Chrysanthemum: In the fall, beautiful blooming tulips appear in garden centers. Unfortunately, they don’t always overwinter well here. When buying, look carefully at the tags – recently, in a “department store”, I saw chrysanthemums under a sign with the words “Around me” (they must be perennials). Further inspection revealed a label on each container that read “Not Minnesota Strong.” If it’s not strong there, it probably won’t be strong in Wisconsin. Another cause of death of mums is their intolerance to poor drainage during the winter and winter weather conditions. If rain falls on top of snow, or heavy snow melts and freezes again on top of plants, we often lose our mothers. The following techniques can increase your chances of survival.
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First, plant only in areas with good drainage. Avoid heavy clay soils and low, wet areas. Plant in areas with at least 6 hours of sun and good air circulation to help prevent diseases as well. Plant as early as possible for better establishment before winter. Another tip is to buy plants that are less root bound and smaller, as they generally grow better. If you choose larger, root-bound plants, be sure to loosen and spread the roots slightly before planting.
After transplantation and after The ground freezes, apply “winter mulch.” I recommend using double-shredded hardwood bark about 2 inches deep around the root zone to protect the plant from thaws and freezes. Mulch is to keep the ground frozen and avoid heaving. Do not “bury” the plant. Leave about one inch of space between the edge of the block and the beginning of the covered area. If you already have mulch in your garden, it’s a good idea to start and you won’t need to add more.
The final tip is to refrain from cutting your mum to the ground after the first hard freeze, as is the case with many other perennials (unless there is a lot of disease, then remove the stems). Research has shown that keeping about 12 inches of healthy stems in place protects the crown. It also protects plants from late spring frost. Leave the old stems until the new growth is a little over an inch tall and then cut it back just above the new growth in the spring.
—Lisa Johnson, Dane County horticulture instructor at the University of Wisconsin