Let There Be Light

Elbourne(8b)January 13, 2014

I have a few questions about artificial light.

What kind of light is best for seedlings and young plants? incandescent, florescent tube shop lights, CFLs, halogen, LED, etc? Does it really matter?

Are there rules of thumb about how much light, i.e. candle strength and wattage?

Can they take 24/7 of light, or is some dark necessary? If yes, how much and why?

Thank you for reporting this comment. Undo

You can probably use any of the various types of lights. You will see posts on hear using them all. Most starting out just go with the simple on lower cost 4 foot shop lights. They give good even, relatively efficient lighting and cover a large area. They can be placed side by side to create an even larger footprint.
I suggest the T-8 lamps as they are more fuel efficient and put out more light than T-12's. T-5's are even better but they are more expensive usually. T-8's are 32W, where T-12's are 40W however, that is power usage and not light output. The T-8's will actually usually be higher lumen output while using less power. Again, the T-5s are even better but more expensive.
Bulbs should be in the 4500K to 6500K spectrum for plant growth. They are normally labeled as "Daylight" bulbs. I don't really care for "Grow" bulbs as they are labeled. They cost more and put out less lumens usually and are normally not in the upper half of the light spectrum that plants really like.

Some people run 24 lights for the first few weeks after seedlings come up and then start cutting it back slowly. I just run 12 on 12 off most of the time until they get outside. I might run them longer the first week or two after they sprout.

You can spend the money for some of the other light technology, but it can get expensive. To start with, I suggest the shop lights with t8 bulbs. It is about as inexpensive starting out as you will find and it works. Then, if you decide after a year or two to quit, there are still tons of uses for those lights. Unlike a bunch of other LED or specialty light setups.

Here is my setup that I have used the last three seasons and will again this year. This shows two banks of 4 foot shop lights and was taken in 2012. Last year, I added a third bank. The PVC pipe frame allows me to adjust them up and down and side to side as needed.
Oh, and you want to keep the lights as close to the plants as possible without touching....about an inch is good. Unless you use incandescent bulbs or other high heat producing bulbs as you might cook them.

This post was edited by esox07 on Mon, Jan 13, 14 at 14:57

    Bookmark   January 13, 2014 at 2:54PM
Thank you for reporting this comment. Undo

Good set-up. I usually run two "warm" and two "cool" spectrum bulbs 12/12 too. They're in the GH, so they get some solar exposure during the day when it's not cloudy.

    Bookmark   January 13, 2014 at 3:54PM
Thank you for reporting this comment. Undo

Yep, I have seen several members post that they use the more medium spectrum bulbs exclusively or in conjunction with the higher spectrum bulbs. I have tried the combo setup but prefer the 6500K bulbs. Sunlight is definitely preferred though even if it is indirect.

    Bookmark   January 13, 2014 at 4:19PM
Thank you for reporting this comment. Undo

Never use incandescent they will do u no good. I use the 4' shop lights with the absolute cheapest bulbs I can find, it doesn't matter what kind to me as long as they are the cheapest. I put the actual tubes an inch or less from the plants. If you are just growing seedlings to eventually plant outside you can't beat fluorescent lighting. When this setup is in full swing I have thousands of pepper seedlings under the light. It works great for me

    Bookmark   January 13, 2014 at 9:15PM
Thank you for reporting this comment. Undo

I'd say it depends on how you define "best". But, that aside, the 4' fluorescent "shop lights" are probably the most commonly used. I'm not sure, but, I think halogen would be a very bad choice due to the heat. You want the lights inches away from the lights (with the floro's). Light falls off exponentially with distance. If you're not going to have very many / space is an issue, you can get a lot of CFL's in a small space. I don't know much about LED's, particularly the newer LED bulbs.

    Bookmark   January 13, 2014 at 10:23PM
Thank you for reporting this comment. Undo
seysonn(8a WA/HZ 1)

I have same set up as Bruce. Mine take T8 tubes. It is very economical. each unit (with 2 bulbs) all together costs about 20 bucks.
The advantage of fluorescent shop light is that they can be aimed at your seedling, at a close distance, evenly, giving you a big bang for the buck.

I use 6500k bulbs. I think they are closest to the more expensive grow bulbs. My seedlings all stay short and stocky, just like commercially grown seedlings. The trick s, as Bruce mentioned, you need to have the light very close to the seedlings, almost touching. Since they run cool, there is no danger of burning the seedlings.

    Bookmark   January 14, 2014 at 12:42AM
Thank you for reporting this comment. Undo

I rigged up my grow area this morning. I had a shop light and wrapped the space with plastic. Since the florescent tubes do not put out any heat, I'm considering a couple of heat options. I have a small space heater I could put on low under there, but even that might get too hot. One incandescent bulb might do it, since this is in my garage and it doesn't get all that cold here. Or I was thinking, I have an old crock pot I could fill with water and keep on low, which I guess would raise the humitidy, which is good; right?

What is the best temp for germination?

    Bookmark   January 14, 2014 at 12:22PM
Thank you for reporting this comment. Undo

Yah, that humidity with the crock pot would be a plus. Just might not be real efficient energy wise...probably an incandescent bulb would be better in that regard.

    Bookmark   January 14, 2014 at 1:21PM
Thank you for reporting this comment. Undo
seysonn(8a WA/HZ 1)

Elbourne, How cold is it in your garage ?
They say that 55F - 65F is a good temp range for seedlings to grow at a slow paste. But then if you want them to grow faster, higher temps can be better. In a small confined area an incandescent bulb cant heat it up nicely. Before I bought my heating mat (rather heating pad) I was germinating on the top of a lamp shade, using one of those fluorescent bulbs. The temperature up there could get up to 100F.

    Bookmark   January 14, 2014 at 2:03PM
Thank you for reporting this comment. Undo

Our temps range from mid-60s down into the 30s this time of year. My garage has no insulation, so its about whatever the outside temperature is. It was probably about 60 today. I put a light bulb under the plastic earlier and I'm about to go check it now.

We did have a crazy cold snap last week and we got down to a record 18F. I can't imagine we will be anywhere close to that again this year.

    Bookmark   January 14, 2014 at 4:55PM
Thank you for reporting this comment. Undo

Its about 70F in my little contraption now.

    Bookmark   January 14, 2014 at 5:14PM
Thank you for reporting this comment. Undo
DMForcier(8 DFW)

If the garage has a concrete slab floor, then there is a healthy amount of heat radiation even at 18F that should keep the temps up above freezing for a while - it depends totally on how well sealed the building is against drafts. If it is well sealed then any little space heater can keep the temp up.

You don't want to run 24/7. Give them at least 6 hours of dark. Last year I just turned the lights out when I went to bed and back on with the morning coffee. Of course, I also had a south facing window, though with very little direct sun. Little devils did very well indeed.


    Bookmark   January 14, 2014 at 6:08PM
Thank you for reporting this comment. Undo

For germination, 80-88F is best. Annuums maybe a tad lower. But nothing over 90F and nothing lower than 70, I would say. After germination, lower temps are fine, but the closer to 80 or so, the better.

I'm with everybody else, T8' "daylight" no more than an inch above the tops.. Actually, if it's not too cool in your garage, the minimal heat that fluoros do put off is just about right without any supplemental warmth.

So, what I did this past year was run my lights all through the night and in the morning when temps were cooler...In the afternoon and evening, when ambient temps were warmer, they were off for about 8 hours.


    Bookmark   January 15, 2014 at 2:22AM
Thank you for reporting this comment. Undo

I do have a concrete floor, but the garage is not sealed at all. Just hardiplank siding on the studs. My "garage" is actually just the space under my elevated house that sits 12' above grade. We live on the gulf coast

It was 60F in my germination box this morning with a temp outside of about 40F. I think I am going to lay a piece of foam board insulation over the top to hold in a little more heat.

I did not have time to plant last night. It is supposed to freeze again this weekend, so I might wait to plant until next week.

Once they start sprouting, I have some cola crates to raise the pans up closer to the light.

btw, the good folks at http://pepperlover.com/ sent me a lot more seeds than I ordered. So I think I'm going to have to build a bigger box, find more lights, and make more space in the garden. :)

    Bookmark   January 15, 2014 at 9:20AM
Sign Up to comment
More Discussions
Lemon Peppers
I grew these last year from store bought seeds. They...
Seed soak
IIs 24 hours too long? I won't be home until then....
Need advice on how to suspend shop lights.
So I bought the below metal shelving to house seedling...
Your Grow List --- 2015
It is getting closer to start the season especially...
Seysonn_ 7b-WA/HZ1
Do Habs take longer to germinate?
I've only had one Hab germinate after 2 weeks and almost...
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™