Try a rooting hormone

The stems need to be free of flowers and on the thick side to root well. Thin, spindly branches don't root well in my experience.

Your water should be changed every day. The cuttings should be about 2 inches long. Remove half of the leaves. Be sure that at least a pair of nodes (where the leaves were) are submerged. This and the bottom of the cutting are the most likely place for roots to emerge. Keep in a bright window but not in direct sun. Roots should appear by two weeks or sooner.

Visit the propagation forum for other rooting techniques.

F. DeBaggio

I baught 3 pots from HD, back in may. Each pot had 2 or 3 plants. So I divided them up. Now I have 7 plants that have gotten very bushy. I did one rooting,(without hormone) it worked. My stevias have not yet bloomed. If they ever do I will save the seeds.
There you go, you can propagate them by seeds too.
Probably stevia will over-winter here in GA, z8. If they do. they should be huge next year.

Thanks everyone for your feedback, appreciate it. I will try some rooting hormone and see how it goes.