Every year in the fall, I suffer a bout of mum madness when garden centers and big boxes brim with chrysanthemums. They produce lovely fall colors, but when is the best time to plant mums?
When to Plant Mums
Then I slap myself on the forehead, take a deep breath and cry “You should have planted these in May!”
People start pointing at me and make avoid-the-crazy-woman sounds to their children and spouses. I slink off to the refuge of my car or the plumbing department to avoid further embarrassment.
Why Mums Don’t Last Through Winter
Mums are hardy perennial plant best planted in the spring. Mums that are sold in garden centers in the autumn are really being treated as annuals. They are already in full bloom with beautiful autumn jewel-hued colors to decorate your house, along with autumn wreaths and gourds. Once a flower is in full bloom, it’s actually past its peak and declining. (Be sure to buy mums with lots of unopened buds so that they last longer into the fall season.)
If these plants are put in the ground from August on, most won’t make it through the winter in areas where temperatures dip into the single digits. The reason is that mums planted late in the season are near or at the flowering stage, and they don’t grow roots to sustain plants through the winter. All the energy is put into blooming. That is why mums are best planted in the spring.
Gardeners in northern states where temperatures regularly dip below zero can lose even spring-planted hardy mums to winter. You can changes the odds in your favor by leaving the dead foliage on mums and asters instead of shearing for neatness. An Iowa State University study found that unpruned plants survive at much lower temperatures than those that were pruned. Be sure to add 4 to 6 inches of mulch after the ground has frozen for more protection.
Also, potted mums from the florist or grocery store and exotics like huge football chrysanthemums, delicate spiders, and spoons don’t survive cold winters either and are not good choices for landscapes. They are not bred to be hardy; it’s their form, color and size that are prized. Think of them as disposable holiday decor, along with the pumpkins you buy.
How to Overwinter a Mum
For your fall mums to have the best chance at survival in cold areas, overwinter them in the basement or a dark, cold closet. Pot up plants after the first frost if they are in the ground; include as much root system as possible. Leave the foliage on the plants until spring. Water well and place in a protected area where it is totally dark and 32ºF to 50ºF. The plants will hibernate for the winter if you keep their roots damp. Check pots weekly. In the spring, acclimate plants to light gradually and set them out in the garden after the last killing frost.
With a bit of forethought and care, you can keep your mums blooming year after year!
See our Autumnal Equinox page for more fall-themed advice, folklore, and fun!