Bulbs with a more yellow/red tint are listed as “Soft white” colored with a Kelvin of 2700K. These “low kelvin” bulbs are optimal for the flowering stage.
Each plant should be covered by around 10,000 lumens per plant or even more. So if a bulb gives off 2,500 lumens, you’d need 4 or more of those bulbs per plant for optimal light coverage.
Kelvin is a scale which is used to reflect “color temperature” which is a fancy way of expressing the frequency (color) spectrum given off by a particular bulbs.
These CFL bulbs mimic the color temperature of the sun during Fall/Winter.
Generally… more wattage = more light = faster growth = bigger yields.
You may also want to look at “lumens” to understand light output. This is another way to measure light output and is often listed on the package of your CFLs.
Vegetative Stage – 5000K / 6500K
They’re completely separate measurements, as I will explain below.
Remember, more light = plant makes more energy = more yields.
A good example of this is the fact that many bulbs are still marketed using “lumens” as a selling point. While lumens are a measurement of light quantity, it is not an appropriate term for horticultural purposes.
Greetings to you, Nico!
I have searched the web and noticed that you are the guy to ask about indoor lighting for cannabis horticulture. My question is rather simple, I think: In terms of lumens, what light output do I need to grow a plant or two successfully in my home? I have a small bedroom and am thinking of using a ’ x 4’ or 4’ x 8’ grow tent? Any suggestions on bulb types and strength would be helpful! Many thanks & good luck to you! — Jonathan V. via the mailbag at [email protected]
Lumens would be used to describe the strength of light if you were trying to light a stage or illuminate an object for viewing purposes. However, for photosynthetic purposes, the proper quantification of light uses PAR values, which stands for “photosynthetically active radiation.” This measurement of light provides information on both the quantity and quality of light being emitted by a source in relation to its effectiveness and efficiency for the plant’s photosynthetic processes. It takes into account not only strength, measured by photon count, but also spectrum, measured by color or wavelengths.
The solution is simple: a 400-watt or 600-watt will serve you and your plants much better. A 400-watt HPS puts out approximately 50,000 lumens. With a 16-square foot footprint in a 4’ x 4’, that’s 3,125 lumens per sq. foot. A 600-watter is roughly 80,000 lumens, giving 5,000 lumens per sq. foot in the same tent.
Ideally, a marijuana plant should have 4,500 lumens to ensure maximum growth. A 4,500-lumen bulb will cover a 3×3-foot space with adequate lighting.
Maximum Yield Explains Lumens (lm)
Lumens are the amount of light a bulb provides. Essentially, lumens mean brightness. The higher the amount of lumens, the brighter the light that will be achieved. Plants, especially cannabis plants, require adequate light to grow. Typically, one cannabis plant needs at least 2,500 to 3,000 lumens.
Many growers first starting out tend to get confused between watts and lumens. Watts are the amount of energy a bulb consumes. Even if a bulb has a high wattage, it does not necessarily mean that it will produce high lumens. This is especially true with new high-energy LED lights because the amount of wattage does not guarantee a brighter light.