Chrysanthemums, or mums, have been cultivated for centuries. The colorful choices we see in garden centers each fall are hybrids of several wild species from Asia. Dendranthema x grandiflorum can be found in a wide array of colors (white, bronze, pink, yellow, lavender) and flower types (daisy, buttons, pompons and cushions).
Mums planted in the spring require some special care to look their best at blooming time. Most garden mums sold in the fall are intended for autumn color, to be discarded after bloom. There are strategies, however, to increase the mum’s chance of surviving the winter.
Plant mums in full or nearly full sun. They set buds according to the length of the day, so avoid a site where they will receive bright artificial light in the evening.
Plant mums in a rich, organic soil with plenty of moisture. Provide a slow-release fertilizer.
Don’t forget to water your mums. It’s easy to overlook fall bloomers among all the other summer flowers in the garden.
Beginning early in May, perform what is called “pinching back”. Using your fingernails or pruning shears, slightly cut back each stem to just above a node (a cluster of leaves). This will keep the plant compact and well-branched.
Follow up the first pinching with a second pinching a month later (early June), and a third a month after that (early July).
Do not pinch back any later than early July; doing so will prevent your mum from setting buds in time for a fall display before frost.
If you garden in a warmer climate, pinching can be continued for another month.
To save time, avoid pinching by cutting the mum back by 1/2 to 2/3 in mid-June. This only needs to be done once each summer.
Stop fertilizing mums by late July in a cold climate. Encouraging new growth after this point reduces chances that the plant will survive winter.
Keep the mum watered through the fall until the first hard freeze.
In a cold climate, it is best to leave the foliage standing through the winter. It will serve to protect the plant and give it a better chance of winter survival, and can be cut in the spring to make way for new growth.
Provide mulch around the plant to insulate it from winter weather.
Divide mums in the spring by digging up the whole plant and separating the outsides of the rootball from the center. Discard the center material and replant the healthy root growth. Chrysanthemums respond well to division every other year or even every year.