrum that is more tailored to the needs of the plants being cultivated.”
“Outdoor conditions are mimicked with varying color, temperatures and spectral outputs from the grow light, as well as varying the intensity of the lamps.”
Short history of greenhouses
Growing plants and cultivating crops in environmentally controlled spaces has existed since Ancient Roman times. Tiberius, the second Roman emperor, who ruled from 14 AD to 37 AD, consumed cucumbers every day throughout the year.
Tiberius’ gardeners planted cucumbers in wheeled carts which they pulled outdoors during the day. When the Sun went down, they brought the carts back into warm rooms. The vegetables were under a transparent cloth-like material.
In the 1450s, during the Joseon dynasty of Korea, there were heated greenhouses. It wasn’t until the 17th century that greenhouses as we know them today appeared. They first appeared in the Netherlands and then the United Kingdom.
In the Netherlands today, there are many of the world’s largest greenhouses, which produce millions of tons of vegetables annually.
Variable spectrum LEDs more efficient than white LEDs
According to California Lightworks, which makes LED grow lights:
“Variable spectrum LED grow lights are always more efficient than white LEDs. While both lights provide the energy-saving benefits that have come to famously characterize all LED lighting, white LEDs waste too high a percentage of their energy on the green light spectrum.”
Plants absorb red and blue light for photosynthesis and reflect much of the green light. Accessory pigments which exist within plants, such as carotenes and xanthophylls, absorb some of the green light.
With variable spectrum LED lights, much less green light is wasted.
California Lightworks adds:
“If you want control over your yields, chemical profile, flavor, and overall quality, variable spectrum LED lights have far more to offer.”