Mums and asters, other fall flowers

In the Garden

Ralph Purkhiser, Purdue University Master Gardener


     Autumn officially arrived last week and many people are busy changing out flower displays for the season.  Mums and asters are the traditional headliners, with thousands of these flowers purchased each year.  One of the most frequent questions I am asked is why the mums do not return the following year, even though they are sold as “hardy” mums.  There are actually several reasons for this, the first being that they may not be hardy to our particular zone.  Many of the mums sold by large retailers have been trucked in from large nurseries in Tennessee.  The varieties they grow may not be hardy enough for southern Indiana winters and will not come back unless planted in a protected location.

     Even if the varieties are hardy enough for Indiana, timing has a lot to do with success in getting mums to return.  The earlier you get the plants in the ground, the more time the roots have to acclimate and grow into the surrounding soil.  Many people want to use the mums to decorate porches and plant them only after the blooms fade.  The chance that the plants will survive is not very high.  You may be able to increase the chance of survival with some mulch.  You do not want to mulch now, but have some mulch available when the ground temperatures drop below the freezing point.  The mulch will provide insulation to keep the ground from heaving and making the roots come up out of the soil.

     If you really want to have mums that return perennially, you may plan for the option now.  I have had some success keeping mums alive in their pots by cutting them back after frost and then keeping the pots in an unheated garage or in another protected location for the winter.  You must check them periodically to make sure they do not dry out.  Watch for the returning foliage early in the winter, but it will not really grow much until warmer weather returns in the spring.  Plant the mums in their intended spot in late April.  About the end of May, cut the foliage back.  Do it again the first of July.  All of those cuttings may be placed in pots of soil and will likely grow into new plants, which also may be planted in the landscape.  By planting early in the year, the plants will establish good root systems that will sustain the plants through future winters.  After a couple of years, you may find that you have more mums than you want and can either throw away the cuttings or give the new plants to friends.

     Another popular fall plant is red fountain grass.  Although often placed with the perennials in garden centers, this particular ornamental grass is not hardy to our area.  Even with heavy mulch, it is not likely to make it through an Indiana winter.  Enjoy the plumes as long as you want, but you will either have to cut it back and over-winter it in a basement or garage or just buy new plants for next year.  You may also save the seeds and plant them inside in early spring to have the red grass for next year.  However, be forewarned that seedlings may not exactly give the same red color as the parent plant.

     My personal favorite fall flowers are the asters.  Since asters are native to more northern climates, they tend to be hardier than mums.  Like mums, they may be sheared back in late spring or early summer to keep them shorter and less likely to fall.  However, I must admit that I rarely get this done and I love the sprays of purple and pink flowers that tower up to eight feet high.  I love the way the asters mix with the goldenrod in my meadow.  It is a combination that really tells me that autumn has arrived.

     Whether the wild display of the meadow or a neat foundation planting of mums and sedums, the beautiful fall flowers play a role far more important than providing something to please the eye.  These late-season flowers are the source of nectar that is necessary to allow migrating monarch butterflies to load up on energy for the long trek south.  The bonus is getting to enjoy watching the fluttering of the butterflies in your garden.



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