Keep these beautiful fall bloomers looking their best by avoiding these no-nos. Plus, use these tips for adding potted mums to your garden.

By BH&G Garden Editors
Updated September 08, 2020
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Mums are most often thought of as seasonal potted plants, something to place on the porch to celebrate fall. But once the flowers fade, the plants wind up in the compost bin. Hardy mums (also known as garden mums) like the Igloo varieties and ‘Sheffield Pink’, however, are tough enough to survive winters as far north as Zone 4. With the right care throughout the year, they’ll put on a colorful show each autumn. Generally, mums bloom from September through November (when the days grow shorter and the weather cools off) and stay vibrant for weeks. If you plant hardy mums in your garden, steer clear of these common mistakes and you'll be able to enjoy their beautiful fall flowers for years to come.

Credit: William N. Hopkins

Mistake 1: Planting Hardy Mums in Fall

Even though you'll start seeing mums in garden centers in late summer, if you plant them at that time of year or later, it's unlikely they'll survive the winter. You'll have more success when you plant hardy mums in spring after the last frost to give roots a chance to grow enough before the colder months. Place them in well-drained soil in a sunny spot. They prefer a soil pH slightly on the acidic side, so performing a soil test will help you determine if you need to adjust the pH. Once planted, water once a week through fall.

Test Garden Tip: Local chapters of the National Chrysanthemum Society often hold spring sales where you can find interesting varieties at the best time to plant them.

Mistake 2: Not Preparing Your Mums for Winter

As soon as the first hard frost occurs in your garden in fall, it's time to get your mums ready for winter. Don't cut away the faded flowers and foliage; removing them may stimulate new growth that wouldn’t survive a freeze. Instead, make sure you protect their shallow roots with at least a 3-inch-thick layer of shredded leaves or hardwood mulch around the plant's base. This will help insulate the soil, ensuring that it remains a constant temperature instead of freezing and thawing and freezing again. All those temperature swings can stress the plants, and even heave them right out of the ground, so the more you can protect them from this, the better.

What about the potted mums you can buy already blooming in autumn? Try overwintering them indoors. First, cut off the stems at pot level, then place the pots in a cool dark area, like a basement or unheated garage. Water about once a week, just to keep the roots from completely drying out. The plants will go dormant until spring when you can set them outside again once temperatures stay above freezing.

Mistake 3: Pruning at the Wrong Time of Year

The best time to prune hardy mums is in spring, to help encourage new growth. If you prune in fall, the new stems that grow probably won't be strong enough to survive the winter. After temperatures remain above freezing, use sharp pruners to cut off last year’s stems at soil level. Remove mulch around plants and add a little 10-10-10 fertilizer or a big helping of compost to fuel new growth. While the plants start growing, be sure to keep the soil moderately moist and be sure that the bed stays weed-free.

If you stowed away your potted mums indoors for the winter, gradually start exposing your plants to light before planting them outdoors. Once planted, water and feed as you would other mums in your garden.

Mistake 4: Not Trimming Back Mums in Summer

Almost as important as giving them a spring trim, mums benefit from being cut back to about half their height (go ahead, use hedge shears) around the Fourth of July. This will prevent them from getting lanky and flopping over. If you’ve planted one of the Igloo series, wait until after its first bloom to trim, then enjoy its second bloom in the fall. Supplement with a water-soluble fertilizer to encourage strong branching and bud formation.

Mistake 5: Forgetting to Divide Your Plants

Like many other perennials, hardy mums need to be divided every couple of years or so to keep them healthy and vigorous. In spring, dig up your established plant after new growth has emerged. Use the side of a spade to slice through the plant's root ball into several pieces. Replant your new divisions and water them well. This helps give the plant's roots plenty of space to grow, and can also make it easier for them to get enough water and nutrients.

Comments (1)

Anonymous
September 20, 2020
So helpful. I'm a novice and have learned so much from my little experimental garden and this publication! Thanks.