Fall Chrysanthemum Care

When I think “fall”, I can’t help but imagine chrysanthemums and ornamental grasses. In my opinion, fall is all about rich colours and comforting textures, and chrysanthemums (or, as they’re better known, “mums”) have both in spades. They also look phenomenal in container arrangements with my beloved ornamental grasses, but I digress.

Mums may be some of the most popular fall-blooming flowers. In Guelph, it’s common to drive through residential neighborhoods and pass by a rainbow of mums in big, cheerful porch pots. As with most wildly popular flowers, breeders have gone wild with creating new varieties to suit every preference under the sun. You can find early- and late-season flowering varieties, flowerheads in single, double, and petal-packed cushion-shaped blooms in virtually any hue. 

When we talk about caring for mums, we’re generally talking about two different categories: potted—or “florist”—mums, and garden mums. Here’s how to keep them both looking radiant for the rest of the season.

Caring for Potted Mums

Taking care of mums in pots is pretty simple. We tend to see a lot of folks visiting us at our garden centre to pick out mums that are already peeking out of their pots in neat round mounds. You can display them in the pot they come in, or you can repot them into a larger container as part of an autumnal arrangement.

When repotting chrysanthemums, make sure the plant has been watered fairly recently and the soil is still damp. Repotting is generally much more successful when soil is left clinging to the roots. Turn the old pot upside-down slowly and gently coax out the root ball. You may need to knock gently on the bottom of the pot to loosen and free the plant. Once removed from the pot, transfer to a new pot with enough room that the top of the root ball will sit about an inch from the rim of the pot. Fill in the spaces and top off with high-quality potting soil with excellent drainage. Allow the repotted plant to sit in indirect sunlight and wait until the soil has dried on top before watering.

Once your mum has dried out, water it deeply. Chrysanthemums are “water pigs”, not unlike hydrangeas, and if you let them dry out, you’ll cut the blooming period short. Feed them with a balanced 10-10-10 liquid fertilizer monthly, or add slow-release water-soluble fertilizer granules into the potting soil before repotting.

You can also keep potted chrysanthemums inside for an indoor display, though you’re not likely to get more than 3 or 4 weeks of flowering from them this way. Chrysanthemum care indoors is a little more finicky, as the plants aren’t able to get the same airflow and temperature fluctuations they enjoy outside. If you do keep them indoors, keep them in a spot that receives bright light during the day but no light after dark (including street lights or porch lights). The area should also have good airflow and low humidity to keep fungus at bay. Water chrysanthemums daily, aiming the stream directly at the soil to avoid getting leaves or blooms wet.

If you have pets, indoor mums may not be a good call. Some of the compounds in the plant can be toxic to dogs and cats.

Garden Mum Care

One of my favourite things about garden mums is how easy it is to keep them happy. In the Guelph area, chrysanthemums tend to do pretty darn well with nothing more than a little fertilizer and water. Pyrethrum, a common pesticide, is actually derived from chrysanthemums—so you can imagine how rare it is for them to develop an insect problem. Chrysanthemums are also pretty resistant to deer and rabbits thanks to their texture.

Caring for mums outside mainly involves keeping their soil evenly moist. Monitor the soil at least once daily to make sure the soil doesn’t dry out, which will bring the flowering period to an end. Water them the same way you might water roses, keeping the stream of water as close to the soil as possible. Mixing 10-10-10 slow-release fertilizer into the potting soil will make sure they have the nutrients they need. 

While chrysanthemums are generally considered annuals, some varieties can last 2-5 years if you do a really great job of overwintering them. To prepare your mums to last through the winter, find them a very well-sheltered spot and apply a thick layer of mulch before the hard frost. If the plants die anyway, don’t take it too hard—even the best intentions can’t guarantee a 100% survival rate.

Mums Not Blooming?

The most common mum-related question we hear at Royal City Nursery is “why aren’t my mums blooming?”, and there are two likely reasons.

The first is that the watering schedule has been inconsistent. As I mentioned, evenly, consistently moist soil is the key to keeping these fall beauties blooming longer. If the soil dries out, the bloom supply will dry up.

Another possibility is the weather has been too warm. Being late-season bloomers, chrysanthemums bloom best when the nights are cool. If we get a week or so of unseasonably warm evenings, the plants won’t bloom as well. The way I see it, the warm evenings are definitely a nice consolation prize!

We see a lot of mums passing through our garden centre around this time of year, so we’re pretty well-versed in troubleshooting them. If you’re noticing anything odd while taking care of your mums, or you simply have to expand your collection, visit us at our plant nursery in Guelph! We’d be happy to answer your questions, or introduce you to some gorgeous mum varieties in your favourite fall colours.