Mum's the word: the chrysanthemum breeding program at U. of Minnesota
The chrysanthemums breeding program at the University of Minnesota is one of the oldest public sector breeding programs in the world, and the only one in North America. One of their experiment stations for mums is located in Grand Rapids, Minn., and is a definite zone 3. Beginning in the 1920s, the U of M researchers began selecting and breeding mums for early flowering. At that time there were no mums that bloomed before Minnesota's killing frosts.
The "cushion habit" of mums, a genetic discovery of Experiment Station mum breeders, was the basis for the U of M's first plant patent in 1977, called Minngopher. The plant was dome-shaped, with flowers almost completely covering the outside surface of each plant. Previous mums bloomed only at the top of long stems (upright habit). Within a decade, the cushion type became the dominant chrysanthemum plant habit worldwide. Scientists from Asia came to study at the U. They brought new mum species and brought the new breeding techniques back to their counties.
In 1990, research breeders at the U of M were inspecting a field planting and found a seedling of unprecedented size. Now these are marketed world-wide as Mammoth mums. These plants produce several thousand flowers and grow three to four feet across in the second season and thereafter. They are winter hardy, large, vigorous and easy to care for plants. During their first growing season, these mums are comparable in size to the typical potted garden mums. They grow so strongly because they develop a substantial crown with many underground rhizomes (underground shoots that may emerge with a few leaves in the fall near the main plant). The rhizomes serve the plant as a location to store energy over winter, which the plant can then use to get off to a vigorous start in the spring. Having many rhizomes also allowed many new stems to generate a fuller, denser plant. Some of the vigorous Mammoth mum breeding lines grew to 3 feet tall and 5 or more feet wide by the end of their second season.
Unlike typical mum cultivars which rely only on daylength to flower (short days/long nights) the Mammoth mums also require a cold period (vernalization) which is experienced over winter in order to flower reliably.
Lodging, the falling or bending of stems, was the second most problematic feature of the early breeding lines. The large plant size of the early hybrids, and the weight of the flowering stems caused the stem to lodge, especially in open, windy fields or from heavy rain. The U of M took care to select parents of the Mammoth mums which had relatively strong stems and seedlings that resisted lodging.
A good location for mums is one that has at least half or more a day of full sun. They like rich, well draining soil which is neutral to slightly acidic pH (about 6.0 to 7.0). Provide adequate space (3 to 4 feet apart) for Mammoth mums to grow. However if you want a solid mass or hedge, plant 1.5 to 2 feet apart. Cultivars of these mums should have the name Mammoth first and then the color name. Names as of 2007 include Mammoth: Coral Daisy, Dark Bronze Daisy, Dark Pink Daisy, Lavender Daisy, Red Daisy, Twilight Pink, White Daisy and Yellow Quill.
Small blooming mums are available in garden centers in the spring. These mums are forced in smaller pots to save space for growers packed with plant materials of all types for the spring bedding season. The short daylength necessary to trigger flowering for these mums is provided in the greenhouse by shading or if started early enough, by the naturally short days of early spring. These should be planted out only after danger of frost is past. After flowering, the spent flowers should be removed. Throughout the summer the plants will develop a strong root system and rhizomes and bloom very strong again in the fall.
If you purchase mums now get them into the ground as quickly as possible so there is opportunity for the root system and rhizomes to develop in their new location before the ground freezes. Add mulch and leave the spent flowers and foliage in place to help collect blowing leaves and snow. This will provide the crown with added insulation, especially the first season. In subsequent years the same can be done, but it should not be as critical to ensure survival.
The future of mums will include more colors and shapes of flowers. The U is developing "Wave" types. These will spread up to three feet across and remain low to the ground. They will also be ideal for hanging baskets and include a range of colors and have daisy or double blossoms.
Kyle Schulz is a Wadena County Master Gardener from Sebeka, and the regular gardening columnist for the Wadena Pioneer Journal.