Mums should ideally be planted from March through July to keep them from dying of frost over the winter. It is possible to plant them anytime from spring to fall, but the earlier they are in the ground the deeper their root systems grow, making their chances of survival much higher.
Spring mums are generally small and can be moved from the pot into the garden as soon as the frost is over and the ground is soft enough to be worked. Mums planted this early should bloom again in autumn of the same year. Mums are also available for purchase with full blooms later in the season.
Another major consideration in the planting schedule is the quality of the plant itself. Mums available in garden centers are generally hardy and have optimum longevity. Mums from florist shops, grocery and discount stores are often underdeveloped or are more fragile varieties. This makes them less than ideal candidates for garden planting. If they are intended for outside, it is best to plant them early in the season.
Flowering mums can be planted almost any time of year, but generally do not thrive in the winter. The plants can be composted after they are finished flowering, adding to the overall health of the garden.