Joyce, the best time to root hib cuttings is in spring. I know it's difficult waiting, lol, but to get best results you should wait.
I fertilize my hibs w/a speical hib food ever 3 months throughout the yr..as long as there's good light, there's no reason not to fertilize..Now if your garage is dark then I'd withhold feeding.
My hibs are growing in se windows and artificial lighting at night.
BTW, do you know if your friends hib is a tropical or hardy hib? Toni

Toni, Thanks for the info. I don't know if the plant is tropical or hardy. I didn't buy it and the person threw away all info. She did say that the seller told her it would not come back next spring on its own so I figure it is tropical. It has beautiful yellow flowers with a red stem in the middle. That's why I'm trying so hard to save part of it. My garage is not heated and does not have a light at night. I do have it placed near a south window.

For tropical hibiscus, see
http://trop-hibiscus.com/gindr.html