Most mums that you buy in nurseries bloom short when you get them. If you don't plant them in the ground, you might as well chuck them. They look crappy and snails will eat them.
I had 2 mums that I bought at the Chrysanthemum booth at the LA Co Arboretum plant sale about 4 years ago. Special Mums just aren't sold in nurseries around here. Last March I searched online and found Kings Mums. kingsmums.com/ They custom root cuttings when you order them. I placed my order and in a month they sent them. I potted them into 4" pots for a month and set them into the garden in early May. I pinched them and am now getting my first blooms. I am still waiting for the fancy weird brush like ones to open.
There is a Mum show this weekend at Descanso Gardens. Maybe I'll have a bit of time to go on Sun. I'll be at the Santa Clarita Valley Rose show on Sat. I am missing a cactus show this weekend at the Arboretum and a family thing on Sat. Busy Autumn!