Charles T. Behnke
The garden chrysanthemum is one of the most exciting flowers that can be grown in the home landscape for late summer and fall display. Garden mums require a minimum amount of care and do well even under some adverse conditions. There are cultivars (varieties) with color that range from white to yellow, pink, bronze, red and their hues. With hundreds of cultivars available, the choice of plants to grow is unlimited. To have a more interesting collection of mums, however, plant cultivars of various types such as singles, anemones, decoratives, pompons, spoons, spiders and standards.
The term garden mum applies to chrysanthemum cultivars that will flower naturally in Ohio and be early enough to avoid a heavy frost. The term "hardy" has been abandoned by most suppliers since hardiness of garden mum cultivars may vary significantly from one season or area depending on weather and previous cultural conditions.
Garden chrysanthemums are planted in the spring from established cuttings. This is contrary to years ago when they were offered primarily in the fall as clumps. Today the plants are being sold along with annual flowers and vegetables. Most of the plants are sold in pots that must be removed before planting. The plants generally have had at least one pinch, which results in a well-branched plant.
The site for planting should be well drained and receive plenty of sunlight. The plants should be spaced 18 to 24 inches apart, and some of the more vigorous cultivars may need 30 to 36 inches. Enough space should be allowed so the plants can develop to their maximum. Plant to the same depth they were growing in their containers and no deeper. The plants should be thoroughly watered after planting.
Fertilizing the plants will develop good, green foliage with optimum flowering. Apply a complete dry fertilizer such as 5-10-5, 5-10-10, 5-20-20 or equivalent at the rate of two to three pounds per 100 square feet of bed area. The dry fertilizer should be watered in after it is applied. Soluble fertilizers such as 15-30-15, 20-20-20 are also quite satisfactory to use if desired. Follow the rate of application on the package or container. Fertilization can be discontinued after flower buds form in late July. As the plants grow, they should be pinched to produce compact plants with more flowers. If this isn't done, the plants will become tall and leggy. Also, if the plants become quite tall, light will be excluded from the lower part of the plants, resulting in unsightly dead leaves.
New shoots should have the tops removed by pinching them off between the thumb and forefinger. This practice should be followed, leaving two or three leaves on the shoot, whenever it becomes three to four inches long. This practice can be timed so that the fertilizing and pinching can be done the same day. This will usually be once a month from May-July. However, with most garden cultivars, the last pinch should be made no later than August 1. If pinching is continued after this date, flower buds will be eliminated from the plants. It may be suggested with some cultivars that the last pinch should not be made later than July 15. If it is, follow the directions given.
Weeds, as with many other plants, may present a problem with growing garden chrysanthemums. These can be removed by hand, or an organic mulch could be used at the time of planting. Materials such as shredded bark, wood chips, coarse peat moss, peanut hulls, sawdust, or straw will do a good job of keeping the weeds down and conserving moisture in the soil if applied about two inches deep. Organic matter that breaks down rapidly such as straw, will require an extra application of fertilizer to compensate for the nitrogen loss. Apply this fertilizer in addition to that which is applied for the plants. However, you will only need to apply it a couple of times and then stop. Pre-emergent herbicides which are labeled for such use can also be effective if applied in early spring before weed seeds germinate. Landscape fabrics and decorative gravel are also effective in weed control.
An important cultural practice with garden chrysanthemums is applying adequate amounts of water. During some summers, rainfall may be plentiful enough to eliminate most additional watering. However, the plants should be watered when the soil starts to dry. Apply enough water to soak the soil to a depth of four to six inches. This is best done by using sprinklers rather than hand watering. It is best to apply the water during the day so the foliage will dry off before nightfall. Otherwise, leaf and flower diseases can become a problem.
Fortunately for garden chrysanthemum growers, most insect and disease problems are controllable. The common insect pests are aphids, two spotted mites, and powdery mildew which can usually be controlled by spraying or dusting with labeled products. One disease that cannot be controlled with chemicals is verticillium wilt. Avoid planting in verticillium contaminated areas for several years.
The garden chrysanthemum, in most instances, should be considered an annual flower by homeowners. Therefore, when frost kills the tops of the plants, cut off the dead stems and remove from the garden. Sometimes, mums will come up the next spring if just the tops of the plants are cut off. If you prefer to try to keep them over winter, cut off the dead tops and cover the plants with mulch to a depth of three to four inches.
For gardeners looking for specific cultivars, the following are widely available in the trade and should do well in Ohio.
This publication contains pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide. It is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used. Due to constantly changing labels and product registration, some of the recommendations given in this writing may no longer be legal by the time you read them. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author, The Ohio State University and the Ohio State University Extension assume no liability resulting from the use of these recommendations.
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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
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