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can you grow weed with a light bulb

Can you grow weed with a light bulb

Do this math with your LEDs as well. The PL Light TopLED is 320 watts so the BTUs will be 1092 BTUs. While that looks like a big savings it will take at least two times the amount of our LEDs to get to the same light level as a 1000w HPS. On the other side of this argument is that the LED fixtures do not provide the radiant heat as HPS and your crop roots will perform better with warmth. It is proven that there is a direct correlation between heat and crop production. Plants grow slower, producing less fruit the colder they are. In northern climates many growers rely on the heat from HPS to warm their crops.

When comparing both technologies, always compare light levels of the entire grow and not just fixture to fixture. I cannot stress enough that there is no such thing as a 1-for-1 replacement of HPS by LED! That simply does not exist in the marketplace. Yes, there are LED fixtures that exist when measured directly beneath the fixture. The output looks equal to or even greater than an HPS. But, when you move the PAR sensor any direction from centered beneath the LED the light level decreases much more under the LED than any HPS fixture!

The best advice I have is to get a comparison of your ROI done by a versatile company. One that can offer both technologies where you can have light plans designed to the same levels with both technologies. Don’t trust just what the LED guy says or the only HPS guy says. Look at both, do your own math. Know what works for the strains you are growing and measure your own ROI. The easiest way to do this is going to this link and ask your local PL Light Territory Manager for advice as we are the “Lighting Knowledge Company” and whether you decide to use LED or HPS, you will get a true and honest comparison of both technologies.

Light Planning

In countries like Canada, where the federal government has legalized recreational cannabis, there is the ability to do more research. The University of Guelph is one organization that is leading the way in this research. As he states in this article from HortiDaily — Michael Dixon, Director of Environmental Control Research at Guelph says: “We have found that the optimal LED spectral recipe changes with every strain of cannabis.” This is a very important statement for growers to consider! Will you be growing just one strain in your grow the entire time? If not, what spectrum do you choose? Yet if the added blue light in flower only increases your THC levels by 4% is there a justifiable ROI in the cost of the added light spectrum?? If so, can you do that by just adding a few MH lamps? Or does the ROI make sense to go all LED? (1000w DE MH lamps are now available with the PL Light NXT 1000w DE fixtures).

The bottom line that I can share with you, from my perspective where I get visibility to lots of opinions on the topic, see lots of sales and growth cycles, talk to lots of growers, is this: We are still in the investigative and development stage with LED technology in this sector.

To use the PL Light TopLED R/MB as an example: 320W fixture with PPF of 860 μmol is 2.7 μmol/J (860 / 320 = 2.6875) where the 1000W DE HPS has an output of 2100 μmol is 2.1 μmol/J (2100 / 1000 = 2.1). This is important because I have sat in many presentations, by LED manufacturers, who show how quickly they can hit a good ROI with their LED and use 1.85 μmol/j as their HPS comparison. They’re not lying about this but they are using the old single-ended screw in 1000w HPS lamp in the comparison. These lamps have an output of 1850 μmols at 1000w. But, it is an old technology only in use by small hobby grows these days. I have seen manufacturers use as low as 1.7 μmol/J for HPS which would be the equivalent to the end of life of the old HPS technology.


What about growing in a greenhouse? From our graph above showing the spectrum of sunlight compared to that used for photosynthesis is there any benefit for using a light source where you can dial in the spectrum to add more blue? The natural light received by your crop in a greenhouse will cover all of your light spectrum needs. So the big question for greenhouse grows should center more around the ROI comparisons between LED and HPS — not about light spectrum needs. This is not something you will hear from light manufacturers of LED lighting. Your LED-only supplier will have you believe you NEED their spectrum specifically!

With LEDs most will use μmol/J (“Micromoles per joule” with joule being a measurement of watts). This is easy math you can do yourself.

Can you grow weed with a light bulb

For growers who are looking to harvest 1/2 to 1 ounce of cannabis a month, LEDs may be your best choice. At this size, they are super low on electricity, run cool and need almost no setup! They get better yields than fluorescents but don’t run as hot as an HPS of similar wattage.

“LEC” and “CMH” both refer to Ceramic Metal Halide grow lights, which is a type of HID light that is a bit more efficient than a regular Metal Halide light

The light from a Metal Halide appears a little bluish, and is well suited to growing cannabis plants in the vegetative stage

More Light = Bigger Yields!
(up to a point, it is possible to give your plant too much light!)

Cannabis plants under a T5 grow light – when plants are trained (like these ones in a Scrog setup) you can get pretty decent yields from fluorescents.

Ceramic Metal Halide (CMH) & Light Emitting Ceramic (LEC) Grow Lights

Cons of Fluorescents

Note 2: Incandescent light bulbs (old fashioned light bulbs) are NOT suitable for growing marijuana!

CFL Grow Lights