Hi, So sorry this response is so late, but our Garden Doctor system has been down for the month of November and we're just catching up with questions. When shopping for mums, look for plants sold as "garden mums" because they have been developed for outdoor culture. Mums sold at florist shops as gift plants are not hardy and will generally not perform well in the garden. They are best put on the compost pile after they bloom. You can plant mums in the fall or in the spring. Keep in mind that although mums are perennials, they are not particularly long-lasting and some may die back during the winter while others do well for a few years and then disappear.