People who enjoy gardening might make poor stand-up comedians. Gardeners chuckle at things others might not find amusing.
For example, when discussing botanical species like Hosta sieboldiana and Hosta capitata, we find it hilarious to add "Hosta la vista" to the list. And when speaking of chrysanthemums, we can’t resist mentioning, “Mum’s the word.” Not exactly knee-slapping humor, but it can bring a smile.
The word mum, of course, is short for chrysanthemum, which is hands-downs the most colorful flower of fall. The potted mums sold by retailers in autumn make eye-catching doorstep and patio displays, but mums truly shine when grown in the perennial garden.
Most blooming potted mums sold by retailers are meant to be temporary seasonal decorations, and aren’t types that are winter-hardy for our perennial gardens. Sometimes they’ll survive if planted outdoors, but often they don’t.
Some locally owned garden centers do sell blooming potted mums that are winter-hardy varieties, which is a nice plus, as they can be planted outdoors with greater chances of survival.
Mums truly shine in the perennial garden, giving vibrant color when other flowers are long gone. They even tolerate frost quite well, sometimes blooming under the first snowfall. For best success in flowerbeds, we must choose wisely, selecting varieties that are winter-hardy for zones 3 and 4.
How do we know which mums to plant in our perennial gardens? The University of Minnesota has been a leader in mum breeding, a program that started in the 1930s. Until then, there were no garden mums that were adapted to Minnesota or North Dakota’s growing conditions. The program has since released 76 mum cultivars, although some have become unavailable heirlooms.
In 1977, UMN researchers discovered a genetic trait called the “cushion” habit of mums, where the outer surfaces of a mound-shaped plant are completely covered with flowers, instead of blooms only at the tops of upright plants like previous types. The cushion habit quickly became the world’s standard for mum growth, as the university released the “Minn” series of cushion mums, including Minnautumn, Minnyellow, Minnruby and others, which remain good perennial garden choices even today.
In 1990, UMN breeders inspecting fields of seedlings observed some with unprecedented size, vigor and increased winter hardiness, which became the Mammoth Mum series. Their habit is termed “shrub cushion,” and the plants can eventually become a flowering dome-shape, 3 feet high and wide. The series includes coral, bronze, pink, lavender, red, white and yellow, in daisy and quill flower shapes.
8 steps for perennial mum success
- Choose varieties bred for our zones 3 and 4, such as the Minnesota cultivars.
- For best winter survival, begin in spring from starter plants purchased from garden centers. Mums survive best if given the entire growing season to establish before winter.
- Locate in full sun in a spot that typically receives plentiful winter snow cover. Avoid open, windswept areas.
- Fertilize generously in spring and early summer, but stop by July 4 to allow plants to toughen before fall.
- Mums will grow all summer and begin blooming when shorter days and cooler temperatures trigger flower buds.
- Leave tops intact over winter, which is vital for mum winter survival. Wait to prune off tops until the following spring as new growth emerges from soil.
- Cover with 12 inches of straw, leaves or shredded bark mulch in November after soil freezes to prevent damage from alternate freezing and thawing.
- Mums divide easily in spring, as new growth is emerging from soil level. Dig and reset vigorous clumps of new growth from the outer perimeter of last year’s plants.
Another interesting way to carry mums through winter is indoors. Small plantlets from the mum’s outer edges can be potted before frost and grown on a sunny windowsill. Cut back next spring and plant outdoors in May.
Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at firstname.lastname@example.org or call 701-241-5707.