LED or T5 fluorescent? Need advice!

[CAP]

Setting up a little early this year and am looking to purchase a new light. I have used T5s in the past with nothing but success. However as i expanded my setup two years ago i bought two 24" 5000k 27w LED strips and while they are super bright i'm having difficulty finding a sweet spot. Too close and they burn the ends and too far and they grow tall, not really leggy but just not short and stocky like my T5s have produced.
I am now looking at a higher end 6400k LED. Will i run into the same issues? Should i play it safe and go with what works in the older less efficient T5s? I haven't really found any info on this. Can T5s actually be superior at seed starting? I'd appreciate any input of experiences you have had on this matter. Thanks.

 

[YumYum]

I bought a 4' led shop light from walmart (5000 lumen 5000k 45w) and have been playing around with it with some test tomato plants. They are just about ready to send out the first true leaves. I have the bulbs 4.5" above the soil. They are a bit leggy at 1.5" tall. I did have one seedling curl its leaves downwards but I don't know if that means too bright or what, the others didn't.

How far away are your bulbs?
How far away are you saying is too close?

 

[Chuck]

I have been growing seedlings under two 4-foot Soft White bulbs behind south-facing sliding glass doors for 2 winters with excellent results. I keep the bulbs about 2 inches from the leaves. Even when I forget to raise the lights for a day or two there is no burning. The seedlings show no sign of legginess and are all muscular robust plants. I start all of my seeds under this cheap lighting and see no reason to change. The bulbs say they are 3000K 40 watt. IMO, the most important aspect of starting seeds is the soil temperature before and after sprouting. I find 75F-80F optimal with my growing medium.

 

[CAP]

Well i'm accustomed to keeping the fluorescents about two or three inches off the plants, and that was too close with the LED because my tomatoes and peppers started bleaching on the top leaves and i ended up using my backup outdoor starts. So this past year i started them close and after they reached about four inches i moved the light up to about six inches and they just grew too tall too fast.

The thing that confuses me is i have read how cool LEDs are but i have never burned plants until i started using one. With a T5 this never happened even when touching. I kind of think the lights i'm using (or trying to use i should say) just runs hotter than other LEDs.

 

[CAP]

I have been growing seedlings under two 4-foot Soft White bulbs behind south-facing sliding glass doors for 2 winters with excellent results. I keep the bulbs about 2 inches from the leaves. Even when I forget to raise the lights for a day or two there is no burning. The seedlings show no sign of legginess and are all muscular robust plants. I start all of my seeds under this cheap lighting and see no reason to change. The bulbs say they are 3000K 40 watt. IMO, the most important aspect of starting seeds is the soil temperature before and after sprouting. I find 75F-80F optimal with my growing medium.

Nice! Soft White bulbs are these LED?

 

[Chuck]

Well i'm accustomed to keeping the fluorescents about two or three inches off the plants, and that was too close with the LED because my tomatoes and peppers started bleaching on the top leaves and i ended up using my backup outdoor starts. So this past year i started them close and after they reached about four inches i moved the light up to about six inches and they just grew too tall too fast.

The thing that confuses me is i have read how cool LEDs are but i have never burned plants until i started using one. With a T5 this never happened even when touching. I kind of think the lights i'm using (or trying to use i should say) just runs hotter than other LEDs.

Perhaps it isn't the temperature of the bulbs but the wave length of the light that is causing the bleaching.

Nice! Soft White bulbs are these LED?

No, they are just cheap indoor home lighting fluorescent tubes, the same bulbs you would find in an office

 

[CAP]

Fluorescents, that's what i thought.

I'm not sure what the problem is but i do know i'm not putting my tomatoes and such under them this year. I guess i'll use them for companions and other short growing plants that i can keep the light higher up on.

 

[Chuck]

Fluorescents, that's what i thought.

I'm not sure what the problem is but i do know i'm not putting my tomatoes and such under them this year. I guess i'll use them for companions and other short growing plants that i can keep the light higher up on.

I have read that using Soft White is NOT what one wants for "growing" plants or as a grow light. It is best used as a seed starting light and is good until plants get 2 or 3 sets of true leaves. It has something to do with the red and blue wavelengths and seedlings need more blue than red while older plants need more red than blue.

 

[CAP]

I have read that using Soft White is NOT what one wants for "growing" plants or as a grow light. It is best used as a seed starting light and is good until plants get 2 or 3 sets of true leaves. It has something to do with the red and blue wavelengths and seedlings need more blue than red while older plants need more red than blue.

Yep, that's the way i understand it too. Daylight or blue spectrum for vegetative growth. 5000-6500 kelvin. I think what you have going for you is that south facing location more than anything. I use one to grow lettuce in all winter, but i can't set up my seed starts there.

Now that you mention it, the LEDs i'm using are full spectrum and have some red lights in it.

 

[DirtMechanic]

The peaks in this graph are peculiar as they are so close yet inside the border limits of the visible spectrum.