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Mums and Fall Plantings

Jim Boxberger
Posted 9/12/25

With the colder nights and scattered frost about, many of the summer annuals and vegetables in the garden have gone to mush, but that doesn’t mean the planting season is over. Fall mums, …

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Garden Guru

Mums and Fall Plantings

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With the colder nights and scattered frost about, many of the summer annuals and vegetables in the garden have gone to mush, but that doesn’t mean the planting season is over. Fall mums, asters, Montauk daisies and flowering cabbage are blooming now through the fall. Now even though many of the mums and asters are perennial and will come back next year, they won’t grow well the next year unless you know how to prune them. I’m not talking about trimming them back before the winter, as with other perennials, the tops will completely die off over the winter anyway. The pruning needs to be done in the spring when they start to grow. You see, mums and asters if not pruned, will grow to about three feet tall but only have two or three stems and won’t flower very much. Both of these plants need multiple pruning as they grow so that they will thicken up and branch out. When they grow to about five inches tall, cut them back to three inches. Then when they grow to seven inches, cut back to five inches. By the time you do the second pruning they should be fairly well branched, if not do a third pruning at about eight inches back to six. With all that pruning, that is why most people just buy new mums every Fall.

 Fall is a great time to plant trees, shrubs and perennials too, for several reasons. The first being that they will not go into transplant shock as they are already going dormant for the winter. Dropping needles or leaves, or dying back completely like perennials, when this happens the plant is sending all its energy down to the roots to be stored for the winter. So when you plant now, the roots get a chance to grow without having to support the top of the plant. By the time spring rolls around your root base will have increased and now it will have a much easier time supporting plenty of top growth. The second big reason because the plants are going dormant, you won’t need to water them, and one application of fertilizer four to six weeks after you plant will be all you’ll need until next May or June. By planting before Thanksgiving your plants root base can almost double by the time spring finally rolls around in March and April, so your roots will be able  to supply your plants with much more water and nutrients to provide superior growth. For any trees or shrubs that bear fruit or flower, the old saying goes, the more root - the more fruit. Adding a little mycorrhiza in the spring will help this even more, but don’t add mycorrhiza now as it will probably die off over the winter, that is why it is best to add it in the spring when the frost is out of ground.  

 So with all these reasons why planting in fall is the best time of year, why don’t more people do it you might ask? The simple reason is – nobody gets spring fever in September and October. That’s it, nothing fancy, it is all psychology. It is a psychological phenomenon when the daylight hours start getting longer and the temperatures start to rise in the spring we get more energy and want to get our hands in the dirt and plant. In the Fall when daylight is dwindling and the temperatures are colder we go into hibernation mode and want to sit on the couch and watch football. That is why most garden centers like us, have to put their plants on sale to move product out before it is time to pack them away for the winter. Besides the mums, asters, cabbage and kale for Fall decorating, we have straw bales and pumpkins, and corn stalks should be in soon.

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