Hartley Magazine

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Growing and Propagating Chrysanthemums

Chrysanthemums can come in a variety of colors. Some flower earlier than others. For the home grower mums might come into flower quite late in the season.

Stores full of beautifully mounded chrysanthemums is a sign that fall is arriving. If you buy some of these mums for a colorful fall display, you shouldn’t just toss them out when the flowers fade. Greenhouse owners can easily keep these plants going and also propagate more of them. Here’s how.

First, you should know that there are both hardy and non-hardy mums. The non-hardy varieties must be overwintered in your greenhouse. Virtually all the exhibition-style chrysanthemums you read about or see at shows are not winter-hardy. Of course, any mum can be planted outdoors in spring and left in the garden all summer, even ones that must be potted and brought back indoors for winter. Hardy varieties, in contrast, can survive the winter outdoors, although there’s no guarantee that they’ll do so. For best results, you should cut these plants back to the ground after flowering and cover them with an organic mulch to help keep the roots warm. Freeze/thaw cycles, however, can still kill the plants. The best way to avoid this possibility is to pot the plants and move them indoors after you’ve cut back the stems.

Caring for chrysanthemums isn’t difficult. Mums like a nice loamy soil, with a lot of organic matter and a pH of around 6.5. They also like plenty of water (about an inch a week) and once-a-month fertilizing when they are actively growing. As the plants get larger, they should be watered two or three times a week to keep them growing. Potted plants may require a little more watering and fertilizing than plants grown in the ground do. Because nitrogen promotes leaf growth, use a fertilizer that is relatively low in nitrogen, such as a 5-10-5, to promote good flower production. The way to get a mum to bloom earlier than normal is to reduce the amount of daily light it receives to mimic later-season conditions.

Pots of colorful mums ready for display. Typically these plants are grown in commercial greenhouses using special techniques to get them to bloom early. You can force your mums to flower early, but covering them for a certain number of hours per day to mimic the shorter days of fall.

Pinching chrysanthemums is often essential to get the form you want. Many smaller varieties of mums, such as those that flower around Halloween, are pinched back about every six weeks to give the plant a rounded shape. Pinching also tends to create more, but smaller flowers. If you want a plant that’s compact but bushy, begin with a dwarf variety and let it grow in the greenhouse until it’s about 6” tall. Then pinch off about an inch of each leader, which will force the plant to grow more side shoots. After about six weeks, pinch off the leaders once again to shape the plant. It can now usually be left to grow into a nice, rounded mound.

If you want to propagate a favorite mum, there are two ways to do this. One is to take a piece from a large, rooted clump and plant it. If this is a winter-hardy mum, it can simply be replanted in the garden and given a little fertilizer and lots of water. For non-hardy mums, the plant must be put in its own pot. A second method of propagation is with a four- to six-inch-long cutting from the plant. Simply wet the bottom of the cutting, dip it in rooting hormone, plant it in potting soil, and wait for it to grow. I usually do this right after the plant’s flowers have died back, but you can do it at almost any time of year.