what to buy for a grow light and what not to buy
LED Grow Lights are becoming very pop and they are a skilful choice if you are ownership a new grow light system or upgrading your old florescent fixture. This post about LED grow lite myths will save you time and money.
Equally with whatever new technology there are many myths about LED grow lights. Some are started because of a lack of knowledge by the general public, but many are started by manufacturers who are trying to sell their product. Some of them prefer to keep us in the dark and so they can make outrageous claims, just the better companies don't practise this. We demand to do our part and become educated consumers and so that we can properly evaluate both the bulletin being circulate and the product itself.
Don't go shopping for LED grow lights until y'all read all of this postal service.
LED grow light myths, showing a cerise and blue LED
Myth #i: Watts Indicate Brightness
With incandescent and florescent lights, watts were a practiced mensurate of the brightness of a light. A 100 watt bulb was always brighter than a 60 watt bulb. Not so with LED. Lower wattage can produce more light.
The watts rating on a LED grow low-cal tells you lot how much electricity it will use, and therefore the ongoing cost to run the light, but it tells you lot very little about how bright the calorie-free is, or how suitable the low-cal is for growing plants.
Myth #two: You lot Can Use a Simple Watts Per Area Rule
How many watts do you need per foursquare foot of growing area? Consumers want to know, and manufacturers are quite willing to requite you a rule such equally, seedlings demand fifteen watts per sq foot. You can observe like rules for other types of plants, simply none of them mean very much.
As explained above, watts do not equate to the amount of lite. Simply even more of import, watts tell you nothing near the quality of light (i.e. the wavelengths of low-cal). What you actually want to know is the PPFD (photosynthetic photon flux density) for a given spot nether the grow light.
As a full general guide you lot can utilise these values:
- 100-300 PPFD for seedlings
- 200-600 PPFD for vegetative growth
- 600-1,000 PPFD for flowering
- 800-2,000 PPFD for sunlight (depends on elevation, location etc)
- 600 – i,600 PPFD for full shade
Plants can be damaged with more than 800 PPFD.
Myth #three: PAR is a Measure of Light Intensity
Y'all volition have trouble finding a PPFD value for virtually lights. LED shop lights will non provide this value because they are not being sold specifically for plant growth. Many LED grow lights will non give yous this value considering they want to sell you on watts and give you that value instead – don't buy from these companies.
The other reason you volition have trouble finding a PPFD value is that many people equate PPFD to PAR. They provide PPFD values but call them PAR values. They just don't understand what PAR means – information technology is a measure of low-cal quality, not intensity.
If the product does non advertise a PPFD value, simply does prove you a PAR value – you lot can unremarkably assume they are the aforementioned thing. The units should be μmol/m2/due south.
Myth #4: PAR Measures The Calorie-free Plants Need
The term PAR (Photosynthetically Active Radiation), when properly used, describes the light spectra that plants use, between 400 and 700 nm. Since plants use more than blue and ruddy calorie-free these colors get weighted higher than yellowish and green.
PAR is a way to measure the quality of light from the plants perspective. It does not measure quantity.
PAR ignores the light plants use beneath 400 nm and higher up 700 nm.
Myth #5: LEDs Are 100% Efficient
A mutual misconception of LED lights is that they are 100% efficient at turning electricity into light. Granted they are more efficient than older technology like incandescent and florescent lights, but they are not 100% efficient.
Myth #6: LEDs Don't Produce Heat
In theory LED lights could convert all of the electricity into light, but that but works in story books. In real life, an LED converts 20% or more of the electricity into heat.
A light fixture containing 100 private LED bulbs creates a lot of heat. The lights are designed so that nearly of this heat comes out the back of the fixture, directing it abroad from the plant. Larger units also contain fans that blow the heat away. This is important since estrus shortens the life of LED bulbs.
Myth #7: Higher Watt Bulbs are Better
LED bulbs – the single units that give off the low-cal, are bachelor in diverse watt ratings. ane, 3, five, x watt bulbs are common. This leads to another myth. It is mutual to run across the claim that a 3 watt unit of measurement does not produce every bit much light equally a five watt unit of measurement – so the 5 must exist ameliorate. Information technology is not that elementary.
Virtually bulbs are non run at 100% efficiency. College wattage bulbs tend to be run at lower efficiency levels since they produce too much heat at higher efficiency. So a 5 watt seedling may exist giving the aforementioned amount of lite as a iii watt bulb.
The wattage of the bulb does not tell you lot very much.
Higher watt bulbs are newer technology and generally cost more than. They may also have a shorter life. Given the electric current applied science, your best bang for the buck is a 3 watt bulb. Information technology is a proficient compromise between efficiency, reliability and toll.
A newer engineering science called COB LED (chip-on-board LED), is more than efficient, has a longer life, merely is more than expensive. At the moment, I think the technology is too new and however has issues. One potential benefit of this technology is that it allows the industry to make longer light tracks, similar to a traditional 4 ft florescent fixture. In that configuration it would encompass a larger area for dwelling house use. Manufacturers have not taken advantage of this feature, maybe because of college shipping costs for a larger unit, just at that place are some DIY systems worth looking into, such as the one pictured here, created by Ichabod Crane on International Canagraphic Mag.
Myth #8: Mimicking Sunlight is Best
Plants have evolved nether the lord's day, so we assume sunlight is what plants want. It is not. Much of the yellowish and greenish lite in sunlight is not used by plants.
Promoting a light for plant growth because it has the "same light spectra as the sun" clearly shows that the company does not understand grow lights.
Myth #9: White Light is Improve Than Burple
"Burple" is the industry name for the low-cal produced by many LED grow lights. Since nigh of these lights incorporate a lot 
of blue and cerise bulbs the upshot is a burple.
Traditionally we take e'er grown plants under white light, and exterior they grow under sunlight which is a yellow-white. Information technology is natural to think white light is better for growing plants – its not.
The best light is one that produces the wavelengths of light that plants need in the relative amounts plants want. They employ more bluish and red, and less xanthous and green. It does non have to look white.
Myth #10: Intensity Drops by the Inverse Square Rule
Every bit light moves away from the source, the light spreads out, and the intensity at whatever given signal is reduced. This follows the inverse foursquare dominion, whereby if the distance doubles, the intensity is reduced to 1/iv. If yous move a plant from 1 ft under the calorie-free to 2 ft, it will receive i/four as much low-cal.
This rule works for bespeak sources of light, but most LED fixtures contain many LED bulbs, and then they are not a betoken source of light. Therefore the rule does not apply to LED lights.
The other complication is that in the real world the rule simply works well right below the light source. As y'all motion out to the sides, the dominion is likewise not valid.
Since it is important to know how much light you go at any point under the fixture, the manufacturer should provide you with that information, every bit seen in the diagram below
Myth #11: Coverage Expanse Specifications Are Truthful
What is the growing area under an LED low-cal? This is an of import question since it determines how many plants you can grow and it varies from lamp to lamp.
Manufacturers effort to assistance you past providing a "coverage area value" and say something similar, the coverage area is 8 sq feet. That sounds great, but this number means absolutely nothing. If you heighten a calorie-free upward higher it will cover more than area, so unless they besides provide the summit of the light and the low-cal intensity values across that whole area, the coverage area number is of no value.
Lets take a close wait at this. The diagram beneath shows the coverage area for a Viparspectra Par 700 light. You are viewing the growing area from to a higher place the calorie-free and the numbers are the PPFD values at certain points under the calorie-free, with the light hanging at 2 anxiety higher up the growing surface.
notation that they refer to PAR values – but they are actually PPFD values in μmol/m2/south.
The specifications for this light suggest a coverage area of "Core Coverage at 24″ Meridian is 4x3ft". The reason why this area is longer than broad is considering the shape of the light is a rectangle. Information technology makes no sense that the higher up diagram shows circles and squares for a rectangular light, but lets assume the numbers are correct.
Directly under the low-cal you lot accept a PPFD value of 780, which is lots of light to abound and flower any plant. Presume you want to cover a 3 x iii ft area, the light at the edges of this growing expanse have a PPFD of between thirty and 200. That is enough for growing seedlings, merely non much more.
Lets await at this from a unlike perspective. Lets say that afterward doing a lot of diligent enquiry you decide that you want to provide a minimum PPFD of 300. That reduces the growing area under this calorie-free to a ii x2 ft area, and even and so the corners will but be getting about 200 PPFD. And so for your requirements (ie 300 PPFD), your coverage area is 2 x 2 ft, non the advertised 4 10 three ft.
Without seeing this light distribution diagram and knowing the top used to measure the values, the coverage area in the specifications is of piffling aid. At least Viparspectra provides this information; many manufacturers don't. If they don't, don't purchase from them.
Myth #12: PAR 20, PAR 30, etc.
This i is not really a myth, simply information technology does confuse things. PAR 20 and PAR 30 are lamp size designations and PAR in this example stands for parabolic aluminized reflector. It describes the shape and size of the seedling and has nothing to do with the quality of the light. PAR 20 and PAR 30 are common sizes for bulbs used in the home.
The confusion arises because these sizes are at present fabricated every bit LED lights for the home. These are not suitable for growing more than than a single plant.
Myth #thirteen: Plants Don't Use Light-green Light
Light wavelengths captivated by plants for photosynthesis
A bit of factual information can hands lead to incorrect conclusions. Plants look dark-green considering they reflect green light and absorb red an blue. That makes sense and it follows that if they reflect greenish lite, they don't use it.
The absorption spectra for extracted chlorophyll shows peaks in the bluish and cerise zones, but no absorption of green light. Again we conclude plants don't use green light in photosynthesis.
We are wrong. Some greenish lite (around 500 nm) is absorbed by plants, and when we expect at photosynthesis in a whole leaf instead of extracted chlorophyll, information technology is clear that dark-green light does contribute to photosynthesis.
Nosotros now know that plants grow all-time with a broad spectrum that contains all wavelengths including virtually IR and maybe even near UV. A good LED grow low-cal will provide a wide spectrum which includes some green calorie-free.
Myth #14: LED Lights Can't Damage Plants
LED lights tend to produce less oestrus than older technology, and their low-cal intensity is relatively low. This has lead to the determination that you lot can put plants equally shut to the lights equally you want and you won't burn them.
The reality is that modern LED grow lights tin produce a very high level of light and it can cause photograph-bleaching and burn leaves. This depends very much on the plant, only a PPFD of 800 is enough to impairment some plants.
Myth #15 Blue is For Veg, Red is For Flower
This was a myth even with florescent technology merely information technology persists with LED. People using absurd white (more blue light) bulbs used to add a few incandescent bulbs (very red light) when it was time for plants to blossom. It was believed that reddish light was needed to initiate the flowering process.
Some of the early LED lights were red and blue and it naturally followed that the bluish ones would be best for veg and the blood-red for flowers. There are even lights that permit yous to switch between a veg way ( more blue bulbs on) and a bloom fashion (more red bulbs on).
The reality is that plants grow and flower best with both blue and ruddy low-cal all of the time. For production you lot might desire to fine tune this at unlike stages in a growth cycle, but for home use we can ignore it.
Myth #16: The More Lumens, the Better
Lumens is a measure out of light intensity and so it logical to think that a grow light with more lumens is ameliorate. The trouble is that lumens measure intensity based on the human eye, and we run across green and yellowish light much better than reddish and blue.
Consider this extreme case where the light is simply yellow. People see a lot of light and therefore it gets a high lumen rating. Just plants don't use yellow low-cal very well, and so for a establish this light has a very low intensity.
Lumens work not bad for evaluating the intensity of lights for you dwelling, simply its mostly useless for evaluating LED grow lights.
Myth #17: LED Shop Lights Won't Grow Plants
Some of the early on LED shop lights did not produce much light and were non suitable for growing plants, except for some very low light level requirements. That has all changed. The newer LED shop lights provide lots of low-cal for seedlings and low level plants like lettuce and African violets.
You can buy complete systems including the reflectors or you lot can purchase 4 ft long LED tubes that supercede traditional florescent bulbs, allowing you to go along using the existing fixtures. Even better is that the toll of these has come way down.
Myth #18: Summer-to-Winter Kelvin Shift is Important
Florescent tubes and the new LED shop lights measure out the color of lite using a Kelvin (Grand) scale. A blueish-white has a higher Kelvin value than a red-white. Since Kelvin is a unit of measurement of measure out for temperature these lights are also chosen absurd and warm.
Lite in spring is more blue, and autumn light is more scarlet. Some people believe that it is a good thought to mimic this natural shift by using bluer light (6500 Kelvin) in spring and a redder calorie-free (3500 Kelvin) in fall.
In northern and southern hemispheres at that place is a real shift in color because lord's day low-cal has to travel through more atmosphere in winter, only the change from spring to fall is merely 300-500K. That is non significant enough to warrant changing lights with the seasons.
In the world of LED grow lights, Kelvin means very picayune. It is much ameliorate to compare actual spectra, but they can exist hard to come by. Some manufacturer practise show them on their website.
References:
- Photo Source; Tyler Nienhouse
Source: https://www.gardenmyths.com/18-led-grow-light-myths/
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