Have you ever planted beautiful fall mums thinking they were hardy perennials but they never came back again? Admit it! I have!
I first fell in love with fall mums in Indiana, where they were huge, colorful, and came back to bloom every fall. My first year back in zone 4 I promptly planted fall mums and wondered what happened to them the next spring. I just assumed that all those beautiful mums the garden centers put out each fall were hardy in zone 4. I learned the hard way that most of them are not. There are thousands of varieties of Chrysanthemums with varying levels of hardiness. You just need to get the right species and variety for your needs.
In general, the mums covered with buds or already blooming that are widely available in garden centers in the fall are either not hardy or will not overwinter well. Even hardy mums will not have a chance to establish before winter so they probably won’t survive, especially if left in a container rather than in the ground. They are not annuals, but in cold zones some are considered tender or half hardy perennials, and will not return the following season. But because they are a fairly inexpensive perennial, many gardeners use them to add late season blooming where annuals and perennials have finished, and to replace spent container annuals. These mums are quite cold tolerant and will keep blooming at least until first frost if not longer. In warm regions these mums will likely return the following year. Don’t cut them back until spring, they will have a better chance of surviving winter.
To grow mums in cold and northern climates, first make sure you are selecting a mum hardy enough for your growing zone. Plant it in the SPRING!! That will give it plenty of time to become well established before winter hits. Plant your mums where they will get plenty of sunlight, minimum of a half day but a full day is best. The shortening sunlight as fall approaches is what triggers mums to bloom, so don’t confuse them by planting them where they get extended light from outdoor lighting. Plant your mums in good garden soil, well drained, and they prefer a slightly alkaline soil. It is important the soil be well drained, the roots detest being wet over winter. Fertilize your mums every three to four weeks until the buds appear. And pinch off the top inch or two of growth every three or four weeks into July to encourage dense bushy growth and tons of blooms. When your plant has finished blooming, it’s time to get it ready for winter. Do not cut the plant down to the ground until spring, it will get through winter best if the top growth traps leaves and holds snow to help insulate the roots. It is best to apply several inches of mulch around the plant after the soil freezes to protect the roots in case you don’t get much snow to insulate them. Your roots will likely still freeze, but heavy mulch, straw or evergreen branches or snow will prevent damage from frost heaves and freeze/thaw cycles. In the spring, wait for the soil to thaw and begin to warm before removing mulch and old foliage.
There are many varieties of Chrysanthemum that are hardy enough for zone 4. Canadian Breeders and the University of Minnesota have developed several varieties of hardy mums. It is important to note though, the some of those are fully hardy in zone, but bloom too late to enjoy them. Florist Mums are very late bloomers even if they are fully hardy. When searching for hardy garden mums for cold regions, be sure to look for “early bloomers” to make sure they don’t wind up blooming right before frost kills them. Here are a few of the recommended hardy varieties, but a trusted local garden center is usually your best source of information for which are hardy in your area. And hopefully they are made available in spring.
C. ‘My Favorite’ Series was developed by the University of Minnesota. Mums in the series bloom profusely and don’t need pinching. The plants get very large reaching up to four feet tall. The blooms are frost tolerant, which extends the blooming season. The My Favorite Series should be hardy to as far north as zone 3b. ‘Coral’ blooms are bright coral with a golden eye. ‘Twilight Pink’ has bright pink blooms with a golden eye. ‘White’ is a semi double daisy bloom with a yellow eye. And ‘Yellow Quill has yellow quilled petals and a yellow eye.
C. ‘Minn’ Series are early blooming cushion mums. ‘Minngopher’ is ruby red with 2 to 2 1/2” blooms. ‘Minngopher is a later bloomer, usually around September 15. ‘Minnwhite’ has 2” white blooms. And ‘Minnyellow’ has 2” lemon yellow blooms.
C. ‘Peach Centerpiece’ blooms are 4” single blooms with quilled petals. The flowers are Developed by the University of Minnesota.
C. ‘Rose Blush’ is an upright early bloomer with 2-3” mauve blooms. Developed by the University of Minnesota.
C. ‘Sesquicentennial Sun’ is a long flowering yellow double. Developed by the University of Minnesota.
C. ‘Betty-Lou’ Maximum is a button mum with 2 1/2” red blooms. It is an early bloomer with a spread of 30”. Developed by the University of Minnesota.
C. ‘Debonair’ is a dwarf mum with bright lavender pink flowers for several weeks. ‘Debonair’ grows to 1 or 2 feet high and about 1 1/2 feet wide. Hardy to zone 4 according to some sources, but be sure and ask a trusted local garden center.
C. ‘Grenadine’ is a compact early bloomer, reaching about one to two feet high.. The blooms are coral and bronze, warm weather may fade the blooms. Hardy to zone 4 according to some sources.
C. ‘Rose Grenadine’ has cherry red and rose colored blooms with lemon eyes. It reaches about two feet tall and is hardy to zone 4. This particular variety is sold by a few reliable greenhouses in zone 4, so I would hope that it can be considered fully hardy.
C. ‘Morden’ Series was developed in Canada. This series is likely among the most hardy of the mums. ’Morden Canary’ is of course a bright yellow with deep golden yellow eyes. I have seen claims that this one is hardy to zone 3a. ‘Morden Delight’ produces bright orange red flowers. ‘Morden Fiesta’ produces bright purply pink flowers. ‘Morden Garnet’ has bright deep red blooms. A Canadian nursery lists ‘Garnet’ as hardy to zone 3. And ‘Morden Cameo’ has white blooms with yellow eyes, I have seen this one sold by a Minnesota nursery that claims it is hardy to zone 3a.