Everywhere I go I see huge displays of fall garden mums for sale. Beautiful colors and a reminder of cooler days to come. Mums are a great addition to containers and the landscape to add color when our summer flowers are faded or finished. With a little extra planning those mums you buy now can be a permanent fixture in your garden.
Garden mums are hardy in zones 5-9 and the one interesting thing about them is that flower initiation is induced by longer nights. Keep that in mind when choosing a location to plant your mums. Avoid street lights or other night lighting situations because the mums would not get the length of darkness required to initiation flower bud formation. The location should provide 6 to 8 hours of sunlight and be well-drained soil. Mums don't like wet feet so avoid low lying areas or heavy soils. Consider improving the planting location by incorporating compost into the soil.
You'll want to plant them in the ground as soon as possible to give them time to root in before the winter. Mums are shallow rooted plants so providing supplemental irrigation if it's dry is needed as is making sure to mulch them with an organic mulch. They are notorious for heaving which is shifting up out of the ground as the ground freezes and thaws and adding a 4-6 inch layer of straw after the ground freezes will help provide needed protection. After they have gone dormant in the fall, don't cut them back. Leave up the growth to help provide an additional layer of protection to help them through the winter.
So let's fast forward to next spring. What do you do now? Fertilize them once a month once growth resumes in the spring with July being the final month of fertilizing. To encourage bushier mums with more flowers you can pinch them back (removing 1-2 inches of growth) this also prevents super leggy mums with few flowers that flop over. The first pinch should be down when the mums are 8-10 inches high, second pinch is around summer solstice (longest day of the year) or by July 4th. If you want even bushier mums you can add another round of pinching in between the other 2. Make sure to provide moisture during the growing season if it's dry.
If your fall planted mums are unsuccessful surviving the winter but you are wanting to still have them in the landscape, consider purchasing mums in the spring. Spring planted mums have a longer time period to establish themselves in the soil improving their winter survivability following the recommendations for winter protection I mentioned above.