How Long Do Mums Last When They Are in Bloom?

The arrival of garden mums (​Chrysanthemum​ x ​morifolium​, USDA zones 5-9) in nurseries and flanking the entrances to grocery stores means that fall is coming. But once you get those gorgeous mums home, how long will their blooms last? If you care for them well and never let them dry out, chrysanthemum flowers should last from four to eight weeks.

Mums are famously "short-day" plants. This just means that they begin to develop flower buds as the days begin to shorten, or after summer solstice. It's also known that the cooler weather arriving with autumn promotes bud and flower formation. If unseasonably cool weather occurs in the summer, however, mums may begin to develop buds prematurely.

If this early flowering is not warded off, the mums are unlikely to flower again. Pinch off these buds and then water well and fertilize. Water-stressed mums are the most likely to develop premature flower buds.

The best, and easiest, way to extend the life of your mums is to deadhead the old flowers. This encourages more growth, making the plant bushier and extending its flowering season. But ensuring long-lasting blooms from mums purchased in the fall and grown as annuals, starts when you first select your mum.

Choose plants with healthy foliage and no wilting stems or blooms, and avoid plants with insect damage. Select a variety of plants in various stages of bloom for a continuous display. For example, choose a few plants almost in full bloom, others that have very tight unopened buds and some in between.

Care for your potted mums properly, especially by watering them regularly. Try to place them in a partially shaded location, since too much heat and light reduces their bloom time. They won't need fertilizer, but consider adding a water-soluble plant food once a week to give them a boost. Then, be sure to snip off spent blooms as soon as they wilt.

If you've purchased mums in the spring and planted them yourself, be sure to space them correctly, depending on the variety. Mums that are crowded together produce fewer blooms over a shorter period of time than those with space to grow. Note that there are actually three different types of mums: those that bloom early in about late July, early fall bloomers that flower in September and late fall bloomers that peak in October. Whichever variety you have, most mums will bloom continuously for about four to eight weeks.

Pinching mums back is also important to encourage longer blooming periods. You'll want to start by pinching them back when the plant is just 6 to 8 inches tall, then do it again when the plant reaches 1 foot in height. By "pinching," experts mean to simply use your fingers and pinch off about 1 inch of growth from each shoot. This forces the plant's energy into growth. Continue to pinch the plants every few weeks over the summer, with a final pinch made around the fourth of July.