What to Look for in a Grow Light
by Admin
Posted on 03-10-2022 04:24 PM
Over the course of 2+ weeks, our testers used all different types of grow lights in their kitchens, bathrooms, greenhouses, and more.
They assessed each option on their ease of installation, clarity of instructions, effectiveness,
design
, brightness, and overall value. We combined these insights with our editors' and writers' independent research to bring you this list.
A grow light is an electric light to help plants grow. 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 (typically a varying combination of red and blue light, which generally appears pink to purple to the human eye). Outdoor conditions are mimicked with varying colour temperatures and spectral outputs from the grow light, as well as varying the intensity of the lamps. Depending on the type of plant being cultivated, the stage of cultivation (e.
The red/blue and migro (3500k) spectrum are best for balancing yield and short stem length green light and red light are closely matched for photosynthetic efficiency (within 5%) you need at least 12% blue light to prevent stretching as you increase blue light over 15% the stem length reduces but yield also reduces the experiments have shown that a mix of spectrum is best. From the mixed spectrum you can chose to target shorter plant height or higher growth rate. This can be a matter of preference as to what suits your situation. For example if you have a small space you may wish to sacrifice a little yield so that your plants stay short with dense growth.
Strength of light is typically measured in lux. Yellow light is more sensitive to the human eye, so the more yellow light, the more lux. However for plants this is almost the opposite. Plants are more sensitive to red and blue. Therefor, they can not be measured in lux. Light strength for plants is measured in ppfd, photosynthetic photon flux density. Or simply said, the density of the light flow that results in photosynthesis. Therefore the output of grow lights should be measured in ppfd, while lux only indicates the strength of the grow light to the human eye.
What is Grow Light Spectrum?
Light is obviously a critical component in growing plants, but it’s about quality as much as it is quantity.
Plants can only absorb and utilize certain spectrums of light. The spectrum of light that plants use is known as photosynthetically active radiation (par) and includes wavelengths from 400-700 nm. So, the light produced that doesn’t fall within this range cannot be absorbed by the plants and utilized for growth. Additionally, different wavelengths of light can trigger different responses in the plant. For example, red light is effective for increasing the total size of a plant, but when used alone can result in “stretched” plants that are tall with thin leaves.
Photosynthetically active radiation (par), designates the wavebands of solar radiation from 400 to 700 nanometers that photosynthetic organisms are able to use in the process of photosynthesis. All wavelengths between 400 and 700 nm contribute to the photosynthesis, in addition wavelengths carry information about the plant’s surroundings. Pbar there is critical information for plants beyond par area, in the uv range below 400 nm and in the far- red region above 700 nm. These areas and their relative ratios strongly affect plant growth. Hence, it is more accurate to refer to photobiologically active radiation 280-800 nm. R:fr (red : far red ratio) the r:fr ratio of a spectrum determines the ratio between active phytochromes (pfr) and inactive phytochromes (pr).