Plant distance from light

jimbo53 · Jan 25, 2015

Anyone have a good rule of thumb for the distance a plant will be happiest away from the light source?

These are (6) [100 watt 6500k 1600 lumens] CFLs and the grow box is approximately 15 sq. ft.

The plants are drying out really fast and the cups (soil) is really warm using this distance and setup.

Any advice would be greatly appreciated.

meinchoh · Jan 25, 2015

CFL's will not put out much heat at all, so as close as possible. Too far away and the seedlings will become leggy.

moruga welder · Jan 25, 2015

agreed , the closer the better . put your hand above the plants if the light burns your hand or to hot move it up a little , i keep my fan on the whole time my lights are on blowing straight across the bulbs . blows heat away .

jimbo53 · Jan 25, 2015

Meinchoh and Moruga Welder, thanks for the info. It gets very warm and dry in there, I am having to leave my front flap almost half way open even with the side vents I cut out. I also need to find a way to add a little moisture in there, may be some damp sponges or something. Its like a very dry heat, when I hold the cups they feel very warm. I'm scared I might be cooking the little fellows. That is why I was wondering how far away from the light (heat) source I could get away with and not make leggy.
My fan is set up to come on when the light do.

D3monic · Jan 25, 2015

hang a gauge about an inch above the plants, I use wireless ones so I don't have to go to the grow room to check.http://www.wayfair.com/Lacrosse-Technology-Wireless-LCD-Thermometer-Wall-Clock-WS9160UITCBP-L1563-K~LCTG1026.html?refid=GX50899259460-LCTG1026&device=c&ptid=83323765879&gclid=CjwKEAiAxZKmBRD_5cCvs8SbxXsSJADZBCmddxZ281veD4B9iNQudAxUTVwNklLm1obcg_id1mS0sRoCKK_w_wcB

Also they look to be sitting on a metal pan. That could be conducting heat from the lights and baking to root zone.

jimbo53 · Jan 25, 2015

D3monic said:
hang a gauge about an inch above the plants, I use wireless ones so I don't have to go to the grow room to check

Also they look to be sitting on a metal pan. That could be conducting heat from the lights and baking to root zone.

Thanks D3monic, I have digital instant read thermometer I use for Smoking, with a wired probe I can put in the soil in the grow box and hang the display on the out side.

Also, yes that is an aluminum baking sheet I have them sitting in, i was going to use it to bottom water, never thought about it being a literal heat conductor. But it makes since, thanks.

moruga welder · Jan 25, 2015

leave a end open , i have a 4x8 mylar grow room and i don't sip up the middles . 80 degrees with lights on and 74 when off , i leave the grow room door open some . we to have dry heat ( forced air ) but go ahead leave a open end .

you can leave a end open , hang a piece of mylar fold in half ,

Geonerd · Jan 26, 2015

FWIW, I have some seedlings growing about 3 inches from standard 100 watt equivalent CFL bulbs. IMO, the light your rig produces shouldn't come anywhere near damaging the plants. If anything, consider adding a few more bulbs!

Do add ventilation. Keeping the plants and soil around 80~85 F is close to the sweet spot.

Swampy_NZ · Jan 27, 2015

I hung a small wet hand towel from a coathanger in with my plants that helped with the humidity.Just wet it when it dries out.

hot stuff · Jan 27, 2015

Put your hand over the seedlings and move the light to where you just feel thd heat from the light then back it up a little . Continue to move the light in same fashion as seedlings grow.

Jamison · Jan 27, 2015

moruga welder said:
leave a end open , i have a 4x8 mylar grow room and i don't sip up the middles . 80 degrees with lights on and 74 when off , i leave the grow room door open some . we to have dry heat ( forced air ) but go ahead leave a open end .

you can leave a end open , hang a piece of mylar fold in half ,

IMG_0056.JPG

Love your reflector on the far left there!

moruga welder · Jan 27, 2015

hey thank ya Jamison lol ! i've 5 more domes out in the garage but to lazy to change over , did that one last grow . got them domes from work , e39 sockets just threw some 18,000 lumen sun god cfl's and away they go ! :onfire:

jimbo53 · Jan 27, 2015

Hey Guys thanks for all the help.

Swampy_NZ said:
I hung a small wet hand towel from a coathanger in with my plants that helped with the humidity.Just wet it when it dries out.

Thanks swampy I'll have to give this a try

Geonerd said:
FWIW, I have some seedlings growing about 3 inches from standard 100 watt equivalent CFL bulbs. IMO, the light your rig produces shouldn't come anywhere near damaging the plants. If anything, consider adding a few more bulbs!

Do add ventilation. Keeping the plants and soil around 80~85 F is close to the sweet spot.

Geonerd, I put my thermometer about 3 inches from the lights and it read 92 degrees when the lights were on and got down to 68 when lights were off. Will need to work on more ventilation. The temperature in my garage is not very stable. Neither is the temps outside right now got down 39 last night and up to 81 today. Got to love South Louisiana Weather.

moruga welder said:
leave a end open , i have a 4x8 mylar grow room and i don't sip up the middles . 80 degrees with lights on and 74 when off , i leave the grow room door open some . we to have dry heat ( forced air ) but go ahead leave a open end .

you can leave a end open , hang a piece of mylar fold in half ,

IMG_0056.JPG

Thanks Moruga I folded over both corners a little more today and got the temps a little more in check.

hot stuff said:
Continue to move the light in same fashion as seedlings grow.

Thanks hot stuff, I'm having to work things a little backwards at the moment due to my plants all being different heights; so some are on the bottom while most or on different size make shift stands.