Do mums bloom all fall?

Several years ago I was in the garden center of one of Des Moines’ finest box stores in late August. Shelf upon shelf of 4″ potted mums in full bloom were waiting to be unloaded (or maybe not) and folks were filling their carts with flats of these four inch wonders. A young woman flagged down one of the associates and asked, “Will these get bigger and bloom all fall?” “Sure will, they’re a fall flower and we sell a ton of them!”

I felt sorry for the woman but decided it best to mind my own business and allow her a fairly inexpensive learning experience.

Just for the record: there is no garden mum that will bloom from late August through October. I don’t care what the dude at the box store says!

Here is what we have learned from 27 years of commercially growing garden mums.

  1. All mums will bloom for approximately 4 – 6 weeks from 10% color crack.
  2. Early mums are triggered to start to bloom in late August to early September. That means most blooms will be “browning” by late September to early October. Late season mums are triggered to start blooming in late September to early October and will be singing their swan song in early to mid November.
  3. Mums require at least six hours of full sun to fully bloom out and to keep the blooms from fading and shrinking in size.
  4. Mums require quite a bit of water, but no fertilizer, while they are blooming. Once in full bloom their water requirements diminish since the plants are no longer actively growing.
  5. Mums require good drainage. Sitting in a saucer of standing water encourages root rot and disease. A slow, gentle watering that completely saturates the root zone is the goal. Water until there is a steady flow exiting the drain holes in the bottom of the pot.
  6. Water the mum when it needs it – not when it’s convenient. Overwatering will lead to root rot. Always check the soil in the pot by inserting your finger into the soil to the first knuckle. If it’s starting to feel dry and crumbly it’s time to water. If it’s cool, moist and sticks to your finger it has plenty of moisture.
  7. Warm, windy days will dry out the mum much faster than cool, overcast days. Always water according to weather conditions.
  8. There really is no way to speed up/slow down or control the bloom time of a garden mum. They are full sun plants and will perform best in full sun with ample amounts of water. Setting “green” or non blooming plants in the shade, under the deck or in the garage for more than a couple of days causes the mum to shut down causing the buds to abort. (This is also why mums that have been marketed in “warehouses” or shaded areas in garden centers don’t always bloom satisfactorily.)
  9. All mums marketed in the fall are now called “garden mums.” They are not intended to overwinter from a fall planting, although some people have good luck if planting early in the season in a sunny, sheltered area protected from winter wind. Grower have been encouraged to discontinue using the term “hardy mums,” primarily due to the fact that the new hybrid mums have been bred to bloom longer, have bigger blooms, a more mounded habit and better color retention (less fading). With these improvements some of the vigor of the old fashioned species mums has been lost. Most importantly, our freezing/thawing cycles have become more erratic causing mums to heave out of the soil desiccating the roots. Tender, new growth in spring is easily injured due to late spring frosts that have become more common in our midwestern climate.

So, if by late August your summer flowers have sailed into the sunset, but a flower fix is still needed, early season mums are the remedy. If summer flowers still look great in September, late season mums will deliver for the cooler, darker days of late fall.

Our mum season here at Groth’s starts August 21 with the early season mums. We grow all colors in all three seasons: yellow, orange, red, white, pink and lavender. Midseason mums are usually ready by early to mid September and late season mums should be ready by late September. They will remain in the field until the buds are big enough to go home and bloom their hearts out!

May all your days be filled with flowers,


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