However, an anonymous commenter (see Comments) pointed out that these plants were probably Helianthus simulans, common name muck sunflower. Although their leaves are narrow, they are wider than H. angustifolius. After more investigation and measuring leaf widths, I concluded that the commenter was correct. The sunflowers shown here are H. simulans.
The USF Plant Atlas characterizes H. simulans as "Not Native." Wunderlin states it is native to Louisiana, but has escaped cultivation and is now found throughout the southeast.
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Swamp sunflower; narrowleaf sunflower (Helianthus angustifolius, Asteraceae)
Native
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Another very similar species found on wet Florida roadsides is Helianthus simulans, which may be in your pictures.
ReplyDeleteHow to tell:
Plants short, < 1.5 m tall; leaves < 1 cm wide..... H. angustifolius
Plants robust, > 1.5 m tall; leaves > 1 cm wide..... H. simulans
Thanks, Anonymous. I'm fairly certain the species shown here is H. angustifolius. Although the plants seemed tall, they were probably less than 1.5 m tall. The narrow leaves were very rough, with margins rolled under (revolute). According to Wunderlin, the leaf margins of H. simulans are flat, and the species is considered rare.
ReplyDeleteThat's interesting -- perhaps this is one of those botanists' controversies.
ReplyDeleteI was speaking from the Flora of North America and Weakley's Flora which describe the leaves of H. simulans as "usually slightly revolute" and "often revolute" and do not use this to distinguish from H. angustifolia.
They describe it as "uncommon" in Florida but recently increasing across the SE generally.
Flora of NA also uses leaf width to distinguish:
H. angustifolia.....leaves 0.15–0.5(–1) cm wide
H. simulans.........leaves 0.7–4 cm wide
Hard to tell from a picture, but <0.5cm is a VERY narrow average leaf width!