The hardy garden mum is a hybrid called chrysanthemum x morifolium. Its ancestry goes back hundreds of years. Chrysanthemums were grown in China as early as 550 B.C. All the cultivars are considered hardy in zone six although some are best treated as an annual.
Garden mums are available in almost all colors except blue. The flowers range in size from one-inch cushion mums to six-inch "football" mums. They are excellent potted plants and cut flowers. Chrysanthemums are propagated from seeds, cuttings and divisions.
Blooming plants from florists are fine gifts but they have no place in the garden. Though they may be the same cultivars that could do well in the garden they have been grown under glass, coddled and forced to bloom out of season by manipulating their day length. Give them as gifts or enjoy them as container plants, but don't expect them to survive the winter in the garden.
Rooted cuttings purchased in small pots early in the season are inexpensive and develop into robust plants by fall. The number of cultivars sold as rooted cutting in the spring is greater than the choice available in late summer. This is particularly true if you purchase plants from specialty growers. You have the opportunity to pinch back the plants so they develop more blooms. You can thin the stems of large-flowered cultivars, remove laterals and disbud to produce huge blooms.
Most potted blooming mums are cushion mums. They do well without pinching or disbudding and can be transplanted in full bloom without a setback. .They cost a little more than rooted cuttings purchased in the spring, but someone has done a lot of work for you.
Most mums make it through the winter in zone six. Failure to survive is usually the result of heaving. Chrysanthemums are shallow rooted and alternate freezing and thawing can lift them out of the ground. The roots dry out and the plants die. A heavy mulch of straw eliminates the problem.
There is a difference of opinion about when chrysanthemums should be divided. At one end of the spectrum are those that advise dividing each year. Many divide every two years and three or four years is the far end of the spectrum. The centers of undivided mums die out and the blooms diminish in size and quantity.
There are two options open to gardeners dividing the mums. The quickest and the easiest is to dig up the clump, discard a weak center and divide the remaining clump into three or four smaller clumps A larger number of new plants can be obtained by stem cuttings.
When the new shoots are about two inches high pull them from the clump. Remove the lower leaves from the cutting. Plant the cutting in a two-inch pot filled with soilless potting mix. Rooting compounds speeds the development of roots. Mums rooted easily and it is possible to successfully root cuttings without using rooting compounds. Put the pots in plastic bags or it in a cold frame. Do not allow them to dry out in. Roots develop in between two and three weeks.
Some gardeners like to
move the rooted cuttings into larger pots for additional growth
before setting them into the garden. The young plants can also
be held in a nursery bed during the summer and set into the garden
in late summer. Cushion mums may be flowered in six-inch pots
and then discarded after blooming.
Unlike cushion mums, the tall mums must be cut back to cause them to branch and produce a large quantity of blooms. Pinch the plants back when they are between six and eight inches tall. Pinch the new growth back when it is between six and eight inches tall. Do not pinch back after mid-July.
The large flowered mums, and some of these can have blooms as large as eight inches in diameter, require special attention to develop their potential. Each plant must be reduced to three or four stems early in the season. All laterals or side stems must be removed from the main stems. When the plant begins to develop buds they must all be removed except for a single central bud on each stem. Fertilize them every two weeks with a half strength liquid fertilizer. Keep them well water.
The National Chrysanthemum Society divides mums into thirteen classes. The Society has a web site that defines and illustrates the plants in each class. Check their web site at www.mums.org/. Those of you living near Longwood Gardens at Kennett Square, PA should visit the chrysanthemum display in the Conservatory. The cascading mums are awesome. You may obtain information about their Chrysanthemum Festival from their web site at www. longwoodgardens.org.
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Copyright © 1999-2009 Frank H. Sommer
Sommer in the garden
zone 6 gardening Pennsylvania
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Web site created September 26, 1999
Updated November 11, 2009