Controversy over MJ book about light distance

[Griffon]

I was reading in my book to keep compact florescencts 12-18 inches away from seedlings for best growth and HID light 3-4 feet away for best growth. I am at my maximum distance with my metal halide system and I am only a foot away.

I read through many posts on this forum and I remember someone saying to keep the lights as close to the tops of plants at all times. The rule of thumb was to put your hand just above the plants and hold it there for 15 seconds 20 seconds. If you can without burning yourself the height is ok. If you can't increase the distance. Is this a rule of thumb i should be using in this stage of growth? Do you think the distance is good for my setup? My grow room is about 22 inches wide and 15 inches deep. I am using a 175 watt system. Air temp is usually around 80 degrees. Humidity 40%

I do want my plants to be as short as possible, I don't want to put the lights too close though, this is my first grow so I'm not sure. Also, I am planning on moving them for flowering. They will be in a slightly taller area 2.5 feet. (REALLY short isn't that?!) I'm starting to think my little personal grow might not work out after all

 

[NYC_Diesel x Jack_Herer]

three letters....LST

Do a search, you have enough space. Flower them while still very small and start training them sideways. Another option would be a SCROG. Keeping your lights 3-4 feet away is a HORREDNOUSLY bad idea. Man made lights are not like sunlight. The power of a grow light decreses by a factor of FOUR as distance doubles. If a plant one foot from your light is getting 5,000 lumens, a plant two feet from the light is getting 1,250 lumens, and a plant 4 feet away is getting only 312.5 lumens!!!!!!!!

 

[Growdude]

For seedlings your fine at 3-4 feet with a HID light, closer if its not to hot.

Do you have more vertical room when it comes time to flower?

I run my lights as close as I can without burning them.

 

[Friend-of-a-friend]

yup, close as you can get em w/out burnin ems best.

 

[WeedHopper]

The closer the less strecth ya get.

 

[LassChance]

yup, close as you can get em w/out burnin ems best.

I agree that LSTing or JOGing is your only hope in so short a space. Get them bad girls growing horizontally--and close to the light. The Gurus say that forcing the horizontal growth redistributes the plants growth hormones, encouraging the side branches to really take off--giving you lotsa more bud sites.

happy growing
Lass

 

[pcduck]

I would get a bigger or more fan and then put that light as close as you can to your plants, without drying them out. Do your hand method. Your lumens really decrease with each inch you move the light away. Plus I think you may need better air removal/circulation in your room if the temps get much hotter

 

[ms4ms]

right now keep the light high. I believe(can't see) you to be in the seedling stage or just past it. Let the plants grow some and gradually lower your lite. I'm sorry bbut the specs from your book do not relate to your closet or mine. The hand method works but soon your experience will tell you. read up on this board about lst if you arn't sure how to do it. green for your grow

 

[D3]

I have done it both ways & found the best way for me is to use flouro's. As soon as they sprout, I put the flouro's as close as possible, & keep then as close as I can for 2 to 3 weeks than move them to my aeroflo & 1000w light. My plants are nice & short & fat. In my opinion. HID's are too hot & intense at any distance for seedlings. You have to keep the light so high above them that the plants stretch like crazy.

 

[Daiwa13]

Tube floro's (t5,t12), set right on top of the plants for optimum Vegetative growth (short & bushy). With an hid, I like about 10-12 inches, But right now dealing with about 6 inches or less, (running out of vertical room). The buds get kinda fluffy and stringy when they get to close to the hps bulb, and some leaf curl. Try to tie them down, and gain a few inches back. Another option is SCROG, or just some training with a screen over the top.