Too tall...

My white widow plants are 59" and 63" tall . After another spurt they are only 8" away from my 400W HPS bulb , and I can't raise the light as its at the top of my grow tent already. Will my plants get burned this close?

AIRFLOW!!!!
it makes all the difference in the world. with a 400 watt you can get pretty damn close to a plant contrary to popular belief. Its all about movement of the heat. I keep my 600's roughly 6inches away from tops at times ..keep in mind i have very good airflow in my room with air cooled hoods that allows this closeness. There was a gardener on here that used a 1000 watt about 8 inches to a foot away for CLONES, jus gotta have the air/heat issues taken care of. Then theres lumen disbursment...if your plants top is that close, then its soaking up most of the light you know...To answer your direct question, given that you have your reccomendened light per square foot, and air/heat movement up to par...your plants will not get burnt 8 inches away from a 400 watt hps bulb.

Are you flowering already? I will assume you are. So the only thing you can do if you cant remove the heat with fans is to bend your plant and tie it down. If you have the room for it, you can probably increase yeild by opening the plant up to more light.

With good fans you can make it work for now but you have to assume they will keep growing, even late in flower the grow taller... Next time you better top them once or twice in Veg...

I have no idea why i naturally assumed they were in flower( i guess the strain height and the HPS), but i did, sorry that i did not not even take the veg cycle into consideration. I just wanted to apologize for missing that chunk of it, we still dont know what his issue is but on good faith i just wanted to say my bad and good eyes TheWorldIsMine...

tie the top over

the guy at my local hydro store actually showed me this new cooling system, it uses water sorta like a cool tube. the light is encased in a class cooltube and has another glass tube around that and the water flows between the 2 tubes taking all the heat. he had 2 1000W hooked up with this system and i could litterally grab the out glass tube and it was cool to the touch and almost no heat produced, plants a few inches away.

906breeder said:

I have no idea why i naturally assumed they were in flower( i guess the strain height and the HPS), but i did, sorry that i did not not even take the veg cycle into consideration. I just wanted to apologize for missing that chunk of it, we still dont know what his issue is but on good faith i just wanted to say my bad and good eyes TheWorldIsMine...

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They have been flowering for exactly a week, the white widow shot up 9 and 12 inches just lastnight. Unbeleivable!! The big bang that are only a week or so younger, from seed, are only 16 inches max. Last time I grew this they ended at 3.5 feet.
For my air-flow just now I have my TT extractor fan hooked up to my carbon filter next to my light, (bare reflector shield, no hood) and I have put 4" ducting in the side of my tent for inlet along with the vents. Maybe I should get a 4" desk fan or something and hang it next to the light?

After just checking my babies there I've come to realise something thats pritty obvious. When my tent is closed, the vacum affect created between the extraction fan and inlet flow duct will give enough circulation and stop my leaves burning. I just saw a leave start to droop due to heat when I had tent open as the hot air wasn't being forced about so much. I think I'll get a small fan still even just for feeding times.

if too close to the light, the buds can also get bleached by the light depending on the intensity. might not hurt to tie them down a little bit as well. looks ugly, but it won't hurt the plant unless you put too much stress on the branches and snap something.

tehnick said:

if too close to the light, the buds can also get bleached by the light depending on the intensity. might not hurt to tie them down a little bit as well. looks ugly, but it won't hurt the plant unless you put too much stress on the branches and snap something.

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When the flowers start to appear at the top I will tie them to the side a bit, but I cant tie them down too much cos I have other plants they would shade. Only tonight 1 has showed on 9th day flowering its a female, with a few nice white pistils among top leaves other still aint 100%, so I may still end up with only half the problem.