Jennifer Schultz Nelson
Extension Educator, Horticulture
One of the most common questions I'm asked this time of year is "What kind of mum should I plant that will definitely survive the winter?" I wish it was a simple answer.
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. There are approximately 30 different species in the genus Chrysanthemum. There used to be a lot more species in the genus, but as is the case in science, botanists have refined their original classifications and split the once enormous genus into several smaller ones.
Chrysanthemums are believed to have originated in China, where it was cultivated as an herb as early as 15 B.C. The flower and plant have many medicinal uses in Chinese medicine. Around 8 A.D. chrysanthemums were introduced into Japan. In both Asian nations the flower has gained great respect is symbolic of nobleness and honor.
As species, Chrysanthemum flowers aren't all that spectacular. Efforts of plant breeders are responsible for the wide range of flower color, form, and size seen today.
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.
Unfortunately, there is no way of telling whether a mum will survive the winter just by looking at it. Even those labeled as "hardy" may not survive cold winter weather.
To improve the likelihood that a mum will survive the winter, here are three useful tips:
· Plant early. Plant mums as early as possible so that their roots will grow and become established in your garden. If you can find mums to plant in the spring, they will be well-established by the time cold winds howl.
· Choose a protected location. Garden areas next to buildings, or otherwise protected spots out of the wind are your best choices.
· Use mulch. Mulching insulates roots and minimizes temperature swings that can damage tender young shoots. Do not cover the crowns until the ground freezes to discourage rodents from feeding on mums. Leave dead upper parts of plants in place until spring– it helps hold mulch in place, and offers some winter protection in itself.
When you plant mums in the spring, or when you are successful at overwintering them, this brings 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 according to several sources, pinching should only be done until mid-July since after this time the plant begins to form flower buds. I have noticed the mums in my garden forming flower buds as early as the end of June, so I stop pinching then, since I don't want to pinch out the flowers! The lengthening nights after the summer solstice in late June trigger flower bud formation.
Sometimes even when you follow every suggestion your mums still don't survive the winter. The mums I planted at my house two years ago all survived that first winter. I was feeling pretty good about my green thumb. Then last winter, with the 50 degree temperatures in January, followed by below zero temperatures, a blizzard, an early warm-up, and a week long freeze at Easter, Mother Nature reminded me who really is in charge. Those wild weather changes were enough to wake up my mums, then zap the life right out of them. Even so, I only lost two out of about twenty plants, as some still had energy to regrow though they froze back clear to the ground. Who knows what this winter has in store for us. If my mums survive, great. If they don't, I know I did all I could–the rest is up to Mother Nature.