Why Grow Lights?
To grow marijuana indoors above all you need marijuana grow lights. Your grow light is going to be your key piece of equipment. At the end, you will understand why we recommend LED Grow Lights for DIY beginners.
Why? Because indoors your marijuana plants won’t have access to the sun. DUHHHH. So you have to replace it somehow. This guide will explain everything you need to know about doing exactly that with marijuana grow lights.
The sun tells plants how and when to grow. It also literally feeds them through photosynthesis. Growing indoors, you have to provide that information and nutrition artificially.
Your key job, then, as an indoor grower is to replace and mimic the sun.
Fortunately, all manner of different grow lights are available for indoor growing to achieve exactly that. We review many of the best ones in this article, which we update frequently. With the entry of Chinese manufacturers, the cost has come down even as quality and improvements have continued to climb. Here is the table of recommendations from that article, in case you just want to cut to the chase.
But not all plants need the same light. So marijuana grow lights are calibrated to the specific needs of marijuana plants.
Marijuana is light hungry. It needs powerful lights. Moreover, different strains of marijuana have different light requirements. So before buying marijuana grow lights, you have to do your research.
Spoiled For Choice…
Unfortunately, for beginners, the whole area of grow lighting can be highly confusing. Not only are there many different types, brands and models of grow lights available, there’s also no shortage of advice—what’s worse, some of it conflicting.
So in this beginners’ guide we’re going to run through the three main types of marijuana grow lights (fluorescent, HID or HPS, and LED) and their respective pros and cons. (In case it wasn’t already obvious, we are fans of LED Grow Lights, for reasons we explain below.)
We’ll explain how plants use and respond to light. We’ll also show you what you need to know and look out for when buying a marijuana grow light. We will answer the question about what is the best grow light (hint: LED Grow Lights.) And finally we’ll point you in the direction of the best options for a beginner.
Types of Marijuana Grow Lights
Fluorescent Grow Lights
Fluorescent grow lights are available in all sorts of shapes and sizes. From fluorescent tubes (T5s) to twisty CFL bulbs.
CFL Grow Lights
CFL stands for Compact Fluorescent Lighting.
As the name suggests, CFL grow lights can be great for growing in small spaces. The bulbs are relatively cool and the light less intense than some other grow lights, so they can hang quite close to the plants. Even very close, CFLs won’t overheat them or give them “light burn”.
CFL bulbs are also cheap and easily available. They’ll fit all kinds of different light fixtures. And they’re pretty cheap in terms of electricity used too.
- 26-watt/6400k bulb is equivalent to a 130-watt incandescent bulb
- Compact fluorescentspiral bulbs reduce energy costs
- UL Listed
- Fits any standard light fixture with Medium Base
- Produces 1600 lumens and will last an average of 10,000 hours
You can also find CFLs in various different color temperatures. The warmer, more red bulbs are better for the flowering stage. While “daylight” bulbs are bluer and better for the vegetative stage.
If you only want to grow one plant, you have a tiny space for growing, or you fancy trying out growing with a minimum level of investment, CFLs can be a great way to go.
Also, consider them for “stealth growing”, where you’re looking to grow as unobtrusively as possible. Being able to have small bulbs close to your plants is a great advantage for these kind of grows.
In fact, because fluorescent lights aren’t as intense as other marijuana grow lights, they actually need to be positioned close. Fluorescent light doesn’t penetrate as far down.
So if you’re using CFLs for your grow space, you need to have a number of bulbs, positioned closely and strategically, to make sure your whole plant is getting plenty of light from them.
Pros of CFL Marijuana Grow Lights
- Widely available.
- You can hang them close to plants.
- Good for small or short grow spaces.
- Low heat.
- Bulbs are relatively cheap.
- Bulbs fit in all kinds of light fixtures.
- Good for clones, seedlings and young plants (you would have to hang warmer, brighter marijuana grow lights further away to give the same light as close CFLs, thus wasting a lot of electricity).
- Cheap option for a first trial grow.
- Good for a single plant grow.
- Can be useful supplementing other more powerful lights.
- Not much extra ventilation needed.
Cons of CFL Marijuana Grow Lights
- Not good for large grows (if you want to harvest more than a few ounces, for instance).
- Relatively low yield per watt, if used for whole grow cycle.
- Need to check on your plants and light placement daily.
- You’ll have to learn how to train your plants to keep them growing low and flat (because fluorescent light doesn’t penetrate far).
- Not as energy efficient as some other marijuana grow lights.
- Not as long lasting as LEDs.
- Other marijuana grow lights give better control of color spectrum emitted.
- Other lights are brighter, more powerful.
- Many other lights more easily and accurately mimic sunlight.
Fluorescent Tubes aka T5 Grow Lights
T5 grow lights (the T stands for tube, the 5 = ⅝-inch diameter) are easily available in garden and home improvement or DIY stores. In fact, you can use them to grow all kinds of different plants.
These are a much bulkier option than CFLs. But given their size, better for larger grows.
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You’ll usually find them in longer, wider panels of multiple tubes. Like their smaller CFL counterparts, though, they run pretty cool, so you can still hang them quite close to your plants without harming them. And indeed they should be hung close—usually within about 4 inches.
While fluorescent light is predominantly blue, you can get T5s in different color temperatures to optimize your setup for different stages of marijuana growth.
Pros of T5 Marijuana Grow Lights
In addition to the pros for CFLs:
- Can cover a larger grow space and grow more plants
- Easier to use than similar sized HPS or HID marijuana grow lights
Cons of T5 Marijuana Grow Lights
In addition to the cons for CFLs:
- Less flexibility over fixtures than CFLs.
- Need to add extra “bloom” lights with a redder output for the flowering stage, to supplement the main cool blue tubes.
- Still need to train plants, to allow for the closer proximity and lower penetration of T5 lights.
- With larger lights and larger grow space, the watts soon start to add up. You’ll find fluorescent lights are at their most efficient and cost effective for smaller grows.
HID and CMH and LEC and Other Beasts
High Intensity Discharge (HID) marijuana grow lights are more efficient than fluorescent lights, but also run much hotter. They are still (probably) the most common grow lighting used for cannabis in older large grow operations, but newer operators (even big ones) are recognizing that LED Grow Lights have significant advantages in efficiency and cost.
HIDs are usually large oddly shaped bulbs that come in one of two varieties, Metal Halide (MH) and High Pressure Sodium (HPS). You’ll also see ceramic metal halide and Light Emitting Ceramics (LEC) bulbs, which are two names for the same thing, a bulb that’s a sort of mix of MH and HPS technology.
More specifically, LEC (aka CMH) bulbs are a type of MH bulb that use ceramics as a part of the bulb, just as HPS bulbs do. But let’s go back a bit and explain the differences between MH and HPS.
Differences Between MH and HPS Bulbs
Metal halide bulbs emit a bluish light and are often used for the vegetative stage of growing. HPS grow lights, on the other hand, are often added during flowering, as they give a yellower light that encourages bud production and are even more efficient than MH lights.
However, most weed growers who use these light use a combination of the two.
According to some, an HID setup gets better yield per watt than any other kind of grow light. However, others would argue that good LEDs used correctly are on a par.
All these kinds of bulb (HPS, MH, LEC) are HID bulbs. High Intensity Discharge. In other words, HOT.
As the name suggests, the light they discharge is of a much higher intensity than fluorescent grow lights. However, there are trade offs. Not just the heat and the extra cooling required to deal with it, but also the extra parts you’ll need compared to LEDs or fluorescents. In particular, the ballast (the gizmo that controls the current) is notoriously fickle in many lights, and usually expensive to replace.
More components = more things to wear out, go wrong or be mismatched.
Pros of HID Marijuana Grow Lights
- Some claim that HPS lights used in the flowering stage are the most efficient marijuana grow lights available in terms of yield per watt.
- HPS lights are excellent for flowering, and very efficient.
- Simple to use, no guesswork when trying to hang them at the right distance from the plant.
- Relatively low initial cost.
- Have been used effectively by growers for many years, so plenty of advice available.
- This also means the HID lights are more standardized than the newer LED grow light technology.
Cons of HID Marijuana Grow Lights
- Run very hot, requiring extra cooling and exhaust:
- More parts to go wrong.
- Have to set up exhaust and ducting.
- Extra cost of running the exhaust and cooling system (think “Air Conditioner.”)
- Bulbs give off less light over time, progressively deteriorating, so need to be replaced or placed lower than newer bulbs:
- You’ll need to replace MH bulbs about once a year (assuming 2-3 grows).
- HPS bulbs last around 2 years (4-5 grows).
- Relatively short lifespan of bulbs.
- More parts in general required, compared to other lighting types: external ballast (to mediate electrical current), extra cable, reflector or hood that houses the bulbs, all in addition to the aforementioned cooling and exhaust.
- Ballast can need replacing too, after around 20,000 hours of use.
- Have to hang this kind of marijuana grow lights high above plants, so need a tall grow space.
- Relatively high power requirements and running costs—especially compared to LEDs.
LED Marijuana Grow Lights
LED (Light Emitting Diode) is the newest marijuana grow light technology on the block, relatively speaking. These days it’s firmly established as one of the most credible options around though—and still constantly improving. And because it is based on chip technology (where do chips come from kiddies?–Yes, CHINA), LED grow lights are getting cheaper and better faster and faster.
Rather than using bulbs, arrangements of diodes or chips create the light. These chips are extremely bright and can penetrate further than other marijuana grow lights to easily nourish the whole plant.
Usually they produce the full spectrum of light needed by plants, meaning you can use them for the entire grow cycle of your marijuana plants. See this article that explains what “full spectrum” really means. Which along with the ease and simplicity of setting them up makes them an excellent choice for inexperienced weed growers.
While LEDs do run colder than other marijuana grow lights, put a lot of LEDs close together and they’ll still need some cooling. However, most growers won’t need any air conditioning to deal with this small amount of heat, unlike HID bulbs which can generate enough heat to require A/C.
Some LED grow lights are cleverly designed (“heat sink”) to dissipate heat without extra assistance and many others have fans built in to direct any heat away from plants.
LED grow lights are arguably the simplest and most versatile lights to grow with, but there are so many models available now from so many different manufacturers that it can be difficult to choose. Later in this article we’ll give you some tips to help you find the one that’s right for you. And of course, you can check our current review.
Pros of LED Marijuana Grow Lights
- Most energy efficient type of marijuana grow lights available—more brightness per watt consumed.
- LED light can penetrate further than other marijuana grow lights, to more easily reach and nourish the lower parts of your plants.
- Run much cooler than other lighting, so:
- Lower cooling costs.
- Less risk of heat damage to your plants.
- Lower running costs, as use far fewer watts compared to equivalent brightness HID lights.
- Long lifespan—LEDs can last 50,000 to 100,000 hours.
- No extra parts required, just plug in the light and hang it up straight out of the box.
- Very easy to set up.
- Waste no energy producing light in wavelengths that the plant can’t use.
- Some growers believe LEDs produce more potent and resinous buds, particularly grow lights with UV-B light as part of their spectrum.
- You can usually use one light for the whole grow, altering its height for different grow stages (many also have different settings for flowering and veg).
- Can also be very effective when used to supplement HID lighting.
- Usually quieter than HID setups, due to fewer and smaller fans running and little need for extra ventilation.
Cons of LED Marijuana Grow Lights
- High cost up front.
- Little industry standardization, meaning it can be hard to compare lights and ensure you’re getting a good one (see below for tips!).
- Larger LED grow lights will still need some cooling.
- It can take some experience and experimentation before you get as high or higher yield per watt as you can get with HID lights.
- You still need a fairly tall grow space. Many LED grow lights recommend hanging at 24” until being lowered for flowering.
- Because LEDs are so bright, you need to be careful not to hang them too close to the plants—even a light hungry plant like cannabis can have too much light.
PLEASE NOTE: Because LED marijuana grow lights are so simple to set up and use, can often be used for an entire grow cycle and work out cheaper in the long term with little or no loss of quality (arguably they can even raise bud quality and yield), we’re going to focus the rest of this beginners’ guide on LED grow lights.
In short, they’re an excellent option for anybody, but for the beginner in particular LED grow lights are the most flexible and most forgiving option.
And not only are they great for your first growing efforts, they’ll still be valuable to you later. Indeed, with extra experience you’ll get even better results from them. So you’re not going to outgrow them.
How Plants Use and Respond To Light
Cast your mind back to high school science classes and you’ll probably remember a little something about photosynthesis, the process by which plants turn light into fuel for growing.
But not only do plants feed on light they also respond to it in different ways. And react differently to the different colors or wavelengths of light present within sunlight.
Lumens are for Humans
First things first, the colors of light that are visible to us don’t 100% correspond with the spectrum of light that plants use and respond to.
So when you see the lumens boasted by marijuana grow lights, this measurement really only tells you how bright the light will appear to a human. What’s important to a plant is PAR, Photosynthetically Active Radiation—the wavelengths of light that a plant can use for photosynthesis.
PAR is the wavelengths between 400 and 700 nanometers.
The intensity of this light is measured in μmol/m2/s (micromoles per second per square meter) which is essentially the quantity of usable light falling onto a square meter of the plant per second. For a light hungry crop like cannabis, the more the better (up to about 800 μmol/m2/s, above which you risk damaging the plant).
However, while plants don’t use light outside this range to photosynthesize, they do respond to it. As such, you can use those wavelengths to train your plants and cause them to react in beneficial ways.
For this reason you will find that most LED marijuana grow lights offer ultraviolet and infrared in their full spectrum offerings, in addition to the wavelengths within the PAR range.
Ultraviolet
Ultraviolet is harmful both to humans and to plants. However, plants are able to protect themselves to some extent by producing what amounts to their own sunscreen. In cannabis plants this “sunscreen” is in fact THC-rich resin.
Which is why manufacturers often include UV-B in the spectrum produced by their marijuana grow lights.
A little UV-B exposure not only increases potency but the extra resin also helps protect the plants from pests and diseases.
Infrared
The ratio of infrared light to other red light gives clues to plants about how they should grow. A bit more infrared than normal, for instance, and the plant will think it is overshadowed and needs to grow taller to get more light.
Infrared light is also helpful for the light schedules you set to simulate day and night and the changing of the seasons.
Long days (18 hours) give your marijuana plants the illusion of summer. Switching to shorter days (12 hours) causes the plant to believe winter is coming and that it’s time to flower.
Infrared is important here because it’s the last light a plant will sense at dusk and the first at dawn. Having some infrared emitted by your grow light, therefore, helps cannabis set its internal clock and react promptly to day and night.
Without the infrared it will take the plant an extra hour or two to react to day and night, which on a daily basis all adds up to longer growing and flowering times and wasted electricity.
Blue
We mentioned that plants seeing a lot of infrared think they are overshadowed so grow taller. Plants seeing a lot of blue, on the other hand, think they’re getting plenty of daylight so grow short and sturdy, spreading out.
This is very helpful for the vegetative stage, especially when growing indoors where the height of your grow space might be limited. It also helps ensure the plants are getting plenty of light as more of each of them is exposed to that light when growing short and spread out, and the available light doesn’t have to penetrate so far.
Red
Yellows, oranges and especially plenty of red light are known to help cannabis plants transition to flowering and maximize the yield of bud. A lot of growers add extra red at the flowering stage. Some LED marijuana grow lights have a setting that allows you to do this very easily. Others have a full spectrum rich in red and blue that can be used for an entire grow cycle.
Green
While you might remember from high school science classes that plants are green because they reflect green light, they don’t actually reflect all of it. In fact, green light can penetrate further into cannabis leaves and further below the canopy than other wavelengths, making it important to photosynthesis and efficiently nourishing the entirety of your crop.
When picking marijuana grow lights, make sure your chosen light has at least a little green in the spectrum.
Marijuana Grow Lights: What is Quality?
Early LED marijuana grow lights focused heavily on red and blue light, to the exclusion of other wavelengths. However, modern LED lights usually provide the full spectrum. When you’re choosing one make sure to verify that this is the case
Watt?? Watt For??
Some other tips to ensure you’re getting a top quality marijuana grow light:
- Don’t be fooled by wattage. When it comes to LED grow light specifications this is one of the most confusing areas.
- Firstly, wattage is not a measure of brightness, only of how much electricity a light draws at the wall. This isn’t just true of LED lights. However, it is often quoted as if it’s a measure of brightness.
- Secondly, an LED grow light’s quoted wattage might refer to either one of two things (this has yet to be standardized across the industry). For instance, a 300W LED grow light could be either one that draws 300W at the wall or one that is equivalent in brightness to a 300W HID grow light. Because LEDs are more energy efficient than HIDs, the latter “300W” LED light will likely only draw around 185W to generate the same brightness as a 300W HID.
- So pay attention to exactly what is meant by an LED grow light’s stated wattage, and use it only to judge how much your electricity bills will be.
LED Chips (Bet You Can’t Use Just One)
- Pay attention to what LED chips are being used. You’ll see 10W chips and higher, and some of these are pretty good. However, 5W chips are currently the most mature technology and will provide as much brightness and intensity as you’ll need. With the right lenses and reflectors some of these are actually more intense than some 10W chips.
- LED chip brand is important too. CREE, Epistar, Bridgelux and Osram are reliable names for marijuana grow lights. CREE LEDs are especially sought after.
- The best LED marijuana grow lights will have reflectors and/or optical lenses to properly focus and intensify light from the diodes. Cheaper lights without these can still be pretty good, but the former should give your plants a brighter more even light coverage. Here is an example of a good light with special lensing to make an even light distribution:
Other Features & Specs to Check
- If the grow light has an internal fan, check how many hours it’s rated for. It should last at least as many hours as the LED chips (usually 50,000 to 100,000 hours).
- If the light is designed to dissipate heat without a fan, all the better. One less moving part to go wrong. Again, this tends to be a feature of more expensive lights.
- Another thing you’ll usually pay extra for is different grow settings. For instance, the ability to dim the light or change its color temperature for different grow stages. Which helps you to maximize yield and minimize energy used.
- Some top end lights are even programmable, often via WiFi and a smartphone app, to mimic the sun even more closely (for example, the LED light below). We’ve even seen some that go so far as to ensure that not only is infrared light in their spectrum but that it’s also the last light the plants see at night and the first when the lights come back on. Here is an example:
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- Always check PAR diagrams! If the diagram only shows PPFD for the center of the grow space, be on your guard. If they haven’t given the PAR values across the light’s whole footprint, it may be that the light coverage is not very even. Unscrupulous, fast buck manufacturers often quote brightness very selectively.
- In fact, the more specifications provided the better. Period. It’s usually a sign of a more trustworthy, better quality manufacturer with nothing to hide.
- Likewise, a long warranty is another good sign. A five year warranty is outstanding, three is great, two is fairly common.
- Some manufacturers will give you specs for ratio of light to energy, or in other words efficiency. A measure of 1.5μmol per joule of energy or higher is great. Some of the top marijuana grow lights are highly efficient at around 2.3μmol/j.
- Ideally, make sure you know what sorts of marijuana strains you want to grow before buying your light. Different strains have different optimal light requirements, so you’ll want to be sure that you’re getting a light that can give them what they need across your whole grow area.
- What driver does the light have? A constant-current driver (rather than constant-voltage) will extend the life of the diodes. Most marijuana grow lights should have a constant-current driver these days, but check and make sure.
That’s a lot of things to consider, we know. But we can simplify it for you.
The Simplest Way to Choose Marijuana Grow Lights
Don’t worry too much about the exact spectrum of your grow light. What matters most for cannabis plants is how much light they’re getting.
Ideally, you do want your marijuana grow lights to be full spectrum…
But in general a bright light with plenty of blue and red will perform better than a dimmer light with a fuller spectrum.
So, first and foremost, look for brightness (remember: PAR/PPFD, not lumens or wattage). The brighter the better.
Buyer Beware
However, a caveat: manufacturers almost always describe their light in terms of wattage, meaning the equivalent to HID light at X watts. For whatever reason, this has not changed much, even though it makes little sense. In general, you can assume that an LED sold as a “300 watt” light will actually draw around 60% of that amount of power at the wall. Whether it will give you the light you need is a question that is best answered by looking at the actual PAR value and coverage graphs. Here is an example of a light with the information you need to make a good decision.
- COB LEDS- COB is known for high power and stability. COB, higher brightness, smaller thermal resistance, less light attenuation and longer life.COB itself is a full spectrum design with high PPFD value which can promote faster and better plant growth
- EXTREMELY HIGH PPFD- PPFD, Photosynthetic Photon Flux Density，Hanging at 18", the PPFD is 941 umol/m²s. The bigger the density, the higher the value, the better the plant. COB LED has highest PPFD output. COB LED is much brighter and more efficient than traditional LEDs.
- FULL SPECTRUM- The COB LED itself is a full spectrum lamp integrated design bead. We have added additional light beads in various bands to ensure the scientific full spectrum. It contains 2pcs COB, 40pcs 630-660nm, 6pcs 470nm,5pcs 6500k, 3pcs 3000K, 2pcs UV, 2pcs IR
- MAXIMUM ENERGY SAVING- The actual power is 245watt.Best hang height at 24",Core Coverage area at 40"*40"(3.3*3.3ft). Maximum coverage area at 42"*42"(3.5*3.5ft). It is more scientifically and energy-efficient than HPS HID and MH. It serves both herb/veg/bloom and is convinient for you.
- BEST SERVICE- We are a professional LED light manufacturer with strong R&D team and many light tester. 2 years warranty plus 30 days money back guarantee. If you have any problems, please feel free to contact us. We will provide you with completely satisfing reply.
You can look at the PAR value chart on this light to make sure it gives good even coverage. Then, look at the spectrum. There is a chart for that too. Finally, these are CREE LED’s which are among the best available.
And if you’re still faced with a choice between similar marijuana grow lights, or money is tight, check what wattage the light will draw and go with the one that will keep your utility bills down. That’s why manufacturers still put wattage in their light descriptions.
That’s as simple as we can make it.
However, if you can afford it, spending a little extra is usually worth it with LED marijuana grow lights. While there are some bargains around, mostly you tend to get what you pay for.
Best Marijuana Grow Lights For a Beginner
Best is very subjective, of course… but also very simple. The best LED marijuana grow light is the one that’s best for you. The one that best meets your growing needs and growing style.
If you’re someone who likes to experiment and optimize, you’ll want a light with plenty of features and programmability. If you want to keep things simple, a good, no-frills, full spectrum light that you can use for the whole grow cycle will be best. Or if you’re on a budget, you’ll likely want one that gives you plenty of brightness for the power it uses.
A Final Word from MaryJane Farmer
Hopefully now you’re a bit less confused about marijuana grow lights. And perhaps you’ve even settled on the one you’re going to start growing with or upgrade to. You can find reviews of more LED marijuana grow lights on our home page. Our reviews cover all manner of lights and prices. And we have another review for Budget Lights.
If you’d like to know more about growing, we have a Free downloadable beginner’s guide. And we also take you through setting up a grow area.
MaryJane Farmer sez “Send me an electric mail with photos of your grow and I will post them on our site. Good karma to you.”
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Last update on 2023-02-20 / Affiliate links / Images from Amazon Product Advertising API
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