18 misunderstandings of LED plant growth lights
LED grow lights are becoming very popular, if you want to buy a new grow light system or upgrade an old fluorescent light fixture, they are a very good choice. This post about the myth of LED plant growth lights will save you time and money.
As with any new technology, there are many misunderstandings about LED plant growth lights. Some started because the public lacked knowledge, but many started by manufacturers trying to sell their products. Some of them prefer to keep us in the dark so they can make outrageous claims, but better companies will not. We need to do our part to become educated consumers, so that we can correctly evaluate the information disseminated and the product itself.
Before reading all of this article, don't buy LED grow lights.
Misunderstanding 1: Watt means brightness
For incandescent and fluorescent lamps, Watt is a good indicator of the brightness of the light. A 100-watt bulb is always brighter than a 60-watt bulb. This is not the case with LED grow lights. Lower wattage can produce more light.
The watt rating of an LED grow light will tell you how much electricity it will use and the ongoing cost of running the light, but it will hardly tell you the brightness of the light or whether the light is suitable for growing plants.
Misunderstanding 2: You can use a simple wattage per unit area rule
How many watts are needed per square foot of planting area? Consumers want to know, the manufacturer is willing to give you a rule, 15 watts per square foot of seedlings. You can find similar rules for other types of plants, but none of them makes much sense.
Watt is not equal to the amount of light. But the most important thing is that Watt cannot tell you the quality of light (that is, the wavelength of light). What you really want to know is the PPFD (photosynthetic photon flux density) at a given point under the led plant growth lamp.
As a general guide, you can use these values:
100-300 PPFD for seedlings
200-600 PPFD for vegetative growth
600-1,000 PPFD blossom
800-2,000 PPFD sunlight (depending on altitude, location, etc.)
600 – 1,600 PPFD full shading
More than 800 PPFD may damage the plants.
Misunderstanding 3: PAR is a measure of light intensity
You will find it difficult to find the PPFD value of most lamps. LED store lights will not provide this value because they are not sold specifically for plant growth. Many LED grow lights will not give you this value, because they want to sell to you in watts, but give you that value-don't buy from these companies.
Another reason you cannot find the value of PPFD is that many people equate PPFD with PAR. They provide PPFD values, but call them PAR values. They just don't understand what PAR means-it is a measure of light quality, not intensity.
If the product does not advertise the PPFD value, but does show you the PAR value-you can usually assume that they are the same thing. The unit should be μmol/m2/s.
Misunderstanding 4: PAR measures the needs of light plants
The term PAR (photosynthetically active radiation), when used correctly, describes the spectrum used by plants, which lies between 400 and 700 nm. Since plants use more blue and red light, these colors are more weighted than yellow and green.
PAR is a measure of light quality from the perspective of plants. It does not measure quantity.
PAR ignores the use of light plants below 400 nm and above 700 nm.
Misunderstanding 5: The efficiency of LED grow lights is 100%
A common misunderstanding of LED grow lights is that they convert electricity to light at 100% efficiency. They are more effective than older technologies such as incandescent and fluorescent lamps, but they are not 100% effective.
Misunderstanding 6: LED grow lights do not produce heat
In theory, LED grow lights can convert all electricity into light, but this is only suitable for storybooks. In real life, an LED converts 20% or more of electrical energy into heat.
A luminaire containing 100 individual LED bulbs generates a lot of heat. The design of the lamp makes most of the heat radiate from the back of the lamp, drawing it away from the plants. Larger units also contain fans that blow the heat away. This is all very important, because the heat will shorten the life of the LED bulb.
Misunderstanding 7: The higher the power, the better the bulb
LED bulb-a single unit that emits light and can provide various power ratings. 1, 3, 5, and 10 watt light bulbs are common. This leads to another myth. It is generally believed that a 3 watt device does not produce as much light as a 5 watt device-so a 5 watt device must be better. Things are not that simple.
Most light bulbs cannot operate at 100% efficiency. Higher wattage bulbs tend to operate at lower efficiency because they generate too much heat at higher efficiency. A 5-watt bulb may emit the same amount of light as a 3-watt bulb.
The wattage of the bulb will not tell you much.
Higher watt bulbs are newer technology and usually cost more. Their life span may also be shorter. Considering current technology, your best deal is a 3 watt bulb. This is a good compromise between efficiency, reliability and cost.
A new technology called COB LED (chip-on-board LED) will have high efficiency and a longer lifespan, but the price will be higher. I think this technology is too new and there are still problems. One potential benefit of this technology is that it allows manufacturers to create longer light tracks, similar to traditional 4-foot fluorescent lamps. In this configuration, it will cover a larger household area. Manufacturers have not yet taken advantage of this feature, probably because larger equipment is more expensive to transport, but there are some DIY systems that are worth studying.
Misunderstanding 8: imitating sunlight is the best
Plants evolve under sunlight, so we assume that sunlight is what plants want. Plants do not use most of the yellow and green light in sunlight.
Promote LED plant growth lights because it has the "same spectrum as the sun", which clearly shows that the company does not understand plant growth lights.
Misunderstanding 9: White light is better than Burple
is the industry name for the light produced by many LED grow lights. Since most of these lights contain a lot of LED plant growth lights, the result of blue and red bulbs is a burple.
We always grow plants under white light, and outside, they grow under yellow-white sunlight. It is natural to think that white light is more suitable for planting plants, but this is not the case.
The best light is the light of the relative amount of light wavelength needed to produce the plants. They use more blue and red, and less yellow and green. It does not have to look white.
Misunderstanding 10: Decrease in intensity according to the inverse square rule
As the light moves away from the light source, the light will spread out and the intensity of any given point will decrease. This follows the inverse square rule, that is, if the distance is doubled, the intensity will be reduced to 1/4. If you move the plant from 1 foot to 2 feet under the light, it will receive 1/4 of the light.
This rule applies to point light sources, but most LED plant growth lamps contain many LED bulbs, so they are not point light sources. Therefore, this rule does not apply to LED grow lights.
Another more complicated factor is that in the real world, this rule only applies to the light source directly below. When you move to both sides, the rule is also invalid.
Since it’s important to know how much light gets at any point under the luminaire, the manufacturer should provide you with this information
Misunderstanding 11: Coverage area specifications are true
What is the growth area under the LED plant growth light? This is the most important issue because it determines how many plants you can grow, and it varies from lamp to lamp.
The manufacturer tries to help you by providing a "coverage value", and say that the coverage area is 8 square feet, for example. This sounds great, but this number is absolutely meaningless. If you raise the light higher, it will cover more area, so unless they also provide light height and light intensity values for the entire area, the coverage area number has no value.
Let's take a closer look at this Ali. You are looking at the growth area from above the lamp. The numbers are the PPFD values at certain points under the lamp. The lamp is suspended 2 feet above the growth surface.
Please be sure to note that they refer to PAR values-but they are actually PPFD values in μmol/m2/s.
The specifications of this lamp suggest that the coverage area is "24" and the core coverage area is 4x3 feet". The reason why this area is longer than wider is because the shape of the light is rectangular. The above figure shows that the circle and square of the rectangular lamp are meaningless , But let us assume that the numbers are correct.
Directly under light, your PPFD value is 780, which is sufficient light for any plant to grow and bloom. Suppose you want to cover an area of 3 x 3 feet, and the PPFD of the light at the edge of the growth area is between 30 and 200. This is enough to plant seedlings, but nothing more.
Let us look at this from a different perspective. Suppose that after doing a lot of diligent research, you decide to provide a minimum PPFD of 300. This reduces the growth area under this light to an area of 2 x 2 feet, and the corners will only get about 200 PPFD. Therefore, for your requirement (ie 300 PPFD), your coverage area is 2 x 2 feet instead of Propaganda 4 x 3 feet.
Misunderstanding 12: PAR 20, PAR 30, etc.
This is not a real myth, but it does make things confusing. PAR 20 and PAR 30 are the lamp size names, in this case PAR stands for parabolic aluminized reflector. It describes the shape and size of the bulb and has nothing to do with the quality of the light. PAR 20 and PAR 30 are common sizes of light bulbs used in homes.
The confusion arises because these sizes are now made into household LED lights. These are not suitable for growing more than one plant.
Misunderstanding 13: Plants don’t use green light
The wavelength of light absorbed by plants is used for photosynthesis
The wavelength of light absorbed by plants is used for photosynthesis
Some factual information can easily lead to wrong conclusions. Plants look green because they reflect green light and absorb red and blue. This all makes sense, so if they reflect green light, they won't use it.
The absorption spectrum of the extracted chlorophyll is a peak that appears in the blue and red regions, but does not absorb green light. We again concluded that plants do not use green light in photosynthesis.
Some green light (about 500 nm) is absorbed by plants. When we observe the photosynthesis of the whole leaf instead of the extracted chlorophyll, it is clear that green light does help photosynthesis.
We now know that plants grow best under a broad spectrum that encompasses all wavelengths, including near-infrared and even near-ultraviolet. A good LED grow light will provide a wide spectrum, including some green light.
Misunderstanding 14: LED plant lights will not damage plants
LED grow lights tend to generate less heat than the old technology, and their light intensity is relatively low. The conclusion that can be drawn from this is that you can place plants as close to the light as possible without burning them.
The reality is that modern LED plant growth lights can produce very high light and can cause photobleaching and burn leaves. This is largely dependent on the plant, but 800 PPFD is enough to damage some plants.
Misunderstanding 15 Blue is a vegetable, red is a flower
Even if fluorescent technology is used, this is a myth, but it still exists in LED grow lights. People who use cool white (more blue light) bulbs used to add some incandescent bulbs (very red light) when plants are blooming. It is believed that red light is needed to initiate the flowering process.
Some early LED plant growth lights were red and blue. Blue lights are best for vegetables, and red lights are best for flowers. There are even lights that allow you to switch between vegetable mode (turn on more blue bulbs) and flower mode (turn on more red bulbs).
The reality is that plants always grow and bloom best under blue and red light. You may want to fine-tune it at different stages of the growth cycle, but for home use, we can ignore it.
Misunderstanding 16: The more lumens the better
Lumen is a measure of light intensity, so it is logical to think that a grow light with more lumens is better. The problem is that lumens are measured by the human eye. We see green and yellow light much better than red and blue light.
Taking into account this extreme situation, the light is only yellow. People see a lot of light, so it has a high lumen rating. But plants cannot make good use of yellow light, so for plants, the intensity of this light is very low.
Lumens are very suitable for evaluating the light intensity of your home, but they are almost useless for evaluating LED grow lights.
Misunderstanding 17: LED plant lights will not grow plants
Some early LED plant lights did not produce much light and were not suitable for planting, except for some very low light level requirements. All this has changed. The newer LED grow lights provide plenty of light for seedlings and low-grade plants such as lettuce and African violets.
You can purchase a complete system including a reflector, or you can purchase a 4-foot-long LED plant growth lamp to replace the traditional fluorescent bulb, so you can continue to use your existing lamps. Even better, the prices of these products have fallen.
Misunderstanding 18: Kelvin conversion from summer to winter is important
Fluorescent tubes and new LED grow lights use the Kelvin (K) scale to measure the color of light. Blue and white have a higher Kelvin value than red and white. Since Kelvin is a measure of temperature, these lamps are also called cold light and warm light.
The light in spring is bluer, and the light in autumn is redder. Some people think that it is a good idea to simulate this natural change by using a bluer light (6500 Kelvin) in the spring and a red light (3500 Kelvin) in the fall.
In the northern and southern hemispheres, the color does change, because winter sunlight must pass through more of the atmosphere, but the change from spring to autumn is only 300-500K. This is not enough to ensure that the lights change with the changing of the seasons.
In the world of LED grow lights, Kelvin is of little significance. It is much better to compare actual spectra, but they may be difficult to obtain.
