quick question?

[cash4hash]

How far/close should my400 hps light be to the tops of me plants ? any help welcome thnx.

cash4hash Reviewed by cash4hash on 11-19-2005. quick question? How far/close should my400 hps light be to the tops of me plants ? any help welcome thnx. :) Rating: 5

[luckydan]

I would recomend that the 400 watt light should be no more than 10 cm or 6 inches away depending on the stage of growth eg.seedling or mature plant....
happy growing......

[luckydan]

you can get it within a couple of inches if you have a fan blowing at the light....

[Zandor]

Monitor the temperature at the top of your canopy that will tell you how close you can get your light with out hurting your plants.

[latewood]

but Z, what temp do you want to see? when monitoring canopy temps?

[turtle420]

I think a good test is the hand test...

Place your hand under the light, and move it closer until it starts burning... then place your plants just a little bit lower.

You should have air circulation over your 'canopy' and/or over your plants. You might consider a sealed reflector housing... or a cool tube.

[Zandor]

but Z, what temp do you want to see? when monitoring canopy temps?

To be safe no more then 85f at most. A better temperature is 78f but there are exceptions like if you are using CO² then you need hotter temperatures 85f-88f but not in vegetation cycle for vegetation cycle you should not rise above 83f even if you are using CO². If you are in flower cycle the first 30 days you should not go over 88f period. The last 3 weeks you can bump the temperature up as long as you are using CO² to as much as 90f. Just increase the water supply because they will drink it up very fast the warmer it is.

I wish there is one set temperature that is perfect for every plant and strain but there is not. Each cycle can use a little different environment conditions. The idea it to tweak the environment to match the cycle of the plant.

This is why I don't go deep into explanations. There are many expectations you should consider but for more then 90% of the members and other people growing it just confuses them.

Yes it's a hearty plant and can survive and grow in many different environments. Yield is as much a matter of opinion as is taste. Some are happy and feel successful if they finish one plant and yield 4 oz from it. Others want the same plant to yield pounds. It's a matter of environment control, growing technique and many other things that change an average yield from a few ounces to pounds.

Now have I confused everyone

[amckean]

I'm using a 400w HPS and I red in a grow book by Mel Frank that the light should be 18" to 24" in early stage of vegative growth and I have mine at 18" and they seem to be growing fin with no stretching but at 24" it seemed to slow down growth for a week until I lowered it again.
Hope this help
Ali

[Zandor]

I'm using a 400w HPS and I red in a grow book by Mel Frank that the light should be 18" to 24" in early stage of vegative growth and I have mine at 18" and they seem to be growing fin with no stretching but at 24" it seemed to slow down growth for a week until I lowered it again.
Hope this help
Ali

Mel (the ass hole) Frank wrote his book about 30 years ago and has sense disavowed everything he wrote. Most of his conclusions have been proven inaccurate anyway. You should pick up a newer book with better information.


There are two factors to consider. Temperature is first; monitor the temperature at the average height of your plants. To close and you burn the tips to far away and you give up luminance penetration (PAR). Second is Luminance loss. Most experts are in agreement that light intensity diminishes exponentially fast.

For example:
A 400-watt MH from 0â?� to 12â?� is about the same luminance say 55000
Same light at 24â?� the luminance is now about 30000

Still good

Same light at 36â?� the luminance is now about 1200

Fan leafs block most of the light so nothing below sees enough of the light of day to do any good.

About 16â?� is average if your plants get too tall just bend them over (if you bend them over the buds get more light and grow bigger). You could crop them to keep them short and bushy you crop between the 4th & 5th node early in the vegetation state for best results.

I hope this helps

[latewood]

Z how does that distance equate for a 1000w?

Z, If using a 1000w light, but keeping temps controlled in the low 70's, is there as much need for Co2 enhancment?, or do the cooler temps keep the Co2 levels from dissapating as quickly? Or am I totally off base, because I am under impression that heat caused by the 1000w ballasts/bulbs is the reason for the lack of Co2?

turtle...having 2 good fans, 1 to oscillate, the other toprovide airflow right across the top of the canopy, like you said, this works especially well if you have AC