Jennifer Schultz Nelson
Extension Educator, Horticulture
I used to think of chrysanthemums as a hardy perennial planted in the fall. My mom used to have a mum that was in our garden as long as I could remember. It was so reliably hardy, I grew up thinking all mums must be hardy. When a particularly cold winter wiped out even this super-hardy mum, I thought that we could replace it without a problem. Boy was I wrong! Several plants later, we still haven't found a plant to match "old reliable". It is really not surprising considering the genetic diversity among chrysanthemums.
There are many different varieties of mums out there. Based on flower form alone, there are 13 different classes. Each of those classes contains dozens of varieties. Not only do the flower shapes differ, but so do countless other traits, such as flower color, plant height, leaf shape, and importantly, hardiness. With so many varieties available, plant breeders routinely cross varieties with each other in hopes of generating a new flower that everyone "has" to have. As a result, hardiness does vary a great deal among chrysanthemums.
There are several ways to stack the deck in favor of a chrysanthemum surviving the winter. The obvious choice is to plant in a sheltered location, usually close to the house or other structure on the property. Another often overlooked strategy is to plant in the spring. This gives the plant ample opportunity to develop an extensive root system which will help it survive the winter.
Planting in the spring does bring with it some extra duties to insure a great flower display in the fall. Mums need to have the growing tip pinched out periodically or they tend to become long, leggy, and fall over. Pinching encourages a compact bushy form, but pinching should only be done until mid-July since after this time the plant begins to form flower buds. The lengthening nights of late summer trigger flower bud formation.