Light change during veg

(copypasta from another post in the newbie thread)

I have a question regarding light changes during veg... I started an indoor grow, 400w HPS / top-drip hydro system using hydroton / GHE 3-part nutes, etc. and I have about 2 weeks of veg left. I started vegging under HPS because that's all I had at the time, though I just got a couple of 400w MH bulbs. My question is - can I switch bulbs (and color spectrum) now, with 2 weeks of veg left, or should I stick to HPS till harvest ? My girls had some heat stress in the beginning, and though I sorted the problem out I don't want to stress them out more with a light change in case they hermie.

Would they handle the stress if any?
Would they benefit from just 2 / 3 weeks under MH before going back to HPS?

Thanks in advance for your infos.

Peace,
 

reddan1981

Well-Known Member
you could also keep the mh on throughout stretch to shorten internode length. My opinion is, leave it with the hps ( it is mixed spectrum?) Too often we faff, its better to set it.... Then let her do her thing.
 

hyroot

Well-Known Member
switching bulbs, there's a spectral transitions. Slowing growth for a week while the plant adapts. Imo its best to be using the same light in veg and flower. If changing lighting. Change the bulb or light when there's 2 weeks left of veg. So there's no spectral transition when flipping to 12/12.
 

Lysergicpt

Well-Known Member
if your HPS is not Dual spectrum , i would suggest you switch it to MH for a better Vegging and get a dual Specturm for flowering , your plants will thank you cause they can benefit from the blue specturm during flowering it is proven that it increases THC production due to more UVB output , if your hps is dual spectrum , just leave it , next grow start with the MH from the beggining.
 
Thanks for your replies, so I think that as long as there is growth I won't fiddle. By dual spectrum I take it you mean a HPS that puts out at around 4000k ? My HPS is 2100k and my new MH is 6400k.
 
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