What light for pre growing outdoor marijuana

A question from a fellow grower:

I need to know what kind of light I need to use to grow in side until I ca get my plants moved out side .I would sure thank you for any kind of in sight you could give me .I just got a 4 foot by 2 light Luminaire articule de 1,22 m a 2 lumieres /Luz industrial de 2 luces de 1,22 m.What kind of buld should I use White finish cold weather start (o oF) Fiini blanc Fible (2) 32w .What kind of bulb do you recame mend me to use to start off with .I plan on puting it about 2 inches from my plants .I would like to konw what kind of bulb to use .I plan on starting all my plants this way so I can get a head start .Please tell me what kind of bulb is best to use .

I’m guessing this is a fluorescent light fixture. With almost any light for household lighting, the closer the type or color rating or color hue for the light, the closer it is to “pure white” or “true white” or “daylight”(these are some of the descriptions given) and it looks like pure white light to our eyes, then the light will have a pretty complete distribution of the wavelengths or spectra you need to grow a healthy plant.

A better or more accurate way of labeling these color hues is using the Kelvin rating and in this case a light fitting the above description will likely include a ‘K’ rating of approximately 5000K - 6500K, lower and the light looks too yellow/orange or reddish, and above these numbers the light looks too blue and/or green. Those are the things to keep an eye out for when looking for a bulb.

You’ll hear things like more red for flower and more blue for veg and so you’ll have people use the higher numbers around 6500 for veg, and some use a much lower number around 2500K for flower, this type of light is often called “warm white” light. Doing this with your average household lights is probably not very beneficial. The most important thing is overall lumens and enough of both red and blue to keep the plant healthy. Unfortunately blue and red do not look bright to our eyes, and so lumens is not the best way to measure how much red or blue light is getting to the plant’s leaves. But all things being equal, the brighter the light looks without looking too green, then you know you are also getting more blue and red light as well. Lights designed specifically for growing may have specifics of exactly how much of which wavelengths are present in the light, and then using their recommendation for veg vs, flower are warranted. But in general a light around the 6000k rating will be very good for both veg and flowering and would suit your purpose very well, especially since you’ll be flowering outdoors.

Here is some additional information that will help you know if you have enough light for various stages of development:

Seedlings and clones require about 400-1000 lumens per square foot.

Vegetative growth requires about a minimum of 2,000 to 3,000 lumens per square foot.

Flowering requires about 5,000 to 10,000 lumens per square foot, ideally, and can take possibly much more.

10,000 lumens is supposed to be about the average power of the sun at sea level on a clear day at high noon.

With fluorescent lights indoors, for vigorous fast growth and minimal stretching you probably want to maintain something near the horticultural standard of around 50 watts per square foot. Many people build their own CFL light systems using one 40 - 50 watt CFL bulb per square foot and this would fit into that industry standard.

1 Like