I usually take what my brother-in-law referred to as Irishman's cuttings. In the backend when flowering is over I cut the chrysanthemums right back to about two inches and lift the stools and put them in the cold frame to over winter. In Spring there will be a number of shoots that start to grow fom the base of the stool. With care these can be broken off along with a piece of root and will grow very readily. Watch out for slugs! If you don't keep a careful eye on the chysants the slugs will eat off the new shoots in the cold frame before you are aware that the shoots have started to grow.