If you want to pre-grow your plants or then let them continue to grow and bloom in environment of your home, garage or hall, you should be clear that the plants have different needs. At least as far as light is concerned.
Sunlight is the most promising and, of course, the cheapest source of radiation in terms of its color spectrum. It is definitely possible to simulate this lighting nowadays, you just need to look for the right lighting sources that have the necessary properties.
But it's not just about mixing the different types of lighting we come across while walking through Baumax, where the salesman is as well informed as the director of a prosperous company about the movements of toilet paper - he wants more information.
Plants respond differently to different color spectra. Again, we get to the point where we try to simulate the outdoor environment as much as possible. In spring, sunlight is "brighter" than in autumn - this natural behavior, the different color spectrum of light (chromaticity temperature) is expressed in Kelvin (K). It actually determines the color of the light.
For germination and cloning of plants, ie the beginning of plant life, it is recommended to use lighting with a chromaticity temperature of 9000–11000 K (cool white). The color temperature of this light guarantees us a higher percentage of rooted cuttings, or a more compact beginning of growth in seedlings.
In the phase when the plants are older, but still in the growth phase, it is recommended to use lighting with a chromaticity temperature of 5600–6500 K (blue). When using this lighting, the plants will be more compact, the internode (mezzanine) will be shorter and the whole structure of the plant will be better formed. If, after the growing season, the light is replaced by so-called flowers, the plants will not stretch so much in height and will be more of a "more compact" appearance. It is recommended to use lighting with such a color temperature until the 1st week of flowering - this should ensure that the plants do not grow after switching the light period from growth (18 hours light / 6 hours dark) to flowering (12 hours light / 12 hours dark).
Once we want to achieve a quality inflorescence, it is again the best way to replace the light source with one that has a chromaticity temperature of 2000-3000 K (red). This will provide us with a better structure and number of flowers.
The color coding (white-blue-red) is divided according to the wavelengths in which the light reaches and is expressed in nanometers (nm).
You don't have to be a trained physicist and you definitely don't have to remember these data by heart, you usually just ask the salesman in a specialized garden center or grow shop for growth or flower lighting, or lighting for seedlings, and I believe that together you will find the necessary alternative.
Another important quantity according to which we choose lighting is the luminous flux, expressed in lumens (lm). Luminous flux does not have to depend on the power of light, which is expressed in watts (W) - as an example we could mention the difference between a 150W compact fluorescent lamp (CFL) and a 150W sodium lamp (HPS). Both of these light sources have the same power, but the sodium lamp will emit a much higher luminous flux than CFL. We will list more specific cases when we get to the various types of lighting. In general, the rule applies to luminous flux - the larger, the better.
As already mentioned, another important (but not always decisive) variable is performance. As for sodium and metal halide lamps, which are currently the most used variant of lighting for plants, it is also possible to deduce from this quantity how large an area they can effectively illuminate (but of course it also depends on the distance of the light source from the tops of plants).
A characteristic feature of plant lighting is its photosynthetically Active Radiation (FAR). If we do not go into biophysical details, it can be said that it is the light to which the plants respond and which is necessary for the proper course of photosynthesis. It can be defined as light whose wavelength ranges from 400 to 700 nm, or as the intensity of the current of photons (elementary particles of electromagnetic energy) that impinges on the surface of the leaf and is received by the leaf. It is precisely the light energy that is needed (in combination with other elements of photosynthesis such as temperature, CO2 and water) for the process of converting energy into simple sugars and oxygen - the basic chain for life on earth.