Im currently running a 400mh cooltube setup and my lights stay very close to my 2 moms I am growing out. Im growing PPP and the genetics cause it to have very close nodes. My question is if i put my HPS bulb in and raise my lamp, would that encourage stretching as to make easier to prune, healthier cuttings?
HPS doesn't cause much stretching imo. The main aspect of light that causes stretching is having a low ratio of red to far-red in the spectrum. If you can find a way to give the plants only far-red light by using perhaps some type of LED or some other bulb with a gel coating on it, in conjunction with your MH, that should do the trick. I know it's possible because I've read studies where this has been done, but I don't remember exactly what type of lighting they used to add the far-red light. Would be a fun experiment to try.
