Taller Plants for Medical Grow by Raising Lights Higher?

I have always heard that no matter what the circumstances, lights should be as close to the canopy as possible without burning or raising temperature of the canopy too much.

Currently, my HPS (with glass) system is about 14" from the canopy, with a good temperature of about 75 (no burn) - we could probably go even closer.

My colleague, however, claims that we need to raise the lights, to allow them to stretch taller, for greater yield, since we are a medical grow operation, and have a limited number of plants.

I have used the arguement that more power (closer lights) = greater yield in the end, and I have also heard that plant stretch reduces yield.

Your thoughts? Keep the lights low? Or raise them to stretch them and hope for greater yield? Any educational information would be GREATLY appreciated! Thanks!

You'd want an even canopy with the lights as close as possible. FiM, Scrog, top, get 'em bushy. Having the lights farther away will make the plants stretch, but they are wasting energy doing that and you'll likely end up with a tall, skinny plant with reduced yield

More veg time leads to more yields (light permitting), but I agree try to keep everything as bushy and close to the light as possible.

There is another aspect which you didn't mention. In addition to light intensity there is also coverage. I put my lights as close to the plants as possible and still acheive the square feel of coverage I need (upside down "V").

Regarding height and yield, have you considered doing any LST? This would increase yield and decrease height.

I'm not sure what LST is, so no, I haven't considered it. As I said, my colleague seems to believe that the taller our plants are, the greater yield we are going to get. My intuition tells me that the more lumen-power the plants get, the greater their yield will be.

Anyways, thanks for your guys help.

You won't get more yield (nodes), just more space between the nodes (stretch).

The buds form at the nodes, regardless of the height.

Wet

Can the person who told you this back it up with proof of any sort that taller plants with the lights further away yeild more? I'm guessing no. If they can im all ears but until then i think its best you take their advice with a grain of salt, if its true it shouldnt be hard to prove yet ive never seen any evidence that would support the claim.

LST = Low Stress Training. Basically, tying stalks and branches down to allow nodes to grow up, making more stalks and thus more yield with less vertical space. Takes more square footage per plant though. There are lots of threads devoted to the topic.

raising the lights is not going to increase your yield...its going to make it smaller since its not getting enough light coverage....and also...if your growing "medical" why are you worrying about yield? shouldn't quality and potency be a bigger factor.....aka..your growing for profit..not medicine.