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Time to talk mums

As a Master Gardener, I’ve been contacted by people who were disappointed that the beautiful pots of chrysanthemums they purchased last year did not survive. I’d like to help remedy that situation.

Chrysanthemums, commonly called mums, can provide swaths of color in late summer and fall. Mums are among the last flowers to bloom as our Pennsylvania growing season comes to an end. Their displays often coincide with changing fall foliage to give us a last dose of brilliant colors before the gray shades of winter take over.

Knowing a little about mums and putting that knowledge to work will go a long way to helping them survive and thrive. Given the right conditions, garden mums can return year after year. They are surprisingly easy to grow and come in a variety of colors and types.

All mums are not created equal, so let’s begin by differentiating between garden or hardy mums, which are perennials suitable for growing in Pennsylvania landscapes, and florist mums, which are frequently grown in greenhouses for the cut flower trade or sold as houseplants. Some florist mums might be adaptable to southern climates but are usually unsuitable for locations with cold winters and shorter growing seasons.

As a general rule, garden mums prefer well-drained locations with plenty of sunshine. Good drainage is essential. Mums planted in consistently wet areas will struggle to survive and are especially susceptible to winter injury. While some varieties may tolerate part shade, most will perform better in full sun. Mums that do not receive enough sunshine may appear straggly and produce smaller blooms than those grown in sufficient sunshine, or might not survive at all.

Although mums are tolerant of a variety of soil types, adding organic matter such as compost, well-rotted manure, or leaf mold can improve soil structure and help mums get off to a good start. The organic matter should be worked into the soil to a depth of approximately 12 inches before planting. Mums are heavy feeders, so it’s important to give them the nutrition they need. Depending upon the nutrient levels in the soil, it may be necessary to add fertilizer prior to planting. Be sure to follow label directions, being careful not to add too much or too little fertilizer for best results. Soil test kits, which will provide a soil analysis and recommendations, are available at the Penn State Extension Office.

Mums should be planted far enough from each other to allow room for growth which, given the right conditions, may be considerable. The appropriate distance is determined by the anticipated size of the mature plant. Most plants come with tags indicating the variety name and its size at maturity. Use that information as a guide. In some cases, 18 inches between plants may be enough, but for larger varieties, as much as 30 to 36 inches between plants may be needed. Spacing between plants isn’t just a matter of aesthetics. It ensures that each plant receives adequate sunshine and isn’t competing with its neighbor for moisture and root space. It also allows for good air circulation between plants which can help them avoid powdery mildew.

Pinching, which is the process of pruning off the growing tips of stems to encourage branching, is done to create shorter, bushier plants with sturdier stems that can keep flowers upright and stand up to wind and rain. Mums that are not pinched can grow tall, lanky stems that often fall over when in bloom. Pinching can be done with fingers or with hand pruners. Usually about ¢ inch to 1 inch is removed and the cut is made at the point where a leaf is growing out of the stem, leaving the leaf in place. Generally speaking, pinching can begin once the plant reaches about 6 inches in height, followed by additional pinchings, if needed, depending upon growth rate. Generally speaking, in our area, pinching should be discontinued by early July, because some mums begin to set flower buds at that time. Some newer varieties of mums have been introduced which do not need pinching, so be sure to check labels when purchasing mums.

In Central Pennsylvania, many people think of mums as fall flowers and purchase them in September and October. A word of caution is needed here. If you expect your mums to survive the winter, you need to plant them early enough to allow sufficient time for their roots to become established before freezing temperatures set in. Many a newly planted mum has been lost due to frost heave, which can damage the plant’s roots or cause it to be pushed out of the ground as a result of freezing and thawing cycles. Mums, much like other perennials, can be planted in spring, giving them an entire growing season to become established in their new homes before winter sets in. If mums are planted in summer, extra care must be taken to ensure that they have adequate moisture to deal with the stress of summer sun and heat. Mums can be planted in the fall, but the earlier the better.

Some of our local greenhouses and garden centers offer big beautiful pots of mums in full bloom in early fall, and many gardeners can’t resist bringing home these beauties. Keep in mind that the larger and more developed the plant, the more care should be taken to reduce transplant shock, which occurs when roots are disturbed and their ability to take up water is impaired. Water the plant thoroughly about an hour before removing it from the pot. This will keep the root ball moist during the transplanting process. Water well as soon as the plant has been placed in the ground and be sure that the plant receives adequate water for the next week or so while its roots are becoming established. The soil should be moist, but not soggy. Remember, mums do not like wet feet. To lessen the risk of frost heave, mulch can be used to stabilize the ground temperature and should be applied after the ground has frozen.

Mums are generally classified by the shape and configuration of their flower petals, and the National Chrysanthemum Society lists 13 classes of bloom at http://www.mums.org/chrysanthemum-classes/

Garden mums are available in shades of yellow, orange, bronze, copper, lavender, pink, red, and white. To really bring out those colors and help pollinating insects at the same time, I’ve planted native asters in shades of purple, violet, and blue alongside chrysanthemums to make a vivid display of color to enjoy at the end of the season.

If you have questions about chrysanthemums, please call the Clinton County Master Gardener Hotline at 570-726-0022, ext. 3826. The Master Gardeners will be happy to help.

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Debra Burrows, PhD, is a retired Penn State Extension educator. She can be reached at dcb3@psu.edu.

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