JOPLIN, Mo. — There aren’t many things that announce the fall season like a mum in full bloom. Much like the turning of the leaves on trees, fall mums — also known as chrysanthemums — are starting to show their colors.
But as the month of October fades into November, and outdoor tempatures begin to drop, how can you keep these flowering fall plants from becoming casualities of the outdoor elements?
How Often Should You Water?
One of the quickest ways to shorten a mums blooming period is with improper watering. Autumn’s temperatures may be cooler — but the drier, less humid air also takes moisture away much faster. That means plants can dry out quickly, which will greatly shorten blooming times.
“The thing with mums is that they dry out very, very quickly. So I would recommend checking them daily. If it’s a really hot, dry day, you may even have to water them twice a day. That is probably the number one issue that people have with mums, is that they just dry out really quickly and they don’t even notice it until it’s too late. Once the plant has completely dried out, it’s really hard to rehydrate it and get it looking good again,” said MU Extension horticulture educator and field specialist, Kelly McGowan.
McGowan says you should check the soil of your plants daily with the tip of your finger or with a moisture meter. If the soil is dry down at the root level, it’s time to water. Make sure to always water enough that the roots deep down in the container receive water. If the roots get too dry, they shrivel and stop taking in nutrients.
How Much Sun Is Too Much?
As much as mums need full sun to develop full blooms, that same hot sun can also end the growth. In fact, too much sunlight can shave weeks off of the amount of time they will flower.
By simply keeping your mums in a partially shaded location or out of the full strength of mid-day sunlight and heat, you can add as much as two weeks to how long they will flower.
“We’re treating these more as a potted plant, so they don’t need eight hours of sunlight a day or anything like that when they’re in a pot. Just make sure they’re getting some sunlight but not baking on a really hot day out in the direct sun,” said McGowan.
Is Fertilizer Necessary?
If you’ve purchased potted mums to display during the fall, McGowan says fertiziling them may not be necessary.
“Most of the potted mums are probably going to have some type of slow release fertilizer in the soil already, and will probably have all it needs between now and when the plant finally stops blooming,” says McGowan.
On the other hand, if you intend to plant fall mums, wait to begin their fertilization until the spring. Fall fertilization can actually reduce the hardiness of mums to survive cold winters.
How Much Cold Can Mums Tolerate?
According to the USDA, the lowest minimum temperature that planted mums can generally survive is right around 20 degrees Fahrenheit because the roots themselves are insulated by the earth. Potted mums, however, won’t tolerate cold temperatures very well.
“Mums can tolerate a little bit of light frost. But if we’re getting anything more than just a light frost, like if a freeze is projected, I would go ahead and bring those inside just to be on the safe side,” says McGowan.
The University of Missouri Extension offers a suggestion: When purchasing your mums, look for the hardy variety. Often refered to as “garden mums,” hardy mums have full foliage and larger blooms. If planted at the right time, these mums can come back each season to bloom again.