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Sunday, September 24, 2023
Growing Together: Growing hardy mums that’ll survive the winter
Chrysanthemums can be toxic to dogs and cats if they ingest large amounts, says gardening expert Joanne Young. JOANNE YOUNG Joanne Young

As we start thinking of fall, the one flower that probably comes to mind first is the chrysanthemum, also known as mums.

There are basically two categories of mums: greenhouse and hardy varieties.

The greenhouse varieties are mums that have been forced in a greenhouse environment and are commonly sold in grocery and big box stores throughout the year, especially at special times of the year such as Easter and Mother’s Day.

These greenhouse varieties are not necessarily outdoor hardy. The other category of hardy mums is commonly sold at garden centres in September and October only.

Hardy mums usually grown outside, receiving the same light and conditions that they would receive if they were growing in your garden.

Unlike the greenhouse varieties, the hardy mums have the ability of overwintering in our gardens. I will address the reasons why some don’t survive over winter further down.

All chrysanthemums come into bloom late summer/fall due to a physiological reaction called photoperiodism. Plant photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light and dark periods.

They are classified under three groups according to the photoperiods: short-day plants, long-day plants, and day-neutral plants.

Long-day plants will start to set flower buds and come into bloom as the days start growing longer, so they typically bloom early spring to early summer.

Short-day plants will start setting flower buds as they amount of daylight shorten and the amount of darkness lengthens. They come into late summer to fall.

Day-neutral plants do not initiate flowering based on photoperiodism. Instead, they may initiate flowering after attaining a certain overall developmental stage or age.

To get mums to bloom at other times of the year (greenhouse varieties) the lighting provided in the greenhouse will be set to simulate the lighting outdoors in late summer.

Most mums will bloom anywhere from four to eight weeks depending on the temperatures. If the temperatures are cooler when they are in bloom, the flowers will last longer.

Mums come in all sorts of colours, including white, yellow, orange, rust, pink, purple and burgundy.

Although we often just see button mums available for sale, they also come in many flower types: anemone, cushion, quill, pompom, spoon, spider and thistle.  

The hardy fall mums are perennial plants in good growing conditions. I know many of you will say, though, that you have tried planting your pots of mums that you bought and decorated your porch with and have had no luck overwintering them in the ground.

Here are a few tips to help them survive the winter:

  1.  Choose a variety that is cold-hardy to your winter temperatures (Zone 6 or lower in Niagara region).
  2. Spring-planted mums are more likely to survive the winter in the ground than fall-planted mums. Unfortunately, mums are rarely sold at garden centres in the spring. You may have more luck finding them available on-line at that time of year.
  3. If planting your pot of mums in the fall, try and get them into the ground as early as possible. If you wait too long the roots do not have a chance to get established before the ground gets too cold. The frost is more likely to heave the root ball out of the soil. Once planted, mulching over the root ball will help insulate the roots. 

Here are a few more tips when growing mums in your garden:

  1. Please note that mums can be toxic to cats and dogs if they ingest large amounts. Cats are more sensitive to mums and show allergic dermatitis if they touch them. So, you’ll want to ensure you keep your potted and planted mums away from any curious furry friends.
  2. To keep plants looking leggy, trim back the stems of the plant to a couple of inches high by mid-June. This will help the plant to branch out and keep from getting too tall. The more branching there is the more flowers it will bear.
  3. Divide the clumps of mums every two to three years to keep it healthy and productive. Best to divide in the spring.
  4. Mums prefer a well-draining soil, that has access to consistent moisture. They do not like to dry out for any length in time.
  5. When buying mums this fall, whether to have as a decorative pot at your entrance or to plant in your garden, choose ones that the flowers are just starting to open up so that you can still enjoy the blooms for weeks to come.

Joanne Young is a Niagara-on-the-Lake garden expert and coach. See her website at joanneyoung.ca.

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