Harvest Dilemma?

I have an Indica and Sativa strain this grow. I have not grown the Sativa before but it appears it is going to take 2-3 weeks longer to mature. Because of this and space issues I'm trying to figure out how I can take the Indica's into 36 hours dark before harvest. I need to keep the lights 12/12 on the Sativas. Any ideas on how the Indica's could be put into dark for those additional 12 hours while completing the Sativa's? Kind of a dumb question. Maybe figure out a way to cover them in makeshift area with black plastic? Cover with large black garbage bags (or will this create problem with ventilation)? Any suggestions would be helpful but I don't want to do anything that would hurt the plants. Pics show the Indica strain that effectively have one large Kola per plant.

Create a darkroom like you said with a filtered fan blowing in. This will prevent mold from forming which is an issue

Good luck

bamboo sticks and pillow cases with the fan,make a teepee...kinda thing,lets air in the bottom ,no light in on the plant....B

stick em in a closet, its not like its goin to kill em.if odor is a problem, place in box with plenty holes placed in grow room....peace