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SUNFLOWER DEVELOPMENT

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North Dakota State UniversityFargo, North Dakota 58105FEBRUARY 1998A-1145 Stages of Sunfl ower DevelopmentA.A. Schneiter, ProfessorJ.F. Miller, USDA-ARSD.R. Berglund, Extension AgronomistVegetative StagesR-5.1R-8 R-9R-7R-5.5 R-5.9 R-6True leaf — 4 cmV-EV-2V-4R-3 R-3 Top View R-4 Top ViewR-1 R-2Reproductive StagesV-12R-2 R-3More than 2cmLess than 2cmNDSU Extension Service, North Dakota State University of Agriculture and Applied Science, and U.S. Department of Agriculture cooperating. Duane Hauck, director, Fargo, N.D. Distributed in furtherance of the acts of Congress of May 8 and June 30, 1914. We offer our programs and facilities to all people regardless of race, color, national origin, religion, sex, disability, age, Vietnam era veterans status or sexual orientation; and are an equal opportunity employer. 2M-2-98, 1.5M-4-05This publication will be made available in alternative format upon request to people with disabilities (701) 231-7881.Description of sunfl ower growth stagesThe total time required for development of a sunfl ower plant and the time between the various stages of development depends on the genetic background of the plant and the growing environment. When determining the growth stage of a sunfl ower fi eld, the average development of a large number of plants should be considered. This staging method can also be used for individual plants. The same system can be used for classifying either a single head or branched sunfl ower. In the case of branched sunfl ower, make determinations using only the main branch or head. In stages R7 through R9, use healthy, disease-free heads to determine plant development if possible, because some diseases can cause head discoloration. Stage DescriptionVegetative Emergence VE Seedling has emerged and the fi rst leaf beyond the cotyledons is less than 4 cm long.Vegetative Stages V (number) These are determined by counting the number of true leaves at (i.e.) V1 least 4 cm in length beginning as V1, V2, V3, V4, etc. If senescence V2 of the lower leaves has occurred count leaf scars (excluding those V3 where the cotyledons were attached) to determine proper stage. etc.,Reproductive Stages R1 The terminal bud forms a miniature fl oral head rather than a cluster of leaves. When viewed from directly above the immature bracts form a many-pointed star-like appearance. R2 The immature bud elongates 0.5 to 2.0 cm above the nearest leaf attached to the stem. Disregard leaves attached directly to the back of the bud. R3 The immature bud elongates more than 2.0 cm above the nearest leaf. R4 The infl orescence begins to open. When viewed from directly above immature ray fl owers are visible. R5 (decimal) This stage is the beginning of fl owering. The stage can be divided (i.e.) R5.1 into substages dependent upon the percent of the head area (disk R5.2 fl owers) that has completed or is in fl owering. Ex. R5.3 (30%), R5.3 R5.8 (80%) etc. etc. R6 Flowering is complete and the ray fl owers are wilting. R7 The back of the head has started to turn a pale yellow color. R8 the back of the head is yellow but the bracts remain green. R9 The bracts become yellow and brown. This stage is regarded as physiological maturity.From Schneiter, A.A., and J.F. Miller. 1981. Description of Sunfl ower Growth Stages. Crop Sci. 21:901-903. For more information on this and other topics, see:


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