Keep Your Mums Alive Over Winter: A Guide to Hardy Chrysanthemums

What Are Hardy Garden Mums?

Which mums are NOT perennials: Those greenhouse-raised florist mums have been pampered, pinched, and pruned into tightly packed balls full of buds ready to burst forth into bloom. 

They’re perfect for your yearly fall decorations, but I have learned the hard way that the chances are good they will not be making a repeat performance for you next year.

I’ve tried all the tricks pitched by the experts:

• “Get them in the ground as soon as possible so their roots have a chance to get established.” Dead!
• “Plant them in a protected microclimate area in your yard.” Deceased!
• “Mulch them really well with straw, leaves, and boughs of evergreen.” Departed!
• “Don’t cut them back until spring.” Still dead!

Those tricks might work if you are in a warmer part of the country, but none of them work otherwise.

You must choose a “hardy” garden mum and not a florist mum, which are annual decorative flowers.

Unfortunately, to grow reliably perennial mums, you need to plan ahead and look for hardy garden mums when shopping for plants in the spring.

Read our article on “Are Mums Perennials? Which Mums Come Back Year After Year.”

Types of Perennial Mums to Try

I had never heard of hardy mums until my partner Tom bought seeds one year, and we gave them a try. They blossomed the first year and have never faltered—even with no extra winter protection. Tough as nails and just as beautiful as the showy ones!

 Ours hail from Korea, but there are some varieties that are native to Siberia—talk about hardy! You may be familiar with the Korean ‘Sheffield’. It is a reliably hardy single pink daisy-like flower with a yellow eye. Bred in Connecticut, it has been around for years. 

Some other named Korean varieties are lavender ‘Venus’, ‘Red October’, amber ‘Bronze Elegans’, and rosy ‘Mei-Kyo’, which is very compact and needs no pinching. 

The University of Minnesota has been breeding mums for cold hardiness and ornamental value for years. They have developed several series of plants that are hardy to Zone 3, including:

• Compact cushion mums that grow to be 12 to 18 inches tall and
• Mammoth shrub mums that grow 3 feet tall and spread 4 feet in width, along with traditional upright mums.
• The Morden Mum series from Canada is also hardy to Zone 3. If you find a mum with Morden in its name, you know it will be reliable. 

Planting Hardy Mums for Best Growth

Zones 4 through 9

Plant hardy garden mums in the spring so they have all summer to get established. They like rich soil high in organic matter. Good drainage is essential; a soggy location will cause the roots to rot. They need at least 6 hours of sun to bloom well and not get leggy.

If you do not plant your hardy mums in the spring, you can plant them in the fall, but get them in the ground no later than mid-October in most areas (preferably earlier). They need time to establish roots. You’ll be amazed at how much the mums grow in the ground versus in a pot.

Zones 3 and Colder

If you live in zones colder than Zone 4, or it’s late autumn, your best bet is to overwinter your potted mums indoors in a cold, dark place. Here’s how:

• If the plants are in the ground, pot them up after the first fall frost; include as much root system as possible.
• Leave the foliage on the plants.
• Water well and place in a protected area where it is totally dark and 32º to 50ºF. An unheated basement or a dark, cold closet works well. The plants will hibernate for the winter as long as you keep their roots from drying out.
• Check pots weekly and water enough to keep the soil lightly moist; remember that they won’t be using much water while hibernating, so be careful not to overdo it!
• In the spring, acclimate plants to light gradually and set them out in the garden after the last killing frost. Cut down the old leaves and stems once you see new foliage emerge.

With a bit of forethought and care, you can keep your mums blooming year after year! 

Pinching and Care Tips for Maximum Blooms

For a compact plant with more flowers, pinch back the top few inches several times over the spring and early summer, or wait and cut it back by half in late June or early July. (See our story on the Chelsea Chop.) 

Day-length sensitive, they start to form buds in late summer when nights get longer. Nighttime lights can throw them off, so you should not plant them near security or street lights that could disrupt bud formation. 

Want to read more about mums? Check out our Growing Guide for Chrysanthemums for growing and care tips.