Fluorescent light is normally used during veg because veg doesn’t need as much intensity as flowering does, and it could depend on numerous factors as to why you might choose a fluorescent light over a HID light, but none of them are specifically because the vegetative cycle requires this light over the other. In general you need light with more blue in it for veg and more red in it for flower.
6500k is slightly blue shifted, 5000K to 5800k is considered kinda right in the middle, very balanced, and 2700k is red shifted. Those are some of the most common numbers, I’ve seen 3000 and 3500k as well. Pretty much anything above 5000k to 5800k is blue shifted spectrum light and below is red shifted. Yes, in flower, using fluorescents, in general more 6500Ks are used in veg and more 2700Ks are used during bloom/flower.
Chlorophyll absorption peaks are 430 nm and 662 nm for chlorophyll a, and 453 nm and 642 nm for chlorophyll b. Chlorophyll b is not as abundant as chlorophyll a, and merely help in increasing the absorption range.
No matter the type of light, if you can find the exact specs for its lumens/FLUX per square foot (or the equivalent PAR for red/blue only LEDs) you can use this as a loose guide as to what you need as minimums:
MmsSeedlings 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, or something like that, lol. 8,000 - 12,000 lumens is supposed to be about the average power of the full sun without any overcast or no clouds depending on altitude and potentially other factors.
It’s not ideal, but you can make do with 2,000 lumens for an entire grow if necessary.
Writen by. MacGyverStoner Science Officer