I am pretty sure they are plants that are pruned to be tree like grown for the fall flowers.. someone correct me if i am wrong.. they are not hardy here planted in the ground...john

Many of the gnomes, cascading, or mounding types of chrysanthemums can be grown as (usually) short-lived bonsai. Most often, training begins in late summer for plants that will be shown 14-15 months later. After that, their future viability is usually uncertain, but many mums have survived for several years as bonsai. If you want precise and in depth information, try to get a copy of the out of print book "The Art of the Chrysanthemum";
by Tameji Nakajima and H. Carl Young

I'll tell you in advance: it's a LOT of work and timing of operations is critical.

Al

Ya, what he said...and...

These days there are many hardy mums to chose from as far as color goes as well. The first season you can grow them in the ground in a nice sandy soil situation. Allow a few blooms to make sure you have the true color or the color you want but pinch the rest out.

Next season you can dig early and move them into an oversized pot and continue styling until you've got it done. Then sit back and enjoy.

Bob

Styling mums for bonsai is not the result of growing on a plant for a season and then reducing it to something with a bonsai-like form and then further refining it. The technique is not a matter of carefully observing a mature mum and looking for spontaneous ideas or the 'inspiration of the moment', as in when a tree "tells" you the direction it wants you to take it; rather, bringing a believable mum bonsai into its own is the culmination of sustained effort to follow a carefully preconceived plan. Systematic attention and steps that occur over an established timetable make mums different than trees. You even need to preconceive the form (cascade, uprights, etc) you want the plant eventually take when it is still a cutting.

Generally, bonsai mums are started in small containers and are bumped up in container size and pruned on a schedule. The cuttings are usually stuck in early fall, attended/ pruned/ pinched/ potted-up for a little more than a year, and brought into their own in the autumn of the next year. Usually, that is the end of the life of the mum as a quality bonsai because few varieties lend themselves to rejuvenation as 'old-wood' bonsai, as they usually shed parts over the winter months & their form is often destroyed. Usually, most varieties don't live long enough for another design to be created from what is left. Also, most varieties die back to the ground each winter (regardless of what temp they're over-wintered at) and all that's left is basal sprouts to work with in subsequent years.

Al