· the best time to plant chrysanthemums, or garden mums, is in the early spring or late summer. If you get a few warm days here and there after the cool weather arrives, you can stash the mums in your house or garage until the temperatures drop again. Water deeply at intervals determined by your soil structure—frequently in porous soils, less often in heavy soils. Most gardeners purchase starter plugs or well-established nursery plants in spring or summer for reliability. This allows the plants to establish strong root systems before winter. We explain the best time to plant mums and where to plant them so they thrive. · according to the southern living garden book, you should set out young plants in early spring. · if you wait until things cool off before setting out your mums , you’ll be treated to blooms for up to eight weeks after the plants are in place. It’s a small chore that pays off big time when the mums bloom beautifully in autumn. By planting at these times, they’re more likely to survive the winter and come back even stronger the next year. They wilt quickly in hot summer temperatures, so, except for southernmost climates, late august into early september provides the ideal conditions to set out mums for an optimal bloom period. · any fall garden needs chrysanthemums, the long-lasting flowers also called mums. · mum seeds have low germination rates and require a long growing period (up to 4–5 months) to reach blooming size. The best time to plant fall mums is typically 4-6 weeks before the first frost date in your area. · mums grow and look their best when temperatures hover around 70°f.