If you had to choose

[Veronis]

Let's say you have one pot with VFT seeds, and you have to pick between using...

one of these:

http://www.1000bulbs.com/150-to-200-Watt-Compact-Fluorscent/33999/

or one of these:

http://www.1000bulbs.com/105-Watt-Compact-Fluorescent/31681/

Which would you pick?

I'm most curious about trading 6500K for 5000K, vs. trading 10K lumens for 5K lumens.

At my current level of understanding, I would pick the 105-watt CFL because of the 6500K color temp. My understanding of the importance of lumens for VFT's is that while important, color temp is more important...right, wrong?

 

[Goldslinger]

Go with the 6,500K; the plant can utilize nearly 100% of that area of spektrum. Lumens are how bright it is to Human Eyes.

6,500 may not seem too bright to us, but it is blazing to a plant. Temperature (Kelvin) is very important to get the most out of the wattage.

 

[GregNY]

Also take note of the base of each of those bulbs. The 5000k bulb is mogul based, which you probably dont have a fixture to house such a bulb. I would think that 6500k would work out...

Found this for you, just a bit cheaper - http://www.growlightsupply.com/105-watt-cfl-grow-lamp-6500k-p-83.html?utm_campaign=export_feed&utm_medium=cse&utm_source=googlebase&m1track=googlebase

 

[cp-connection]

Definitely go for the higher lumens. To give you a reference point a 4ft t5 bulb is 5,000 lumens. Many fixtures have 4 or more bulbs.

Think of higher Kelvin (5K+) as spring time colors that encourage leaves and lower (3k range) as summer colors that encourage flowering. Plants can only use the visible light spectrum for photosynthesis but use the different colors of light to know what time of year it is.

The two bulbs you're looking at are both in the white/blue looking end of things and will be fine for growing your junk!

 

[Nickrober]

will be fine for growing your junk!

JUNK?! Not junk, awesome plants!