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. Karl, I’ve had the opportunity to work on some of the big marijuana grow operations here in Denver, CO. Acres of plants in warehouse buildings, truly amazing operations. I did notice that some of the rooms have a little different lighting colors. Are there better colors for different strains? I.E. warm lighting as opposed to the cool lighting. Thanks for the info, you certainly know the ins and outs of LED lighting!


  2. Azzee

    I have multiple indoors plants which are not vegetable, all are house plants. I have bought one LED 50 Watt which has lots of LEDs but it is warm light but I have seen grow light look like red and blue output color, so can I use this light for indoor plants.

    • First I would look into the light requirements for each individual plant because too much light can destroy the plant. 50 watts is okay for most house plants except perhaps plants like ferns which require less light.

      If the light is putting out red and blue light it is likely a grow light. But not all grow lights are the same because some put out different light spectrums based on the particular light requirements of the plant.

      For example, plants that are in the vegetative stage require more blue light and plants in the flowering or fruiting stage require more red light so without knowing all the facts about the light like what type LED’s, how many blue and red LED’s you have, it’s hard to give a recommendation whether it’s good or not.

      If you give me the manufacturer name and model of the light and the plant you are trying to grow, I would be able to be of more help. I look forward to hearing from you soon!

  3. You have certainly convinced me that I want to use LED’s, but I am unsure of what intensity to use. Are all of the LED Grow Lights the same?

    • The answer to your question is no, not all lights are the same. What distinguishes one from the other is power, secondary optics, and the quality of the chips. Experts suggest you use 45-65 watts per plant or per 2.5 square feet.

      You can take it a step further and find out the lights suitability for growing cannabis by its Daily Light Integral or DLI (mol m-2 d-1). To determine a lights DLI you need to know it’s PAR value (µmol m-2 s-1) which is the amount of light put out per meter per second. You take the PAR value and multiply it by 0.0864 which is the amount of seconds in a day divided by 1,000,000. This will give you the DLI value.

      For example the Advanced Platinum P300 puts out 683 PAR so 683 µmol m-2 s-1 x 0.0864= 59.0112 mol m-2 d-1. Cannabis grows best with a DLI value of 40-70 mol m-2 d-1 so you can see that the Advanced Platinum P300 is quite worthy of growing some good herb. I hope that answers your question, let me know if there is anything else I can do for you, I’m here to help!

  4. Remy

    growing marijuana has come a long way since I was last involved.
    I remember the days when we would just throw hundreds of seeds into the ground, scattered around the farm and which ever ones were strong enough grow we were grateful for.

    The attitude back in those days was to let nature takes its course. We didn’t understand much about what the plant needed or wanted. We just went with the scattergun, trial and error approach.
    I can only imagine what kind of difference all this technology would make to the final product.

    • Karl Hosch

      Yes, things have come a long way from those days. Every single little seed is counted on to grow and now they have them feminized so you don’t have to fool with the male plants. I think the advances in growing operations are mostly due to the fact that the plant is ultimately consumed and is now a viable medical product instead of a street drug. Thank you for stopping by, if you ever decide to start growing again, I got your seeds, soil, nutrients, and lights. All you need to provide is the water and the work. Take care! 

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