Light question

jmsieglaff · March 9, 2015

I have a grow light for starting seeds with a high output 4' T5 6500K 54W light bulb (not sure of lumens off hand). I have an extra 4' shop light with slots for two bulbs, so I thought I'd rig it up for some extra lights on my seedlings (never a bad idea to have more light, right?)

I bought two daylight 6500K 4' T12 bulbs (at least that is what the cardboard sleeve said): (e.g. http://www.amazon.com/Sylvania-24477.../dp/B000BO5A1Y)

Color/Finish: Daylight
Color Temperature: 6,500K
Average Lifetime: 20000 hours
Lumens (light output): 2180
CRI: 88

But when I took them out of the cardboard sleeve, one of them was actually a 3400K 4' T12 aquarium/terraium/grow bulb (e.g. http://www.amazon.com/Sylvania-24671.../dp/B000M2TX22)

Color Temperature: 3,400K
Average Lifetime: 20000 hours
Lumens (light output): 1700
CRI: 89

At first I wasn't pleased, but then I thought the mix of 6500K light and 3400K light might not be a bad thing. Any thoughts on these two bulbs for seedlings? Compared to just two 6500K bulbs?

Worth1 · March 9, 2015

The lower 3400K is more for flowering (red).
I have heard of people mixing them I have no idea how it would turn out.

So you said you had a total of 3 6500 (blue) and one 3400 right for a total of 4 lights?
If so they should be good.

Worth

jmsieglaff · March 9, 2015

No, one fixture is a single T5 bulb 6500K (a 4' purchased grow light before I knew shop lights would be just fine), it is notably brighter than the 6500K T12 bulb--so I'm guessing the lumens is a fair amount higher.

So at present I have 2 6500K and 1 3400K. My single T5 bulb has worked fine in the past, but I'm going to have a few more plants this year so I thought adding some more light wasn't going to hurt.

Ed of Somis · March 9, 2015

Funny, I was faced with the same thing because I had a 2 bulb fixture...and some extra 3400k bulbs. As W said...the lower k bulbs are good for "full spectrum" light for continuous growing/flowering. My research told me to dump the 3400k bulb and go with two 6500 bulbs. It is working out great!

Cole_Robbie · March 9, 2015

The last bulbs I bought are 4100K and work great. I don't think seedlings are that picky about spectrum.

jmsieglaff · March 10, 2015

I probably won't hassle with taking the bulb back to the store then. I've learned to check what bulb is in the box despite what box it is. I'm glad I've got the extra light, which is allowing me to start a few more tomatoes, peppers, and flowers.

March 9, 2015	#1
jmsieglaff Tomatovillian™ Join Date: Jan 2014 Location: Southern WI Posts: 2,742	Light question I have a grow light for starting seeds with a high output 4' T5 6500K 54W light bulb (not sure of lumens off hand). I have an extra 4' shop light with slots for two bulbs, so I thought I'd rig it up for some extra lights on my seedlings (never a bad idea to have more light, right?) I bought two daylight 6500K 4' T12 bulbs (at least that is what the cardboard sleeve said): (e.g. http://www.amazon.com/Sylvania-24477.../dp/B000BO5A1Y) Color/Finish: Daylight Color Temperature: 6,500K Average Lifetime: 20000 hours Lumens (light output): 2180 CRI: 88 But when I took them out of the cardboard sleeve, one of them was actually a 3400K 4' T12 aquarium/terraium/grow bulb (e.g. http://www.amazon.com/Sylvania-24671.../dp/B000M2TX22) Color Temperature: 3,400K Average Lifetime: 20000 hours Lumens (light output): 1700 CRI: 89 At first I wasn't pleased, but then I thought the mix of 6500K light and 3400K light might not be a bad thing. Any thoughts on these two bulbs for seedlings? Compared to just two 6500K bulbs?

March 9, 2015	#2
Worth1 Tomatovillian™ Join Date: Feb 2006 Location: Den of Drunken Fools Posts: 38,539	The lower 3400K is more for flowering (red). I have heard of people mixing them I have no idea how it would turn out. So you said you had a total of 3 6500 (blue) and one 3400 right for a total of 4 lights? If so they should be good. Worth

March 9, 2015	#4
Ed of Somis Tomatovillian™ Join Date: Jun 2013 Location: Somis, Ca Posts: 649	Funny, I was faced with the same thing because I had a 2 bulb fixture...and some extra 3400k bulbs. As W said...the lower k bulbs are good for "full spectrum" light for continuous growing/flowering. My research told me to dump the 3400k bulb and go with two 6500 bulbs. It is working out great!

March 9, 2015	#5
Cole_Robbie Tomatovillian™ Join Date: Jun 2012 Location: Illinois, zone 6 Posts: 8,407	The last bulbs I bought are 4100K and work great. I don't think seedlings are that picky about spectrum.

March 10, 2015	#6
jmsieglaff Tomatovillian™ Join Date: Jan 2014 Location: Southern WI Posts: 2,742	I probably won't hassle with taking the bulb back to the store then. I've learned to check what bulb is in the box despite what box it is. I'm glad I've got the extra light, which is allowing me to start a few more tomatoes, peppers, and flowers.