November 26, 2015 – Kenosha News
Question: This fall I brought several mums on sale at a local garden center. I left them in their pots on my deck. They bloomed beautifully but now I’m wondering if I can keep them for next year. They were labeled as hardy. Should I plant them in the ground or can I keep them in the garage? Do I pinch back, cut off the dried blooms or trim to the ground? Perhaps I should just toss them and start over next year. Is it too late to save these beautiful plants? – K.B. and E.M.
Answer: Chrysanthemums have been cultivated since the 8th Century in Japan. There are thousands of varieties specially developed for use as cut flowers, hardy landscape plants, and houseplants. The term “garden mum” is often used to distinguish between hardier mums for outdoor plantings versus greenhouse mums.
If at all possible plant your garden or hardy mums in the ground for best winter survival, even if you need to move snow out of the way. Proper siting is extremely important. Garden mums need rich, well-drained soil and full sun. Chrysanthemums should be planted 18 to 36 inches apart depending on the mature size of the plant.
Frost heaving in poorly drained soil is the main cause of winter death. In late fall trim off everything above ground. Mums regrow from the roots in spring. Apply three to four inches of mulch (straw, fluffy leaves, evergreen boughs) after the ground freezes, or gets very cold. Winter mulching helps keep the soil frozen decreasing frost heave and root desiccation.
If you prefer to keep your hardy mums in their container, sink them pot and all into the ground before the soil freezes. – This only works with plastic pots, other containers will break. – The ground insulates the root system. Cut back the tops and mulch as directed for in-ground plants.
Mums may get tall and leggy if not pinched back. Beginning in May, whenever a new shoot reaches 3 to 4 inches tall, it should be pinched off, leaving 2 to 3 leaves on the stem. Fertilize and pinch about once a month. Stop pinching and fertilizing in mid-July so flower buds will develop. (In my experience, some of the new hardy cultivars don’t require pinching to control size and shape, but will bloom much earlier when not pinched.)
Barb Larson is horticulture educator for the Kenosha County University of Wisconsin Extension. She holds a master’s of science in horticulture from the University of Wisconsin-Madison. If you have a plant or gardening question, email her at firstname.lastname@example.org or call 262-857-1942.