Question: Thanks so much for your answer about Eutrochium ID! I wanted to ask a follow-up question: Is capitulum on Joe …
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Question
Thanks so much for your answer about Eutrochium ID! I wanted to ask a follow-up question: Is capitulum on Joe Pye one of the small floral structures that makes up the bigger corymb? Would I need to dissect this structure to see the number of flowers, or in the case of this mature one, count the number of seeds to reflect the number of disk flowers? What I'm guessing is the capitulum is the structure in the white below. Thanks again, Phil
Answer
Dear philterfeed, the capitulum is the flowerhead that makes up the array near the summit of the stem. In this genus, it includes tubular disk flowers (with five tooth-like lobes at the top) surrounded by flat, involucral bracts. You have pictured one capitulum in the photograph. The flower number is the best indicator, and yes, they do need to be dissected (usually) or counted from above. The seed-like fruits are a good estimate, but sometimes one or more might not mature, so you can get a slightly lower count than the flowers in each capitulum (but generally it works as well as the flowers). Best wishes.
