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Growing Potted Chrysanthemums Next Generation Science/Common Core Standards Addressed HS‐LS2‐5. Develop a model to illustrate the role of photosynthesis and cellular respiration in the cycling of carbon among the biosphere, atmosphere, hydrosphere, and geosphere. [Clarification Statement: Examples of models could include simulations and mathematical models.] [Assessment Boundary: Assessment does not include the specific chemical steps of photosynthesis and respiration.] HSSIC. A.1 Understand statistics as a process for making inferences about population parameters based on a random sample from that population. (HS‐LS2‐6) Bell Work 1. Discuss the history and importance of the chrysanthemum. 2. Explain the classifications of chrysanthemums. 3. Describe how chrysanthemums are propagated. 4. Identify major chrysanthemum pests and disorders, as well as controls. Terms Center bud removal Chrysanthemum Disbudding Grading cuttings Hard pinch Response group Roll out pinch Soft pinch Interest Approach Look at the plants and/or pictures in front of you. What do these plants remind you of? Are these planted around your house or yard? Have you seen these in flower arrangements? Do these plants come in a variety of shapes, sizes, and colors? Think about your answers to these questions as you follow this lesson. What is the history and importance of the chrysanthemum? Chrysanthemums, commonly referred to as mums, have their origin in China, Japan and Europe. Up until the 1940s, chrysanthemums were grown in the United States primarily as garden plants. Since then, they have been grown widely as cut flowers and potted flowering plants. Chrysanthemums are photoperiodic and thermoperiodic. Chrysanthemums rank second to poinsettias in terms of the number of pots sold in the United States. A chrysanthemum in flower What are the classifications of chrysanthemums? Chrysanthemums are classified based on their response group, plant height, and flower forms. Response group refers to the number of weeks it takes for the chrysanthemum to flower from the time they begin receiving short day treatments. Response groups range from 6 weeks to 15 weeks. Most potted chrysanthemums fall into the 9-week or 10-week response groups. Chrysanthemum varieties are classified as being short, medium or tall. Short varieties grow less than 15” in height. Medium varieties grow around 15” in height. Tall varieties grow more that 15” in height. Chrysanthemums are grouped in one of nine major flower forms including standard, spray, button, spoon, decorative, daisy, spider, pompon, and anemone. How are chrysanthemums propagated? Chrysanthemums are propagated asexually by stem cuttings. A few major companies produce 95% of the cuttings used in commercial production. Those companies provide rooted or nonrooted cuttings free of viral disease. Steps to propagating chrysanthemums are as follows: Take cuttings 2 to 3 inches in length with three leaves. Treat the cutting with a mediumstrength rooting hormone. Unrooted cuttings covered with rooting hormone “Stick” the cuttings and place under an intermittent mist system. Maintain bottom heat between 70 and 75º F. Light the cuttings to maintain vegetative growth. Fast rooting cuttings form roots in about 18 days. What is a growing schedule for a potted chrysanthemum crop? In preparing a production schedule, first determine the sale date. Then count back the number of weeks the plant requires short day treatment and another 2 weeks for vegetative growth. The quality of the crop often hinges on the care taken at planting time. Grade cuttings or sort them according to the number of roots, the diameter of the stem, and the length of the stem before potting. This ensures uniform growth in each pot. Use a growing medium with a pH between 6.0 and 6.5. Plant cuttings shallow and angle them outwards over the lip of the pot at about 45º angle. The most important stage of growth is the vegetative stage. Strong roots and reserves of sugars must be established. Fertilize at a rate of 250-350 parts per million nitrogen at the first watering. Drop the rate to 200-300 parts per million nitrogen and potassium with following waterings. Provide 65 to 70º F night temperatures and 75 to 80º F day temperatures. Maintain vegetative growth by interrupting the darkness by lighting between 10:00 p.m. and 2:00 a.m. Grow the plants until the roots appear at the bottom of the pots, then pinch to produce a well-branched plant with many flowers. • Use a roll out pinch or the removal of just the tip of the stem in winter. Three Methods of Pinching Roll-out Soft Hard • Use a soft pinch or the removal of ½ to ¾ inch of the stem and leaving five to six leaves. • Use a hard pinch to remove all but three or four leaves in the summer. • Flower bud initiation is accomplished by turning off the lights to provide a short day treatment. Covering the crop with black cloth might be necessary to simulate short day conditions. • Lower temperatures to 62 to 65º F at night. • Reduce fertilizer rates to 200-250 parts per million nitrogen and potassium. The flower bud development stage focuses on forming the flower buds. Drop night temperatures to 60 to 62º F. Fertilize at a rate of 200 to 250 parts per million nitrogen and potassium. Perform disbudding or the removal of selected developing flower buds to improve overall quality. Disbudding of all the lateral buds results in larger terminal flowers. Center bud removal involves pinching off the terminal flower bud. Finishing is the final stage and it involves preparing a plant for sale. Lower the greenhouse temperature to 55-58º F at night to increase flower color intensity. Stop fertilization and allow the media to dry slightly. What are major mum pests and diseases and their means of control? Chrysanthemums have both pests and disorders that require attention. The major pests include aphids, whiteflies, leaf miners, spider mites, cutworms and cabbage loopers. An IPM program should be followed to reduce pest problems. Aphids White Flys Leaf Miner Spider Mite Cut Worm Cabbage Looper The major diseases include botrytis, mildews, Pythium, Rhizoctonia, and Phytophthora. Proper watering and controlling humidity levels reduces disease problems. Review/Summary What is the history and importance of the chrysanthemum? What are the classifications of chrysanthemums? How are chrysanthemums propagated? Review/Summary Cont. What is a growing schedule for a potted chrysanthemum crop? What are major mum pests and diseases and their means of control? The End!