Light, a basic need
All gardeners know that light is a crucial element for the growth of their plants. Some, like cacti and succulents, require intense direct light, while others, like most tropical plants, prefer to avoid direct sunlight and thrive in indirect, moderate light. The effects of insufficient light are quite easily observed: etiolation, lackluster plants, loss of color, etc.
In this article, we will see why light is so important for our plants and also how we can provide them with artificial lighting if our light conditions are insufficient.
Photosynthesis
It would be difficult to understand the importance of light in depth without first going through some notions of plant biology.
We know that plants need light. But do we really know and understand why? In fact, by capturing light, plants actually produce their own fuel, their own food! The equation is quite simple: lack of light = lack of food.
Let's look at this in more detail, but simply.
Plants are made up of plant cells in which various organelles (components) are bathed in interaction with each other. Among these organelles: chloroplasts. Chloroplasts, due to their chlorophyll content, are responsible for the physiological process of photosynthesis by which plants use light energy and transform it into another energy, this time chemical. Indeed, with the process of photosynthesis, plants have the formidable capacity to take the energy given to them by light to transform water (H 2 O) and carbon dioxide (CO 2 ) (captured by the stomata of their leaves and by their roots) into sugars (carbohydrates) and oxygen (O 2 ).
The process of photosynthesis and cellular activity in plants could be explained in more detail, but for our purposes here we will limit ourselves to these explanations.
Let us add that photosynthesis takes place mainly in the leaves of plants which act as light sensors. The upper leaves, often more exposed to light, will have a higher photosynthetic activity than the lower leaves, often less exposed to light.
Factors that affect photosynthesis
Photosynthesis is therefore a process which regulates the internal activity of plants and on which both their growth and their needs depend.
Some external elements have a direct influence on the photosynthesis process, such as temperature, carbon dioxide content, water quantity and nutrients, some internal factors and illumination.
There is no perfect temperature that suits all plants. It all depends on their origins, but generally speaking, we can say that the colder it is, the more the physiological activities of the plant are slowed down, therefore the less photosynthesis there is. This is what happens, for example, when a state of dormancy is induced in certain plants. The opposite effect also exists: a warmer temperature (within the limits of what is possible for plants, do not try to put your plants in the oven!) will have the effect of increasing the internal activity of the plants.
Carbon dioxide content also affects photosynthesis. The more carbon dioxide there is in the ambient air, the more the photosynthesis process increases. Here too, there is a limit: when the plant is saturated, it closes its stomata and blocks the entry of carbon dioxide. The issue of carbon dioxide is of interest for growing areas where ventilation is less or not active. For example, greenhouse operators sometimes use carbon dioxide injectors in winter to meet the needs of their crops.
Water and nutrients (mineral salts) are essential for photosynthesis. A plant with a water deficit will close its stomata and no longer photosynthesize, to avoid the risk of dying from drying out. Regarding nutrients, to be able to produce chlorophyll and photosynthesize, a plant needs elements such as nitrogen (N), phosphorus (P), magnesium (Mg), chlorine (Cl), iron (Fe), manganese (Mn), boron (B), and zinc (Zn). A deficiency of any of these elements will affect the entire process.
The other factor that greatly affects the photosynthesis process, and not the least, is illumination . Illumination consists of both the quality of light and its quantity , and it is when both are combined that a plant can have efficient photosynthesis. Photosynthesis increases with illumination up to a saturation point (maximum photosynthesis) and it decreases sharply when the light decreases. There is a critical stage of illumination, however, under which the plant will remain in the vegetative state, without showing any activity if the illumination does not increase.
If this is you, if you love plants, but you don't have enough natural light in your home to keep them beautiful. Whether they're wilting, not growing, experiencing so much stress that they end up with pests, or dying... Well, it's time to see what artificial lighting can do for you.
What do we know about light?
When shopping for artificial lighting for our plants, we need to have some basic knowledge. We often see grow lights that emit a purple light while others often emit a white light... Which one should we choose? How do we know what's right for our plants?
Let's look at some concepts to better understand the rest of the article.
Light is made of photons (particles) that move in waves (wave motions). Each wavelength corresponds to a color of light (red has a fairly long wavelength (700 nm), while violet has a shorter wavelength (400 nm).
White light is actually made up of a set of colors (therefore a set of waves of different lengths), as can be seen when, for example, light is passed through a crystal prism (or a rainbow is observed).
Not all white light is created equal, as it does not contain the same proportions of each color. There are warm whites (which contain more yellow, orange, and red) and cool whites (which contain more violet, green, and blue). The color of light is measured in degrees Kelvin: 1,000K represents a very warm white, 10,000K a very cool white. The light of a bright, cloudless sun is 6,500K.
The color or wavelength of light corresponds to what is called light quality, which we discussed above. This little detour is to explain that the plant reacts differently depending on the wavelength (or color of light) it receives. For example, blue-violet light is absorbed by chlorophyll during the plant's growth phase, it promotes more robust plants, with a bushy habit, increases metabolism, growth and development. Red light, on the other hand, is absorbed more during the flowering phase. It will tend to influence the smell and flavor of plants by increasing their concentration of oils and sugars. It is also red light that influences the photoperiod (the plant knows that it is day when it receives daylight and knows that it is night when it does not), which is useful for certain types of flowering crops. And it can sometimes promote etiolation, which is not what we want, however.
Remember that the sun itself presents the full spectrum of light colors. We may wonder if lamps that provide only purple light meet all of plants' needs.
The other aspect of illumination, the quantity of light , is also very important. Even the best quality light, if not present in sufficient quantity, will not meet the needs of our plants. Generally speaking, the more light plants receive, the more their metabolism activates, and the more they grow. To this equation, we must naturally add water, relative humidity, nutrients and the right temperature.
The unit of measurement for illuminance is the lux * (international system). To give you an idea, a sunny summer day provides more than 50,000 lux of illuminance, while a well-lit room in a house ranges from 100 to 500 lux. The interior of a house with a window in full sunlight, this time, provides about 60,000 lux, while a cloudy day provides 2,000 lux. Moreover, the further you are from the light source, the more the amount of light received decreases. This goes without saying, you might think, but what's surprising is that if there is, say, twice as much distance, there will be four times less light! It drops quickly.
It is estimated that full sun plants (cacti and succulents for example) need 20,000 to 30,000 lux to be able to photosynthesize efficiently, while shade plants (certain tropical plants such as Calathea or Sansevieria ) can make do with 2,000 to 5,000 lux.
Add to this the fact that modern house windows are made up of more layers than ever before, and they often block out certain types of rays. It is not uncommon to have plants in a window that are well exposed, but which never seem to be satisfied, and which continue to grow proudly (wither). It is difficult to give them more without resorting to artificial lighting.
* On the packaging of lighting products, we will often see the unit of measurement for illuminance in lumens. The difference is that lux corresponds to the quantity of light received while lumen corresponds to the quantity of light diffused. To have an equivalence, it is necessary to consider that 1 lux = 1 lumen / m 2 .
Artificial lighting
To optimize the growth of our plants indoors using artificial lighting, we must try to provide them with lighting that is as close as possible to sunlight, powerful (lux) and balanced (in terms of the color spectrum).
In some cases, the choice of lighting will depend on what we want to do with our plants. If we want to induce flowering in a certain type of crop, for example, we will choose lamps that diffuse more red light. And if we want to keep them in the vegetative stage, we will go for a light that diffuses more blue-violet.
It goes without saying that the duration of lighting has a strong impact on the results we want to achieve. It is difficult to give a precise number of hours, because everything actually depends on the needs of the plant in question. For example, if we want to induce flowering in a type of crop, or to start seedlings, we can light up to 16 hours / day! But as a general rule, we are not going too far wrong by providing a dozen hours of lighting / day to our plants and giving them a rest period at night. Because, yes, they need it too.
That said, in most cases, gardeners want their plants to have good overall growth and be healthy. And to meet these needs, the ideal would be to look for a light that replicates the sun's spectrum as closely as possible.
Incandescent bulbs
Let's not beat around the bush: this type of lighting is poor quality for your plants. Avoid it.
Compact fluorescent light bulbs (CFL)
This type of bulb is definitely better than an incandescent bulb for your plants' needs. It's a type of lighting that can be useful, for example, for seedlings and seedlings.
The spectrum of this type of bulb is usually either warm white or cool white, but the model offered by the company SunBlaster (which offers several good quality horticultural accessories (including heat mats and thermostats ), is 6400K, which mimics sunlight. Sunblaster's compact fluorescent bulbs also come in 2700K, for gardeners who are more interested in inducing flowering. These bulbs are suitable for propagation and growth and are compatible with all standard sockets. They are available at 26 watts, which is equivalent to a 100-watt incandescent bulb. They provide 1700 lumens.
T5 fluorescent tubes
T5 horticultural fluorescent tubes (not the T12 fluorescent tubes in your office) generally provide a good spectrum (good quality of light) and are particularly useful for seedlings and seedlings. However, the lux level is generally low. Depending on the fluorescent tube model you choose, they can sometimes be bulky and fragile.
That said, the SunBlaster company has models of T5 fluorescent tubes with integrated reflectors that are already mounted on the ballasts and that you simply have to plug in. These fluorescent tubes are equipped with reflectors that allow better diffusion of light and offer a full spectrum of light ( Full Spectrum ), which mimics sunlight quite well. They are available in different sizes (12 in / 690 lumens, 18 in / 1120 lumens, 24 in / 1500 lumens, 36 in / 2450 lumens, 48 in / 3730 lumens) so that they can fit into most gardening spaces.
The T5H0 also exists without a reflector , but the advantage of the reflector is to spread the light more widely over the canopy of the plant, penetrating deeper into the foliage of the plant, without consuming additional energy.
They call it the T5HO Nanotech Combo , which includes: the electronic ballast, a 6400K fluorescent, a 6' power cord with on/off switch, a 14" connecting cord, clips for hanging the ballast or securing it to a flat surface.
T5HO 6400K lamps have a spectral distribution with peak intensity between 435 nm and 615 nm, wavelengths suitable for photosynthesis. These lamps are ideal for propagation and long-term growth.
The company also offers replacement lamps , so there is no need to buy the complete kit once equipped.
These lamps emit little heat, which is interesting compared to some previously offered models. The luminaires can therefore be placed 6 to 8 inches above the plant canopy, thus maximizing photosynthetic response and growth.
Horticultural LED lamp
LED horticultural lamps are currently the best options on the market, in terms of lighting quality and energy savings. They produce less heat than fluorescent tubes, but more light, and the light they emit is continuous, which is not the case with many standard horticultural lamps, which emit intermittently, although this is invisible to the naked eye. The fact that the light is continuous brings them even closer to sunlight and makes them more efficient than other lights.
The Sunblast company offers a truly high-performance product with its LED lighting.
There is the LED Sunblaster Self Cooling , which comes in different sizes (12 in, 18 in, 24 in, 36 in, 48 in) and whose main attraction is that it does not emit any unwanted heat.
And there's the Sunblaster Prismatic lens LED , available in the same sizes (12" / 1600 lumens, 18" / 2500 lumens, 24" / 3400 lumens, 36" / 5000 lumens, 48" / 6700 lumens) (offers more than double the lumens of the T5HO), with the same appeal, but with a prismatic lens. This improvement causes the light to pass through a prism that refracts and reflects the light in a 90-degree beam angle rather than 120 degrees, like the older models. This ensures more light reaches the plant canopy and significantly reduces losses. These LED light strips have a full spectrum with a maximum of 6400K, which is suitable for all horticultural uses: seeds, general cultivation, propagation, micro greens production, etc. In terms of wavelengths, this is probably the type of lamp that currently provides the broadest spectrum (between 400 nm and 700 nm). The improved light output of this model of horticultural lamp stimulates faster growth.
The Sunblaster Prismatic lens LED is also sold in kits: the electronic ballast, a 6400K fluorescent, a 6 ft power cord with on/off switch, a 14 in connecting cord, clips for hanging the ballast or fixing it to a flat surface.
Accessories offered by Sunblaster
The Sunblaster company offers several accessories and thus meets various needs that one might have when installing their different lamps, whether to suspend them or to assemble the ballasts together, which is quite interesting when one has a long surface to illuminate:
Extension connectors for T5HO and LED ballasts :
Suspension clips with rings for T5HO and LED :
Suspension clips for T5HO and LED :
Connections for T5HO and LED :
So we can see that just because we don't have natural light in our homes or because we don't have enough lighting doesn't mean we should deprive ourselves of having plants. There are a multitude of solutions to fill the lack of lighting, for different types of spaces, for different budgets. You just need to understand how lighting works to be able to choose what best suits our needs and those of our plants!
