For plant growth and development, light waves in specific parts of the spectrum are required. In our color perception, this is light in the red and blue range.
The blue part of the spectrum has wavelengths of 420-460 nm and the red part has wavelengths of 630-670 nm. Plants need the rest of the plant growth spectrum, but in much lesser quantities.
Plants "light up" when planting seedlings and maintaining the greenhouse. They extend daylight hours with additional lighting. You can do this with ordinary lights, as their spectrum also contains the desired range of light radiation.
Plant grow lights differ from regular lights in that the plant grow light spectrum consists primarily of waves of the desired length. So in theory they will be more economical than regular backlights.
In fact, the plant's "unnecessary" spectrum consumes less energy. This light source is also called agricultural light. They sell not only individual bulbs, but also entire fixture. They are also known as plant grow lights or plant fill lights.
Special lamps for plant lighting can be of different types. The glow spectrum can't be simply changed here without a normal incandescent lamp.
High Pressure Sodium (HpS), Metal Halide (MGL), Mercury Discharge Lamp (DRL), Fluorescent Plant Grow Lights (with different connectors, including standard E27), LEDs (ribbon, lamps with different sockets).
1. High pressure sodium lamp
This plant light exists for a long time. It is also used in large greenhouses dedicated to growing vegetables, as well as in large greenhouses for seedlings. With basic sodium grow lights, light can travel in all directions.
For a greenhouse, this is acceptable. But it is inconvenient for the house because it blinds the eyes. Conventional sodium farm lamps can be installed in lighting fixtures with reflectors.
They produce roughly the same effect as a mirror coating. For small projects, boxes with reflective walls can be made. This reduces the cost of grow lights, but in small volumes, air temperature must be monitored. This type of light can get very hot.
2. Metal halide lamp (MHD) for plants
This is one of the subspecies of gas discharge lamps. It is characterized by the presence of halogen vapor in the bulb. The rest of the structure is very similar to other gas discharge lamps.
If we look at the spectrum emitted by this type of grow light, we will see clear pulse trains in the green and orange areas. There is less blue, but that's enough.
With an extended red spectrum, MGL lamps are suitable not only for the start of the growing season, but also for crop formation and maturity. So you can choose a spectrum for every type of plant, but the price of special lights is not satisfactory.
3. Mercury discharge lamp (DRL)
The special feature of such gas discharge lamps is that no additional equipment is required to use them. All you need to do is imply screw the grow light into a standard socket connected to a 220 V network.
The second point is that the bulbs are made with a mirror coating, which creates a directional flow of light without wasting energy on "lighting the ceiling". Gas discharge mercury grow lamps are called DRLFs. Radiation is more intense in the red and blue parts of the spectrum.
4. Fluorescent plant grow light
This is also a type of gas discharge lamp that can be used to grow seedlings with conventional fluorescent grow lights. But it is tall and skinny with underdeveloped root systems. Therefore, it is better to use special lamps. They are many times more expensive than conventional ones due to the more complex production process.
5. LED plant grow lights
Red and blue elements have been added to LED plant grow lights to some extent. The only problem is that they also cut for vegetation and flowering. For seedlings, they are ineffective because the root system is weak and the internodes are long. Therefore, for seedling growth, it is best to make your own lights or add blue.
In general, LED plant grow light is an economically correct solution. There are also opponents of LED plant grow light technology, but they have no clear arguments.