Yarrow use seed.
With others give up on using water most of the time it will not work............get a container of rootone or some other rooting hormone. Apply rooting hormonne... stick in well drained soil & mist cuttings your success will greatly increase.

Regarding the use of Rootone and potting mix..I have done that. I was just curious if they would root in water. In Fact, I need to go outside and move those cuttings that I took this morning, out of the sun and put them in the shade. The humidity was getting the best of me after 3 hrs. outside this am, so I didn't think to put them in the shade. Hope they aren't fried!

I've done it both ways (water and soil) They will root in water, which I found out accidentally when I was cutting back an overgrown container - I randomly put the "cuttings" in a cup because it was handy, then forgot about it and left it outside, it rained a few days later and when I 'found' the cup again about 1/2 of them had roots. But I usually get better plants when I take cuttings on purpose (hehe) and stick 'em in potting soil. You don't even need to use Rootone and/or cover them, they grow like crazy - a lot of people in OK call them "weeds" because they pop up in the middle of lawns and flowerbeds and don't flower (I don't really know why but it seems like when they reseed, only a few of the new plants actually flower). Have you tried Blue Daze (evolvus)? It's another one that's pretty easy, it will root in water but the ones I root in soil seem to flower faster (I do have to use Rootone with Blue Daze though)

I prefer to root in soil. The roots are much stronger than water roots. Although several things like coleus root very quickly in water.