No perennial garden flower adds more color to the fall season than chrysanthemum (or mum, for short). It is one of the very few flowers that starts its bloom season late in the year, providing for color into and beyond the first frost of fall. Over the years, plant breeders have developed this popular flower to the point it now is available in a myriad of colors, flower types, and bloom dates. September signals the start of chrysanthemum season when mature, potted plants are available for fall decoration and/or planting into the garden.
The word chrysanthemum is derived from the Greek words chrysos (gold) and anthemon (flower). It is the common name given to Dentranthema x grandiflorum. Until about a decade ago this plant was classified in the genus Chrysanthemum; hence the origin of its common name. Chrysanthemum is an example of a ‘cultigen’. The latter term is given to plants whose origin or selection is due primarily to human activity, oppose to having been developed in the wild.
Genetically, chrysanthemums are hexaploids and contain six sets of chromosome instead of the ordinary two. This makes them highly sterile and less competitive from the standpoint of establishing populations in the wild. It also helps to explain the differences that exist between different cultivars’ ability to thrive under certain environmental conditions. Formerly known as hardy chrysanthemum, this designation has been abandoned (more or less) in favor of garden chrysanthemum because of the varying ability of different cultivars to withstand cold temperatures.
The first chrysanthemums probably were cultivated in China as many as 2000 years ago. There it was used for its ornamental as well as its medicinal value. The roots of the plant were boiled by people in ancient times to produce a tea used to treat headache. Additionally, young shoots and petals were consumed in salads and the leaves of mums were brewed to produce a festive drink. The Chinese name for chrysanthemum is “Chu” and the modern Chinese city of Chu-Hsien was named in honor of the plant.
From China, chrysanthemum migrated to Japan around the 8th century A.D. where it quickly captured the fancy of the Japanese people. Their fondness of it caused them to adopt a single flowered chrysanthemum as the crest and official seal of the Emperor. Prominent Japanese families also included it on their family crests, and one of the highest orders of chivalry in Japan is the Imperial Order of the Chrysanthemum. The people of Japan observe a National Chrysanthemum Day which is called locally the Festival of Happiness. This represents quite a contrast with the attitude of many Europeans who consider chrysanthemum the “death flower” since in countries such as Austria and Belgium it is used primarily for grave decoration.
Modern chrysanthemum would hardly be recognized by ancient growers since most cultivars today are much showier than the single daisies that were first grown in the Orient. Chrysanthemum is a member of the Asteraceae (Composite) family whose members bear an indeterminate compound inflorescence known as a head which bear two types of florets: ray and disc. Ray florets typically are quite showy and would be what some mistakenly refer to as the petals of the compound flower whereas disk florets are smaller and, oft-times, inconspicuous.
Chrysanthemums are short-day (long night) plants that require long periods of darkness each day for flower induction and development. The critical photoperiod for flowering varies with cultivar. However, in nature, most cultivars of garden chrysanthemums are induced to bloom in mid- to late summer. Response time (until flowering) after photoinduction also varies with cultivar and according to temperature. Much attention by plant breeders has been focused on shortening the response time, resulting in cultivars which now bloom in early September only six weeks after photoinduction. Given many of the older cultivars require eight or nine weeks response time, we now have the prospect of having garden chrysanthemums in bloom from early September through October (or beyond).
Garden chrysanthemums are available in the spring as rooted cuttings established in small containers or during the fall as large, mature plants in or near full-bloom. Select a planting site that is well-drained and receives at least eight hours of sun. Chrysanthemums should be planted away from stray light that would prevent them from blooming in the fall. When planting smaller plants in the spring, be sure to space them far enough apart to allow for the future growth and development of the plant. For most cultivars this would be between 18 and 24 inches between plants; spacing 30 to 36 inches apart is preferred for more vigorous cultivars. Apply a granular fertilizer such as 5-10-5 (or equivalent) at the rate of two or three pounds per 100 square feet of surface area and incorporate it into the soil. A soluble starter fertilizer high in phosphorus (e.g. 15-30-15) applied immediately following transplanting also is beneficial.
Spring planted garden chrysanthemums should be pinched at regular intervals (every three to four weeks) to promote bushy, compact growth and more numerous flowers. For most cultivars, the last pinch should be made no later than mid- to late July to prevent the removal of flower buds which might have formed in response to photoperiod. As with other garden plants, garden chrysanthemums require about an inch and a half of water per week during the growing season. Mulching plants with materials such as bark, wood chips, or other organic materials will help to conserve moisture and also control weeds. Fortunately, garden chrysanthemums are relatively insect and disease free. Aphids, two-spotted mite and powdery mildew are the three main pest problems that should be monitored.
An alternative to planting garden chrysanthemums in the spring is to purchase mature plants in large containers which are readily available beginning late August to early September. This method allows the enjoyment of other flowering plants during the growing season to be replaced by mature chrysanthemums just beginning their dazzling display of color as the other plants fade. Select plants that are just starting to show color for greatest longevity in the garden and plant so the surface of the growing medium in which the plant is growing is even with the soil after planting and watering.
Most chrysanthemums produced for fall sale are grown in a soilless growing medium high in organic matter. When these plants are planted directly into heavy garden soils that have not been improved, the difference between the two root environments often prevents good establishment. The latter frequently results in winter kill. Therefore, winter protection (mulch) the first winter following planting is recommended.
In addition to improving the soil before planting a mature chrysanthemum into the garden, proper watering is critical. It is important to remember that all of the roots nourishing the mature plant immediately after transplanting are contained in the potting medium in which the plant had been growing, which tends to dry faster than normal garden soil. Plants should be watered regularly so as to wet the root ball contained by the pot until roots have had time to establish themselves in the neighboring soil.
There are scores of different cultivars of garden chrysanthemums from which to choose today. Each year, new cultivars with improved growth habit, flower color and garden performance are added to the list. A relative newcomer to the scene has been the Belgium or European garden chrysanthemums. These cultivars are known for plants with spectacular size and display of color. Although individual flowers are smaller than normal, they are borne in great abundance making for quite a show in the garden.
Readers should be warned that growing garden chrysanthemums can be somewhat addictive. They are easy to grow, available in a wide array of flower types and colors and extend garden color well into the fall. For those who want to discuss their addiction with others, The National Chrysanthemum Society has 35 chapters across the nation. For more information visit the Society’s web site at: www.mums.org.
REVISED: August 29, 2013