Plant Grow Lights – Which are Best?

Lighting Basics

I’m going to teach you some basics so pay attention, there will be a test on this later on. Plants absorb light along with carbon dioxide, converting the light energy to chemical energy through a process called photosynthesis. The plant grow lights Photosynthesis Diagramspectrum type, duration, and intensity all play key roles in vegetative, flowering and overall plant health.

The Perfect Intensity

When you are doing it right, plant grow lights provide adequate light, so plants continue along their life cycle as nature (the grower) intended. When too little light is available, plants will grow tall, elongated stems because the plant is stretching to find additional energy rather than producing leaves to harness the available light.

The problems with stretching is two fold. First it makes your plant tall and thin which can be a problem if the you are growing in doesn’t have enough height to accommodate your plant. Second is it will significantly lower your plants yield because the plants energy was wasted on growing tall instead of producing more buds.

A lot of stretching isn’t gonna work for your indoor plants. You can’t just put any old 1000 watt plant grow light over your plants and call it good, a careful balance must be made between the amount, type, and duration of light produced.

Duration is the Key

What a lot of people don’t know is cannabis plants perform a portion of their growth during the dark hours so it’s best not to have light all 24 hours. 18-20 hours of light is recommended. As you probably already know, shortening the duration of a light will trigger flowering. It’s recommended that an equal balance between light and dark (12 hours of light, 12 hours of complete darkness), be maintained during the flowering phase for best results.

When it comes to indoor plants, even just a few hours under a LED light will produce the best houseplants. By providing additional red and blue spectrum light produced by plant grow lights, you are giving your plant what it needs to thrive.

If you want your house plants (not marijuana) to grow to their full potential its best if you provide a full day of light from your chosen source. This can be achieved best with LED, followed by MH/HPS, then Fluorescent as far as performance goes.

Be sure to research your plant’s requirements when setting the height of your LED light(s). Too close (within inches) will cause your leaves to burn. It’s best to maintain 18 inches of distance or more depending on the power of your light or whether it has secondary optics which focus the light directly vertical of the light.

I prefer to keep my lights a couple feet or more over my younger plants because it encourages the plants to grow in height and when they reach the desired height, that’s where the light will remain. In fact, the healthiest houseplants I have are LED grown.


Lighting Types

FluorescentsFluorescent Grow Light

Fluorescent plant grow lights produce a cool blue light and are low heat and can be set very close to the tops or canopy of plants which make them a good choice for seedlings. Fluorescents are fairly cheap and come in a variety of styles and sizes though most commonly sizes used are T5, T8, and T12.

Pros: Inexpensive, cost-efficient, long service life, low heat production, and ideal for the seedling stage of growth.

Cons: Produces a narrow spectrum of cool light that poorly promotes a flowering response in plants, contains hazardous materials.

Metal Halide (MH)Metal Halide Grow Light

MH plant grow lights produce cool light in the range of 2700 to 5500 Kelvin and very closely mimics natural light. This makes it an obvious choice for promoting vegetative growth. Excessive heat produced requiring fans for cooling the surrounding atmosphere.

Pros: Very close to natural sunlight spectrum & effective during the vegetative growth stage.

Cons: Uses a lot of power, require high frequency ballasts, can be expensive, excessive heat, and a short lifespan.

High-Pressure Sodium (HPS)High Pressure Sodium Grow Light

HPS plant Grow lights produce light in the red end of the spectrum which is a reproductive trigger in plants. These lights are often used during the flowering cycle and work considerably well but they produce excessive heat which generally requires fans for cooling the surrounding atmosphere.

Pros: Great flower production during bloom phase.

Cons: Grows taller, thin plants, causes discoloration in leaves, produces a lot of heat, somewhat expensive, requires high frequency ballasts, short lifespan.

Light Emitting Diodes (LED)LED Grow Light

LED plant grow lights are the present and future of indoor home and industrial growing operations. They consist of low-wattage LEDs that are arrayed on a circuit board in many different formations to effectively produce light. LEDs are exceedingly energy efficient and have a very long lifespan (up to 50,000 hours or more).

LED plant grow lights are able to produce Blue (430nm-450nm) and Red (640nm-680nm) spectrum points simultaneously without any other inefficient wavelengths. LED’s do not produce excessive heat like other lights, so you don’t have to use such a big cooling fan for ventilation. Hands down, the best for indoor plants during all phases of development.

Pros: Can produce dual-band color spectrum (red and blue) at the same time as well as full spectrum light, most energy-efficient of all grow lights, generates minimal heat and promotes an overall sense of awesomeness.

Cons: Used to be expensive but recent changes in their manufacturing process has lowered prices tremendously.



Okay, time for the test. Just kidding, there is no test, you made it this far so give yourself credit. But can you see why LED’s are the best plant grow lights? Heat, poor efficiency, sub-standard color spectrum, even more heat (Because MH & HPS get HOT!), short lifespan, etc., those are things you don’t need to worry about with LED’s.

As you can probably tell, I am a big fan of LED grow lights, and my experience says they are the best. But what do you think? I’d love to hear your thoughts or if you have any questions please let me know in the comment section below.





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  1. Ciara

    Thank you for your highly informational post about lighting for these cannabis plants. I’d like to start growing this winter, and I’ll definitely be looking into LED lights (they look like the way to go!): easy on energy use/cost, efficient, and they also put out the right wavelengths for photosynthesis! Amazing! Do you know if heat is a requirement for optimal growth of marijuana plants? Thanks!

    • Karl Hosch

      Optimal growth occurs between 68-77° Fahrenheit with humidity between 40-70%. If you are below that amount, the plants grow slower and if you are above, you will need to add more fertilizer, water, etc. Because the metabolism is higher. 

      Since you are indoors, the little heat generated by the lights will keep your plants within that temperature range.

      Yes,LED’s are the way to go because they are best in every way. The main complaint when they first came out was that they were but if you check my lists, they are cheaper than the HPS and MH systems. Thank you for visiting my site, if you have any questions or need help this winter, feel free to come back and see me. Best of luck! 

  2. Awesome information. May come in super handy soon. I grew years ago. Keep up the great work.
    I have fabric from Colorado with some nice leafage on it. Lol

    • Thank you. It’s a good time to start growing again, there are a lot of new advancements in the industry, lighting only being one of them. Feel free to come back and visit or contact me if you have any questions on your future grow! Thanks again!

  3. Jacqueline

    This is a very interesting post!!
    I have heard about plants liking natural light or more so, the instructions on some of the indoor plants I’ve purchased suggest placing the plant near to a light source – such as a window where natural light flows. However, I wasn’t aware of the different types of lights and the effects they can have on how a plant grows.
    I have learnt something new today!!!
    I have a Kentia plant which is from the palm tree family. With palm trees being synonymous to the Caribbean, do you think I’ll have a hard task in keeping this alive for years to come or will I need to invest in one of these lighting systems?


    • Karl Hosch

      The Kentia is native to Australia and generally tolerates low light levels. You should not need any additional light for this plant. Indirect sunlight will be fine. They are very hardy and forgiving. Just make sure not to over water it. With just a little maintenance, you should have a healthy thriving Kentia plant for many years to come. Thank you for your comment, let me know if you have any other questions, I am here to help.  

  4. Norman

    It is interesting to see how the world looks at this plant, I once looked at it in the seem light but what is so amazing is that this plant can and has been used for medical reason helping persons. Your readers will learn a lot from what you are sharing with your post and I am sure they will like what you are sharing.

    • Karl H

      Yes, I thought the same way until I found out that an uncle of mine was diagnosed with terminal cancer. The doctors had given up but his son did not. He searched for a cure and found marijuana in liquid form and my uncles cancer has been in remission ever since. It was a real eye opener for me. Just one instance of proof that the power of a positive mind can make miracles happen. Thank you for your supoort and sharing your insight!  

  5. cbuffone

    Hi Karlito,

    I just read your grow-light-basics.

    A very informative article.

    I am looking at adding a greenhouse and your insight provides me with some alternate options on lighting – Your points on high quality yields identifying the various growing stages is very helpful.

    I conclude that to optimize growing in my greenhouse in our location and climate (I am in the Great White North, of Canada) I will need to utilize two types of lighting for the various growing stages to optimize plant growth.

    My son did some research on light capture systems but unfortunately they do not appear to be a viable option at this time.

    • Karl H

      If you are referring to an outdoor greenhouse as opposed to an indoor grow tent, your growth stages will be determined by the sun and the amount/duration of available light. It depends on how far north you are as to the duration of each cycle. Your main concern if you are using an outdoor greenhouse will be maintaining the appropriate temperature and humidity. You can use HPS or MH to raise temps but the evolution tells us the sun is the best light source overall. If you plan on an indoor grow, where you control the light, then LED’s will work fine alone but if you needed heating, yes, in addition to LED’s, I would include MH during vegetative then HPS during flowering. Keep me posted once you get going, I’m here to help. Thank you for visiting! 



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