What kind of auxiliary lighting is needed to grow plants indoors or in the garden?

Posted on Sep 01 , 2020

Plants need good lighting, as well as ordinary indoor flowers and seedlings growing on windowsills. Properly designed auxiliary lighting will provide photosynthesis for them at any time of the year to ensure their normal growth and development, including the root system. If there is not enough light in the house to illuminate the flowers, their development will stop immediately and their appearance will deteriorate greatly.


On the contrary, additional lighting that is too bright will burn the leaves, which will cause plant loss or even death. This is why you will not mistake the choice for the right lamp. The modern lighting market provides users with a large number of models, which are suitable for lighting greenhouses and greenhouses, as well as illuminating windowsills and shelves with seedlings. Our theme is which auxiliary lighting is most suitable for lighting plants in the home.


First, let us understand the auxiliary light sources on the market:


The auxiliary light source has certain physical characteristics. The most important thing for us is color temperature, spectrum and brightness.


What is color temperature is well known to camera owners. The so-called "white balance" is set on it. Generally, the lower the temperature, the more orange-red tones in the light. The higher-the blue the bluer. The color temperature determines how the human eye perceives natural light. The closer it is to 4200K (the color temperature of the sun), the whiter the light. Another feature is that the color rendering index is a reflection of the appearance of natural objects under this lamp. Generally, the closer the color temperature of the lamp is to 4200K, the better the color rendering, but please remember that two lamps with the same color temperature may have different color rendering.

The closer the color rendering index is to 100%, the closer the light is to the sunlight of the eyes. The spectrum is the quantitative ratio of different wavelengths in light. The wavelength determines its color. Violet is the shortest, its length starts from 400nm, red is the longest, the longest is 700nm. Ultraviolet rays are shorter than 400nm, and infrared rays are shorter than 700nm.


Plants may not be able to perceive waves in the entire spectral range well. The best perception is in the red and ultraviolet blue parts of the spectrum. The worst is-green and yellow. For the eyes, the color of the lamp is the average value of the spectrum. Therefore, two lamps with the same color temperature may have different spectra, and therefore, the appearance of colors is also different.


If it is difficult to provide enough light, the spectrum is an important feature. Therefore, when lighting with a special lamp (fluorescent lamp, flora glo) with an improved modified spectrum, the best results are only shown when there is a lack of lighting.


Under strong light conditions, the spectral composition of light will also affect the regulation of the growth process. To be sure, the more blue components in the spectrum, the less "stretching" the plant. This is why sodium lamps are often used in combination with metal halide lamps. The former emits a lot of red light, while the latter emits blue components to regulate the growth process.


Ultraviolet light plays a special role in the life of many plants, but this is beyond the scope of this article.


The luminosity is the same as the amount of light emitted by the lamp. It is often confused with lighting. Therefore, these two characteristics depend on each other, but the illuminance is the amount of light from the lamp to the surface, and the brightness is the amount of light emitted by the lamp. Agree, it's not exactly the same. Luminosity is measured in lumens. In order not to disturb your use of the formula (you can find and view it if you like), please consider that for fluorescent lamps without a reflector, the illuminance at 10 cm from the lamp is equal to the luminosity, and the illuminance at the point (sodium, mercury and energy-saving fluorescent lamps) is equal to 50 cm The surface illuminance of a point light source is proportional to the square of the distance. For tubular parts, the same but not so fast.


What are the commonly used auxiliary lights?

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The lights have the following types:


  • Incandescent lamp

  • halogen

  • Luminous (tube, compact, energy-saving)

  • Metal halide (MG) or metal halide

  • High-pressure sodium (the most common type is HPS)

  • HG


Incandescent or halogen lamps are not suitable for target auxiliary lighting of plants. They are too uneconomical and emit a lot of heat, so they will be much brighter than light when dried. We will not consider them.


fluorescent lamp


There are several types, but because the bulb temperature is low, they are all combined. Any fluorescent lamp needs a special starting device (ballast or ballast). It can be "electronic" or "throttle valve". The starting device is either built into the lamp (energy saving) or located in a special lamp. It is simply impossible to connect these lights (like all subsequent lights) to the socket. An electronic starter is usually better because it does not generate heat, emits no noise, and does not send high-frequency signals to the lamp (the lamp does not flicker), but it is much more expensive and often fails.


The capacity of the standard luminous tube is 20 (18) 30 (24) 40 (36) watts (imported analogues in parentheses), and the length is 60, 90 and 120 cm respectively. The efficiency of these lamps is considered a reference for comparison. It is three to five times that of an incandescent lamp. Energy-efficient and compact-these are the same fluorescent lamps, but with different characteristics. The unique feature of energy-saving batteries is that they are screwed into ordinary cartridges (they have a built-in starter).


When choosing a fluorescent lamp, it is important to consider the ratio (price per unit of power)/(working time). It is the best choice for imported similar products of large pipes and compact (very small pipes). The strange thing is that for energy-saving inverters, the ratio is very poor, because they have built-in control devices and are therefore costly.


Fluorescent lamps have a variety of spectra and color temperatures. Among them are special plants (flowers). However, their cost is several times the standard cost. The benefit (if any) can be felt only in low light conditions (why do we need it?) and obviously not much more. Therefore, I do not recommend that you buy and buy ads. With the same money, it is best to buy four ordinary lamps or one energy-saving lamp without lamps. The color temperature in the household classification is warm white (2700K, LTB), white (3500K, LB) and daytime (6000K, LD). The white bulb looks best. The fluorescent tube emits a cold "hospital" light. Imported lights are marked with different codes for each company, so it is best to ask the seller.


The purpose of the fluorescent lamp is to illuminate the plant shelf, and the flowers on the window sill are auxiliary lighting. It is necessary to fully grow plants that have special requirements for the light of fluorescent lamps (Hibiscus, Cactus, Giant Panda, etc.). Luminous lights are also used when illuminating botanical gardens and small flower cabinets.


Mercury, metal halide and sodium lamps are high-pressure gas discharge lamps. Their purpose is to create a lot of light. Therefore, they are very suitable for lighting greenhouses, winter gardens, large single plants and plants with particularly high lighting requirements.


All high-voltage lamps require special wiring diagrams, including the ignition element of the high-voltage lamps (voltage up to 10 kV), and the internal bulb temperature of the lamp reaches 1500 degrees, so special precautions need to be taken when using them. It is recommended to use all these lights only on protective glass, high-quality components and qualified circuit components, otherwise they are not safe to use in the home (light explosion or short circuit will cause fire). It should be noted that under the premise of observing all safety rules, good assembly and components, the burning hazard of these lights is no less than that of computers, and they can be safely left unattended.


Therefore, only special ignition devices (the same for all types of lamps) can use high-pressure lamps. The lamp itself is most often used in combination with a spotlight, which provides directional light and can be equipped with protective glass (to prevent lamp explosion and ultraviolet radiation). Many types of floodlights are equipped with a built-in ignition device, which is very convenient. It is important to remember the correspondence between the power of the ignition system and the power of the lamp.


Like fluorescent lamps, ballasts are chokes or electronic ballasts. The latter is very rare and is mainly found in imported floodlights.


The gas discharge lamp will not immediately emit light at full power, but will emit light when it is warmed up. Moreover, the extinguished heat lamp cannot be lit until it has cooled down. This problem is solved by using "heat shock" circuits and lights. If you don't use this IZU ("lighter", that is, a device that generates a powerful initial pulse to start the light), it may quickly fail.


Mercury lamp


The cheapest type of high-pressure lamp. A spectrum with a significant blue shift produces a lot of ultraviolet light. Their cheapness is compensated by their low light output, short service life and poor spectral characteristics, so it is not recommended to use them at home and we will not consider them in the future. This type of special lamp (Floraset) is screwed into the traditional lamp holder, with low luminous efficiency and poor price/quality ratio, but it is easy to use and can be used as a substitute for energy-saving fluorescent lamps.


Metal halide (MG)


This type of lamp should not be confused with halogen lamps. They are completely different in working characteristics and working principles. The MG lamp is the same as the mercury lamp, but the rare earth ions are introduced into the bulb, which greatly extends the service life and improves the light output and spectrum. Standard power (such as sodium) is 70, 150, 250 and 400 watts. Seventy watts have twice the service life, so it is not suitable for use.


Generally, the light output of MH lamps is equal to that of fluorescent lamps (per watt). The difference is that the light is not scattered but direct.


MG lamps come in many shapes-from frosted balls for standard threads to double-headed tubes for compact spotlights. I recommend using the latter because they have good characteristics and take up much less space.


All of these lamps can emit good white light at different color temperatures (standard 3200, 4200 or 5000). When the color temperature of this lamp is 4200, its color rendering index is close to 100%. Any objects and plants below them look absolutely natural, which is good news. The spectral composition is balanced and has blue and red regions.

The only disadvantage of these lights is the price. Compared with sodium salts, they are very expensive.


sodium lamp


In most cases, they are represented by so-called HPS lamps. Ideal optical power/price ratio, but there are notable exceptions. This light is orange-yellow. It's like a street lamp. The color rendering index tends to zero, and the spectrum is dominated by red rays. Therefore, these lamps are designed for use in industrial greenhouses or non-residential areas, such as balconies and greenhouses. The bright orange light annoys many people, but plants can grow well. In order to prevent plants from stretching or having a chance to appreciate plants normally, a combination of sodium lamp and MG is often used. When one visits the garden, one can temporarily turn off the sodium salt and enjoy the correct flowers under MG.


This is what I want to say to these lights. Please note that in my house, only two 150-watt floodlights with metal halide lamps illuminate the colonies. It is impossible to achieve this effect with fluorescent lights (more than 30,000 lux is enough to grow pandas or cacti). Therefore, if you follow safety precautions carefully, do not underestimate their benefits.


Knowing so many auxiliary lighting fixtures, I think you also have a preliminary understanding of lighting fixtures. It is recommended that you choose the light source based on the spectrum and characteristics required by the plant itself, such as the light source required for different stages such as germination and growth.

I hope this article can help you choose suitable auxiliary lighting, thank you for watching!

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