It’s a little bit early for lateflowering thoroughwort (Eupatorium serotinum) to be in flower, but this native wildflower was flowering — profusely and in multiple spots — at the Indian River Lagoon Greenway when we visited on 8/11/2018. Also known as late boneset, it is shown above along the mangrove-lined wetland crossover bridge and below in an area from which the monoculture of Australian pines was recently removed just behind a sign made somewhat superfluous by the riot of vegetation.
This plant is in the same genus as the sometimes weedy native dogfennel (Eupatorum capillifolium). Both of these plants were flowering up a storm at Captain Forster Hammock Preserve near the wetland ponds at the entrance on 9-25-2009, and their size which dwarfed the nearby volunteers is memorialized in the first A Tale of 2 Eupatoriums post written on 8/22/2016. An earlier post on 10-16-2015 depicts both of these plants in flower at the Olso Riverfront Conservation Area.
Both of these members of the daisy/aster family, Asteraceae, have white disk florets, lack ray florets (petals), are herbaceous perennial plants, and flower during the late summer and fall.
The leaves of dogfennel are very delicate, finely divided, and feathery in appearance, as shown in the photo below taken at the Greenway.
When it flowers (and it was not yet in flower at the Greenway where we walked), dogfennel is quite pretty with diffuse branched panicles of creamy white, tiny flowers.
Its wind-borne seed can invade disturbed areas and can become a terrible weed in old fields, pastures, and disturbed places.
The leaves of late flowering thoroughwort, by contrast, are lance-shaped (lanceolate), long pointed, stalked, and toothed. The upper surface is smooth, and the lower surface is hairy with resinous dots. Note the two lateral veins roughly parallel to the midrib.
Its flowers are borne in dense terminal clusters (corymbs).
Late flowering thoroughwort grows in moist disturbed sites, moist open hardwoods, wet hammocks, and tidal marshes, as seen below at ORCA.
The wonderful white flowers make ID easy. The foliage is fairly distinctive and is pictured below at Pelican Island National Wildlife Refuge on 3-10-2018, where we saw it from atop the Overlook Tower when we visited in .
Late flowering thoroughwort usually produces a prolific amount of flowers late in the fall, is quite attractive to pollinators, and, since it often grows to be +6′ tall, could be a beautiful “backdrop” in a pollinator planning in your yard. Dogfennel may be a bit too weedy in habit for most landscapes.
Enjoy the Oslo Riverfront Conservation Area 