Don’t kick potted mums to the curb: They’re perennials you can keep
Signs of autumn are most apparent in colder climates, where fall foliage sets the landscape ablaze. But regardless of your location, chances are there’s one familiar seasonal sight each year: potted chrysanthemums perched on porches, hanging in baskets, temporarily planted into borders.
And soon, they get kicked to the curb with decaying jack-o’-lanterns.
Curious and frankly disturbed about the ritual carnage, I asked a few of my Long Island, New York, neighbors why they discard their mums. The universal response? They believed them to be annuals.
Garden chrysanthemums are actually perennials, hardy in horticultural zones 5-9. That means they can survive winter in roughly half of U.S. states. It’s true, the plants can’t withstand the deep freezes experienced in parts of New England and the northern and central portions of the Northwest and West. Nor can they handle the blazing summer heat in the southern half of Florida, south Texas, and part of Southern California into western Arizona.
But that leaves roughly half the country primed for growing mums in their gardens.
There are, indeed, annual chrysanthemums, but they are primarily used in the florist trade or sold as potted gift plants, typically in stores like supermarkets, as opposed to nurseries. Still, check the plant tag to know what you’re getting. The garden-variety perennials will be labeled chrysanthemum morifolium; annuals belong to the Chrysanthemum multicaule species.
No plant tag? Check the foliage: Perennial mums have broad, deeply toothed leaves; annuals have narrow and less-notched foliage.
Native to China, perennial chrysanthemums are available in shades of orange, red, rust, pink, purple, yellow, cream and white. Most grow to 1 to 3 feet tall and wide, reaching their mature sizes in about three years. In frost-free zones, they provide a second bloom in spring.
Consider using the plants alongside sedums, asters and goldenrods for a colorful seasonal display in the center of your garden bed.
Plant mums in well-draining soil as early in the season as possible. Spring would be ideal if you could find them at the garden center, but that’s not the case in many parts of the country. Although I’ve succeeded with fall plantings, you might not if temperatures dip below freezing within six to eight weeks of planting. If you’re not willing to gamble, enjoy the show until your plants go dormant, then stash the pots in an unheated garage or cellar over winter. Water them occasionally — very lightly — then plant them in spring after the danger of frost has passed.
Regardless of timing, incorporate compost into the soil to improve drainage, and set the plant into the ground at the same depth as it was growing in its container.
Allow sufficient space between plants to prevent crowding, which can lead to mold, mildew and fungal diseases. If plants become overgrown, divide them in spring, just after new growth appears. It’s a great way to make free plants.
Mums thrive best in full sun with consistently moist soil and will benefit from regular fertilizer applications, as they are heavy feeders.
Spread 2-3 inches of mulch around the plants to help retain soil moisture and suppress weeds. Add another inch or two after the ground has frozen to protect roots from the freeze-thaw cycles of winter.
Allow dormant plants to stand in the garden over the winter; the above-ground plant matter, although dry, will help to further insulate roots. Cut them back in spring after new growth emerges.
Starting in their third year, prune back one-third of the plants’ growth three times per season: at the beginning and middle of June and again during — but no later than — the first week of July. Don’t worry about removing flower buds; the practice will stimulate the production of more blooms and create fuller, bushier plants.
If chrysanthemums aren’t hardy in your zone, you can still partake in the festivities. Potted mums don’t do well in the heat, so avoid temptation when you see them for sale in late summer. They’ll survive better — and longer — if you wait until temperatures cool.
When overnight frost is predicted north of zone 5, move pots into a well-lit, cool location indoors. Water deeply when the soil dries out, but don’t let it remain dry for too long. The plants won’t necessarily thrive, but they should remain alive until spring, when you can bring them back outdoors.
In the deep South, follow the same procedure when spring or summer temperatures rise into the 80s, and care for plants indoors until things cool down in autumn.