Grow Light Guide

What type of light do plants require?

This is an in-depth grow light guide explaining what the different spectrum’s of light can do for your plant. Learn what to look for while buying a grow light with some tips and tricks along the way.

With all the brands out there claiming to have the number 1 product, how do we know who’s telling the truth? Well maybe the truth is, there is no number one light for every situation. Some may be better for smaller closet grows while others for larger to commercial growing, some may sprout killer tomatoes while others may be more suitable for your medicinal plants.

Everybody first starts growing with the basic knowledge of blue for seedling/vegging and red for flowering in terms of light. This is fine and will get the job done but this is just the basic necessities when it comes to giving your plant the light it wants. Growing with hydroponics is an art, it requires planning, extreme attention to detail and most of all, passion.

How do plants use light?

Plants use light a couple of ways. They can sense light intensity, color and duration and use the information to determine where in the year it is. Plants do this with their Phytocrome system. As you know plants sprout in Spring and die in Fall. So in-between these seasons, is the plants time frame to grow and flower. This makes a plants ability to determine the time of year important for determining what stage of its life it should be in. Plants can use their Phytocrome system to remain in a life stage longer if need be. For example, a plant will remain in vegging stage until it knows it can receive enough sleep and red spectrum to flower properly.  Plants can also go the opposite way and speed up into flowering stage if the time frame for flowering is getting smaller due to season change.

Plants also use light for photosynthesis.  This is the term used for plants using light energy to create food. This is done by trapping light energy in it’s chloroplast’s (cell structure designed for making food) and using that energy it makes a chemical reaction, producing glucose. Glucose can then be stored or used as building material. Plants absorbs the energy it requires through it’s pigments. In a plants chloroplast there are different types of pigment, each pigment absorbs different wavelengths. The main pigment of any plant is called chlorophyll a.

What color spectrum should i grow with?

Most growers use Kelvin to measure the color of light. Kelvin is a measurement that gives you the perceived color of light. Plants however, do not absorb light based on the colors we humans perceive light as. For example, you can buy a light that is rated 2700K which is warm red but it can actually be made up from a variety of wavelengths. This makes kelvin not useless, but inefficient.

Different plants and their various growth stages require different colors of light to grow efficiently. Why is that? Well when we take a plant away from its natural habitat, we want to create a synthetic habitat as similar as possible to what that plant is used to. I cant say iv’e ever grown my own tomatoes or even a flower, (although they’re not completely different) i’m going to stick to what i know.


Seedling stage – what color is your little one stretching for? well, growing season starts in February, and in February plants can get up to 18 hours of light, but many growers prefer a 24 hour light cycle during the seedling stage. If you’ve noticed, the light we get from the sun in February is very intense and bright yellow in color, making 5600K – 6700k the optimal temperature when choosing the bulb’s for your grow lamp.

Vegetation stage – In the great outdoors, plants will be in vegetation stage from late march, possibly all the way up to early august. During this time there is a mixed spectrum of light, This is where full spectrum grow lights come in very handy. So if you’re not lucky enough to have a full spectrum grow light, then a mix of 6700K and 2700K is what you want to beaming on your plant.

Flowering stage – The stage every grower waits for, the stage where your plant starts producing flowers/buds. Plants in their natural habitat will start this phase late July/early August. During this time days get shorter, winter depression starts sinking in, and you start seeing red skies at night which translates to “a growers delight.” This is when you would switch to the 12/12 hour stage to compare with Fall’s shorter days. The sun isn’t so bright anymore either, almost appearing as a reddish orange. So why would your plants what any different. during this time 2700K is the optimal light temperature, although some growers still like to throw in some higher temperature light as well to maintain some help to the roots and branches.


Nanometers or (nm) are measurements for specific wavelengths (bands of light). In the picture you see beside this, is the scale of nanometers that make up the visible spectrum of light waves. Each wavelength of light is also called a “band”. This is the preferred way of determining the light your plant is receiving.

What are bands in a grow light?

Every wavelength of light triggers photosynthesis slightly different. Some wavelengths are absorbed much easier while some bounce most of the light energy off. So should you just stick with the wavelengths that absorb the best? No. Different bands of light are absorbed through different pigments, those pigments then send different responses to the plant on how it should be behaving and using that energy.

Blue wavelengths – Blue light is absorbed by the pigment chlorophyll a.  Blue light triggers the plants to focus it’s energy on it’s roots and stem growth. When your plant seems to be stretching toward the light source, it is because it is trying to get its fill of blue light. Having a high amount of blue light will ensure it grow thick bushy and short (depending on the strain.) Keeping a higher then usual amount of blue through the flowering stage will also help control it’s height. Beware though, as complete blue or too high of a percentage of blue will result in a reduction of leaf area.

Red wavelengths – Red light is also absorbed by the pigment chlorophyll a. Red light triggers a plant to focus energy on leaves, flowers/buds. If you have too choose on one light throughout the plants life, red can be used. Only giving your plant red light may make the plant stretch for more blue light. Without other wavelengths that plant will not grow to it’s potential.

goblin hydro nanometer scale for indoor gardening

How many bands of light should a grow light have?

6-8 bands of light in an Led grow light is the most efficient amount for regular grow operations. Within those 6-8 different light bands should be mainly red and blue for the main growth development. An assortment of other wavelengths should be added as supplemental growth boosters. Using less then 6 wavelengths will result in your plant receiving less energy then it is built to . Using more then 8 wavelength’s will usually result in insufficient energy coming from the required wavelengths.

Lets compare plants to humans. Think of blue and red light wavelength’s as a plants main food source essential for growing and developing. The other wavelength’s are like vitamins, your body uses different vitamins for a variety of aspects of your overall health.

Do the amount of watts per led chip matter?

No, doesn’t matter if you have 300, 1 watt chips or 100, 3 watt chips, they end up using the same amount of watts, giving the same amount of light. Although the brand of the chip is a big factor when it comes to lumens per watt.

What type of grow light should i buy?

One of your first decisions when deciding on a grow light should consider the space your plant will be in. This will probably be the main factor in which you choose the way your light is produced. For example, a high powered, high temperature HPS would not be the best choice for you little cannabis seedling sprouting in your closet, and LED would not be so efficient in 1000 sq warehouse that looks like a jungle. So lets look at the different ways light is produced and what their suitable for.

The main source of light cultivators have used for medium to larger scale grows have been HID, due to the their coverage area per lamp. Fluorescent has been the choice for many small time/ closet growers, due to it’s low price per watt, and low heat output. That being said, times are changing and i believe LED grow lights will be the main source of light for cultivation’s of all sizes. If you look at the table above you can see the four sources of light, grow lights are created from. Each source of light has different behaviors, advantages and disadvantages. These are rough equivalences based off the average bulbs. some grow light companies have built them more powerful or to last longer. Another consideration when buying a grow lamp based on wattage, is that lumens are the true measure of light. Some lights that use the same amount of wattage may put out a different amount of lumens.


The number 1 reason LED is growing in popularity is efficiency. Although their shelf price might seem a little steep, on average an LED uses half the energy to create the same amount of light as it’s competitors. For example, an Apollo’s full spectrum 600W grow light compares to a traditional 600W HID, while only consuming 285W.

Heat management is also another selling point on these puppies. With traditional lamps, 95% of the energy is transferred into heat. LED’s also create no IR radiation. While most of these lamps can be cooled using a small built in fan, some companies are creating a vibration system to dissipate the heat, (you can learn more about this on the LED page.)
Lifespan of LED also greatly outlast any traditional lamp on the market with the average lifespan being 50,000 hours. Yeah, not to much to say about and/or against that.

As i said before, these guys can cost a pretty penny. Now is that penny worth it? YES, yes it is. With all the reasons mentioned above, which is just dipping into the facts, you’ll end up saving your money in the long run

no name light with full spectrum


Fluorescent lights might not be the bell of the ball, but they do have they’re

uses. Their cheap, probably the cheapest alternative you can use. You can buy them anywhere, from Walmart to actual horticulture shops. They come in either bulb form or tubes. Both forms do require the use of ballasts. Fluorescent tubes are held in place by a fixture which usually has it’s ballasts inside. Bulbs have the ballasts built in above the socket.

Main purpose for most growers would be for seedlings and clones. Like LED’s, there is not much heat that radiates off them within a couple inches from the plant. Some closet growers can and do, use these as the main light source all the way through. I and most others however, prefer to use them for seedlings and getting at those hard to reach areas your main light just wont reach.


Here’s contender that is giving LED a run for its money.  Why? in short, light spectrum. these lamps give off a pretty complete spectrum, great for vegging, and decent for flowering. You’ll learn more about light spectrum below. Another reason there blowing up the market is the deep penetrating light they produce. This means you can place them higher off the plant. More then CFL’s and most LED’s, just not HID’s. Energy-wise, they are coming pretty close to LED’s at 30 – 40 thousand hours while still trumping HIDs and CFL’s. Whats the downside? price, the price of these can bleed your pockets dry, especially if your graduating from you closet.


Easily the most used grow light throughout time. Their cheap, powerful and… well they’ve been around forever. Most common HID would probably be metal halides, i’m sure you’ve heard of them. These would not be so suitable for your closet as they give off massive amounts of heat. You can buy them in packages with a reflector and a fan, but you’ll probably need an entire ventilation system added on to control the temperature. Their most popular with medium to large size grows because of the extremely deep, penetrating light they give off. you can place them higher above your plant then any other light and you can bet your life that it will reach every leaf of that plant.

custom grow room with hid lights

What are the best grow light brand names?

Do brand names matter? of course. Like any other product, in the land of horticulture you get what you pay for. You wouldn’t go out and buy a Hyundai and expect Mercedes quality would you? Some people say “your just paying for the brand name,” but have no idea what that brand name really inquires. When a company puts money into their brand, they don’t want some cheap knock-off people buy once to then move on to some other brand.

The top grow light brand names have spent thousands of dollars investing into the latest technology and researching new technology that makes them stand out. Every month some horticulture brand comes out with a lamp that has a new feature. Most of the time it’s a small trinket added. Some of the time it’s a real breakthrough. Heat sinks for example, conduct the heat away from the light, to the heat sinking material. You can check out our blog to see the latest and upcoming horticulture technology.

So whats the best grow light brand out there? hard to say. Each brand has it’s own strengths and weaknesses so it really depends on what your looking for. One thing that’s important to state – more expensive doesn’t always mean better. However this IS a review site, so if you have a brand your leaning towards check out it’s review page and see what we, and other people had to say about them.

What kind of warranty should a grow light come with?

This is always important to take into consideration when buying anything. Grow light companies usually offer a standard 2 year warranty and if they don’t, then move on to another. Always read the warranty specifications, does it cover a single led element burning out? How about the heat sink loosing conductivity? what if one of the fan bearings wear out? It should cover every single component no matter how small or cheap.

Warranty is important but you shouldn’t be expecting to use it. Reviews on other peoples experience’s is the best way to get an idea of durability. Even if they haven’t had to use their warranty yet, anyone can tell when cheap materiel was used.

Are grow lights upgrade-able?

Upgrade-able parts are nothing to overlook today. Technology is gaining traction, you can end up spending a bundle on the best product on the market just to have new technology come out days later. Not every brand is designing with room or ability for improvement, so the ones that are you should take a heavier consideration on. The ones that are have a modular build, meaning it is made up of sections instead of one solid piece. Getting more advanced and we can start looking at independent circuitry. Independent circuitry maintains the voltage or current regardless if one components die. Led’s do die, that will never change, but now you can replace them individually when they do.


When you buy a new grow light, their are usually accessories it comes with, or you can buy for it separately. The question you should be asking is dependent on the set up your creating or adding to. Well if your creating your setup, your definitely going to need some of those accessories. We should probably talk about some of them. This site is about lighting setups though, so i will be skipping most that is not directly correlated to light fixtures.


grow light bestva modular fanAs we know all lights create heat and heat kills plants. So obviously we need a way to dispose of this heat. Fans are the most common way of doing this, or at least transferring the extra heat elsewhere. Each fixture, whatever the kind, has it’s own severity of temperature you’ll need to dispose of. Again, your setup will also affect this equation.

A lot of them, mostly LED, now come with their own built in fan. LED as we know don’t generate much heat, so we don’t require a whole ventilation system solely based on temperature. So this is an important feature to look at when making a purchase. Built in fans add great support, but unless your cooking up a couple seedlings or clones, they should not be your primary solution. For HID, we do require quite the ventilation contraption as they heat up a considerable amount.


Reflectors are basically backboards that reflect the light into the direction of the plant so your not wasting those precious rays. Most HID kits come with their own reflectors or they give you the option of purchasing one designed for that specific light. As simple as they sound, there are all different types, shapes and sizes made from different reflective materials.


Not to much detail we can get into about these. Timers are plugged into your light and used to set the hours you want your light on and off…Bet you didnt see that coming. Timers are very handy for you light schedule if your not sitting at home all day, every day. Not much to get into on what brands to go for but the one thing you have to look for is how much power it can handle.

Nutrient Analyzers

Nutrient analyzers are sensors you can put into your soil or water mix to detect the levels of nutrients. Common nutrient levels they come equipped to detect are ammonium, calcium, sodium, nitrate, potassium and chloride. This works hand in hand when you combine it in your grow room management software.

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