the longer you wait the worse, im pretty sure i remember reading that after about two weeks you wont have that much success, but it always worth trying with the bottom branches that never get much bud formation anyway.
I've only done it twice, but the last time I did it, she was 4 weeks in. And for some reason, they rooted the fastest I've done yet, 1 week. But I'm sure u can do it even later than that with no probs. CH
Also keep the cutting to a minimum as it will stress out a plant in flower....you might see a slight delay in growth. I've done almost a month with no problems rooting but it takes them a while to revert to veg,
Ive taken clones from my plants 2 weeks into flower and they rooted a little slower than my other clones but they still rooted. So its not the best idea but if you need some clones and have no choice it can be done.
no i need them cause at end of may ill be on my 2nd veg cycle here and i have clones for that but im also staring another grow in a 50 sq foot area using 3 600 watt hps figure ill put 12-14 in there