Here’s a good article on the timing to set out chrysanthemums by the BH&G Garden Editors for Better Homes & Gardens.
Potted chrysanthemums often appear for sale at your local garden center or grocery store long before summer is over. But should you buy them yet? Find out the optimal time to set out mums to prolong their seasonal blooms.
Chrysanthemums are a favorite for outdoor fall decor, thanks to their brightly colored, bountiful blooms that cover the plants for weeks. Mums begin to pick up steam just when many other summer-flowering plants like zinnias and petunias start winding down in the cooler autumn weather. That’s why a few potted mums perched on your porch seems like a no-brainer for transitioning from summer into the next season. But don’t be in too much of a hurry if you want your plants to last. Even though retailers start selling mums well before fall begins, you may want to hold off on buying them just yet.
Remember, mums prefer cooler temperatures, which can be a problem if you buy them when they’re first available and it’s still getting to 90 degrees during the day. In the heat, the flowers will fade in only a couple of weeks so you’ll have to replace them faster if you want to keep up the colorful show. If you wait until things cool off before setting out your mums, you’ll be treated to a longer blooming cycle once you have plants in place. And should you get a few warm days here and there after cooler weather arrives, you can stash your mums in your house or garage until temps drop again.
Two other factors to consider: what type of mums you’re buying and where you want to use them. If you’re simply hoping to use mums as an annual in a potted display or garden bed, you can opt for florist (or cutting) mums. Enjoy them until the blooms die off and then compost them.
Hardy (or garden) mums are a different story. These mums are actually perennials as long as they’re properly planted and given the right care. They’re best planted in the spring once the ground is free of frost, giving them summer to establish their roots in the soil before they become knockout bloomers in the fall. If you pick up hardy mums in the fall with the intention of keeping them around until the next blooming season, consider using them in pots this year, then bring them into your home over the winter until you can plant them outside in spring.
For either type, when picking out plants at your retailer to buy, choose mums that are still budding and not in full bloom. You’ll be able to enjoy their flowers longer this way.
The bottom line is that there’s not a “best” time to put out your potted mums, but you’ll get optimal plant performance in cooler weather. Mid- to late-September is ideal if you want to love your mums for as long as possible.