Identifying Sunflower's Plant Growth Stages
Do the terms “full bloom” and “physiological maturity” mean anything to you? Of course they do. But do they mean exactly the same thing to everyone else reading this publication?
Nearly 15 years ago, two well-known sunflower researchers — J.F. Miller and A.A. Schneiter — developed something called “Description of Sunflower Growth Stages.” Miller, a USDA-ARS research geneticist, and Schneiter, a North Dakota State University agronomist, believed the sunflower community needed a set of descriptive standards for the various plant growth stages from emergence through maturity. They recognized that what one person meant by the terms “bud,” “full bloom” or “mature” did not always correspond closely with another’s definition. It was important, they felt, for sunflower researchers, producers and others to have a common basis of description when discussing the various sunflower plant growth stages.
Out of that came the descriptions corresponding with the photos on the next page. It’s apparent these growth stage identities — references like “V-3,” “R-5.2” or “R-8” — have yet to become commonplace coffee shop terminology; and it’s unlikely they’ll ever replace “bud” or “bloom” around the countryside. But they have become widely used among the research community as vehicles for apple-to-apple comparison of the sunflower plant’s development.
For the producer, familiarity with sunflower’s growth stage descriptions can be very useful when following research recommendations — two prime examples being insect economic thresholds or spray application timing and the estimating of yield reductions from hail damage. With that in mind, we felt it would be useful to include the descriptions and their corresponding photos in this issue of The Sunflower. We hope readers will retain these pages (as well as the article on page 18 regarding calculation of hail impact on yield) for reference during the 1995 growing season and beyond.
Just a couple more comments regarding these growth stage descriptions and photos:
Miller and Schneiter remind users that the total time required for development of a sunflower plant and the time between the various stages of development will depend upon both the plant’s genetic background and the growing season environment. “When determining the growth stage of a sunflower field, the average development of a large number of plants should be considered,” they write. “[However], this staging method can also be used for individual plants.”
Also, since some diseases can cause head discoloration, they urge using healthy, disease-free heads in stages R-7 through R-9 to determine plant development.
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