{Disarmed} Growing a plant with artificial light is possible if you know how: the mega-guide to LED lighting for indoor plants

Maybe you like plants and have thought about setting up a small indoor garden or a crop in some area of ​​your house. Have you discarded the idea because you have little natural light in that room? Well, reconsider, because today it is possible knowing which light is the best to grow your plants and make them look healthy.

If these summer days are hot, you drink more water, look for the shade or take a dip, right? You have ways of avoiding or coping as well as possible in a situation that, if it lasts too long, could be dangerous. Well, plants are unable to flee from threats or to seek the best environmental conditions. However, they have internal mechanisms that allow them to perceive any stimulus and be able to generate a response. And in addition, they have an impressive adaptability. That is why they are on continuous alert detecting any change that happens around. They perceive temperature, position with respect to other plants and other physical and chemical parameters.

If we take into account that their way of obtaining food is through light through photosynthesis, it is easy to assume that this will be one of the most developed 'senses', since only in relation to light, they are capable of determine the type, orientation, intensity, duration and closeness of other individuals through the shadow they receive. All this information will determine their shape and growth rate, including the time it takes to produce flowers and fruits.

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In nature they are already looking for life and are used to receiving direct sunlight, but if we want a vertical garden, a micro-garden or plants in different rooms of the house and we have a bathroom without natural light, a dark living room or a hall in twilight, we have a little problem. No matter how indoor these plants are, they require light and, if we do not have it, we must provide it by giving them quality light that is as close to what they would receive under natural conditions . If we are going to talk about light, it is important that we address certain parameters.

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Light energy and plant pigments

Light is a type of electromagnetic radiation and, as such, travels in waves , just like radio waves, microwaves, or X-rays. In waves, the distance from the crest (the highest part) of one wave to the next it is known as wavelength and it will be characteristic of each type of radiation. The unit of measurement is the nanometer (nm), one millionth of a meter. Radiation with long wavelengths, such as radio waves or microwaves, have less energy (note in the following image that the distance between ridges is greater), unlike those more dangerous radiation such as X or gamma rays where the longitude wave is short and therefore transmit much more energy.

Within this electromagnetic spectrum, our eyes only cover what appears as visible light, which ranges from 400 to 700 nm. Although the light with which we see appears white to us, it actually has all the "colors" of light, that is, all the wavelengths within visible light (the rainbow is an example).

The plants are going to go a little bit beyond our sight. They will be able to perceive wavelengths greater than 700 nm, already entering the infrared and less than 400 nm, going to the area of ​​ultraviolet radiation, although the really important area is between 400 and 700 nm and that is where the energy used by the plant for photosynthesis, called photosynthetically active radiation (PAR).

And how do they perceive it if they don't have eyes? We have rods and cones in the retina that are responsible for our vision, but in the case of plants, they are specialized molecules called pigments . There are different types of pigments and they will perceive a specific wavelength of light. In addition to chlorophyll, which is the best known (and most abundant) responsible for the green color of plants, we will find cryptochromes and phytochromes, among others. For example, uv-B light receptors (280-320 nm); cryptochromes, which mainly absorb UV-A light (320-390 nm) and blue (400-500 nm); chlorophylls, which absorb blue and red light (600-700 nm); carotenoids, which absorb green and yellow light (400-600 nm), and phytochromes, which absorb red and far red light (700-800 nm).

Although plants perceive light below 400 nm and above 700 nm, the really important area for generating the energy they need for photosynthesis is in that wavelength range.

What should the light of our plants have?

To know the best light we can provide our plants we need to take into account the three factors that most affect their growth :

Light quality

With quality we refer to the color or the sum of colors that make up the light that reaches the plant. All wavelengths within their absorption spectrum are important for plants, but they prefer blue and red , basically because depending on the stage of their life they are in, it helps them to develop or provides information. extra that can be very valuable, as with red and far red. Green, let's not forget, is not absorbed by plants but reflected, and that is why we see them in that color.

• Blue. Between 400-500 nm. It is the color that favors vegetative growth, that is, from when the seedling germinates until it blooms. If we only provide this color, the plant will have a short stature and a darker green.

• Red / Far Red. Between 600-700 nm. This relationship affects the length of the stem and favors flowering. The red / far red ratio informs them if they have other plants too close and therefore they may be taking light away, activating in this case the protocol of escaping from the shade. A greater amount of far red (that is, lower red / far red ratio), as is the case with incandescent bulbs, favors more length between leaves on the same stem, resulting in a taller plant. Therefore, the best option is a combination of blue and red light since this ratio is the one that is most beneficial for plant growth.

Light duration

Too much light can be as damaging to plants as a prolonged absence. We also know this parameter as the photoperiod , that is, the number of hours of light followed throughout 24 hours. Over the course of the year, the number of hours of daylight varies, right? We have more hours of daylight in spring and summer and less in fall and winter. Plants are adapted to this in nature, but even so, there are plants that prefer to bloom in the short day time (8 hours of light and 16 hours of darkness), others that will be long days (16 hours of light and 8 of darkness) and others, of neutral day; It will not give them exactly the same because the flowering will not depend on the hours of light and darkness but will be induced by other factors.

Obviously, the needs will change depending on the flowers or crops that we want to grow, since their requirements will be different, but, in any case, they all need a break and rest for a while in the dark. For example, as long-day crops we have summer flowers and some vegetables, such as onion, lettuce, spinach and potatoes. Indoor plants are usually short-day (remember that they do not need as much light as if they were outdoors). As for neutral day we have tomatoes, cucumbers and some strawberries. Once the number of hours of light and darkness has been established, it is best to couple the artificial light with a timer that turns the light on and off automatically.

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Light intensity

The most critical time for plant growth is at the beginning, when it begins to germinate. It is the phase in which they need the greatest amount of light , like a baby that requires the greatest care. Keep this in mind if you are putting up seedlings and you are going to set up your small garden from scratch.

When they are small, it is advisable to put the artificial light bulb (if they do not have enough natural light) at about 5-7 cm high and raise it as they grow so that they are always about 8-10 cm from the light source. In indoor plants with flowers that are already adult, 25-30 cm high is fine and if they are plants grown for their foliage, we can put it at 90 cm.

So what light do I put on my plants?

Once we are clear about the quality, duration and intensity of the light that our plants need indoors, the key question comes: what light to put on the plants? In the following figure we are going to see some sources of artificial light. Look at the first diagram that represents natural sunlight. That is the ideal for plants and the one that we must try to reproduce.

Remember that within the useful area of ​​the spectrum, red and blue light (or better yet, the combination of both) is the most important.

Incandescent lamps

Incandescent lamps emit light with a continuous spectrum (that's a good thing) although it is poor in blues and rich in reds . Even so, in the absence of natural light they can provide quantity and quality of light. They have been widely used until now due to their low price, broad spectrum emission, variety of forms, use in direct and alternating current, different voltages, etc.

On the contrary, they are highly polluting systems, with low luminous efficiency (only 10-15% of the energy consumed by the lamp is transformed into the form of light and the rest is heat) and a short useful life (500-1000 h) , reasons why, the tendency is for them to disappear. In fact, the European Union and some countries have banned the manufacture and sale of low energy efficiency incandescent lamps, with the aim of increasing energy efficiency and therefore saving energy.

Halogen lamps

Incandescent lamps were perfected and gave rise to halogen lamps, based on the same principle, but with better light and color performance, although they did reach such a high temperature that it was difficult not to get burned if they were handled on. For practically the same reasons as the previous ones, the EU began to withdraw them in 2009 and in 2018 the manufacture and import of halogens for most uses ended.

High intensity discharge (HID) lamps

High intensity discharge (HID) lamps are used to supplement light during the day or replace this part of the night . HIDs include high-pressure mercury, high- and low-pressure sodium lamps, and metal halide lamps. High pressure sodium vapor is still widely used in public lighting today (those orange bulbs in street lamps, roads, tunnels ... for example).

These lamps have a completely different operation than incandescent ones. They stand out for their great economy in operation, thanks to the fact that they generate an extremely high luminous flux in a very small space, they emit almost no heat, excellent color rendering and long life are other advantages of high-pressure discharge lamps. its compact construction, which facilitates the orientation of the light.

The spectrum of light they emit is not continuous, unlike incandescent and halogen, but it does present important peaks in blue and red that ensure a balanced growth of our plants. On the contrary, they are very dangerous lamps due to the type of waste they generate and the possibility of poisoning (specifically with mercury and metal halide lamps).

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Fluorescent lamps

Moving forward in energy efficiency and safety (well, this is relative), we come across fluorescent lamps. They are low pressure mercury vapor discharge lamps. Inside the tube we will find a small amount of mercury vapor and an inert gas, usually neon or argon. The tungsten filament at the end of the tube is what manages to ionize the gases inside.

Fluorescents are very suitable for growth, for shoots and for rooting cuttings, so they are especially recommended during the early stages of plant growth . Among their advantages, we highlight that they are quite inexpensive, have a high luminous performance and useful life (5000 - 75,000 hours), in addition to a wide variety of color tones that, because they are diffuse, mean visual comfort and do not emit too much color. However, they take up more space, they present a flickering that can be somewhat annoying (and that is corrected with an electronic ballast), their ignition time is appreciable and, in addition, multiple switching on and off can reduce their useful life (also corrected by the use of the ballast). It should be noted that due to the presence of mercury vapor they are considered hazardous waste and there is a possibility of poisoning by this vapor.

Standard fluorescent bulbs may not be the most suitable for lighting the home, but they are great for supplementing natural light for indoor plants or for starter seedlings . Their cooler light makes them one-dimensional, so they're ideal when the target is lush foliage, not flowers. Since this light does not damage the leaves of the plants by not emitting too much heat, they can be placed low.

But within the fluorescent lamps we also find them compact or low consumption that have the following advantages over the previous ones: obviously their low consumption, high light output, little heat emission, they are small, they have spectral quality and long life. Despite being somewhat more expensive, their longevity and energy efficiency make them considered an option to consider since they pay off in the long term.

Compact Full Spectrum Fluorescent Lights (CFLs) are the best choice as they provide a balance between warm and cool light (red and blue) that faithfully reproduces natural light. Available in tube and bulb form, CFL grow lights are more intense than standard fluorescent lights.

Latest generation: LEDs

Finally, the LED lights (Light Emitting Diode) seem to have come to stay and unseat all the previous ones over time. Its use began as discreet for signaling, stair markings or level changes, but a series of attractive characteristics and the undoubted advantages they present, have made its development and implementation for multiple applications unstoppable.

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Due to their variety, they allow us to choose the color of the emitted light since they offer light of different wavelengths . We find a variety of shapes (ceiling, spotlights, tubes ...) that are easy to handle since, as they do not contain toxic compounds, they do not generate health or environmental problems, making them the most ecological option. In addition, they represent great energy savings thanks to low consumption, high luminosity and hardness, low maintenance and long life.

In the scientific literature we can find numerous works on the use of LEDs in the cultivation of plants, where they are used as a single source of lighting or as a lighting supplement. As we already know by now, the energy zone used by plants is between 400 and 700 nm, regions where pigments use that absorbed energy to carry out their fundamental processes.

The combination of red and blue light from LEDs allows good growth and development of plants since it is found in the most important regions, although it is true that monochromatic red light at 680 nm seems to be 36% more efficient for photosynthesis than monochromatic blue at 460 nm.

Looking at the artificial light spectra figure above, it seems logical to combine a cool white (blue) LED with a warm white (red) LED to provide all the spectrum needed . In this way, we can achieve "isolated" colors from a light source since we provide the blue light and the red light that the plant needs without providing anything more than what is necessary for growth and flowering. With this we could save on energy costs, because why illuminate with others such as green if the plant does not absorb it.

Combining a cool white (blue) LED with a warm white (red) LED provides the full spectrum needed

Having a vertical garden at home or a small indoor cultivation has become a fashion in recent times, so manufacturers have put the batteries and today we have LED 'grow' that combine blue light in a single source and red. Voilà. They are narrow spectrum LED grow lights and should not be confused with regular LEDs. They provide a purplish-looking light as they contain blue and red light bulbs.

If you like to light up your living room or bathroom in purple like a pub, go ahead. But if we want the same effect on plants and a 'normal' light we would have to use broad spectrum 'grow' LEDs. That is, we will see it white (like natural visible light) and it will provide the entire spectrum useful for the plant including blue and red, of course.

What you have to look at if you want plants with artificial light

We have a good variety of increasingly efficient and respectful artificial lights on the market, although it is clear that LED lights are gaining ground because their qualities are unbeatable and provide quality light for the growth of your plants. The important thing before deciding on type or another is that you take into account:

1. Will they be in an area with little natural light or nothing reaches them?
2. What plants do you want to grow / enjoy at home? Remember that the photoperiod may be different.
3. You must use the appropriate light for the specific growth phase (germination, vegetative growth, flowering)

Once we have this clear, there are all kinds of forms of light sources: attached to flexible arms such as flexo or fixed, such as floor lamps or hanging from the ceiling, but, in any case, it is advisable to couple them with timers and remote controls to program the ignition. already paid. Plants like us need a few hours of rest.

If after reading the entire article you are not at all clear, go to the simple: blue light (cold) for germination and growth and warm light (red) for flower production . Or better yet, a broad spectrum and voila. In your trusted store they will be happy to help you.

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The news Growing a plant with artificial light is possible if you know how: the mega-guide to LED lighting for indoor plants was originally published in xiaomist.com by Bioamara .