Oclemena
Genus of flowering plants
From Wikipedia, the free encyclopedia
Oclemena is a genus of flowering plants in the tribe Astereae within the family Asteraceae. All species in the genus are native to eastern North America. The species were originally included in the genus Aster so they are often referred to simply as asters. Since their flower heads are nodding in bud, they are sometimes called nodding-asters.
| Oclemena | |
|---|---|
| |
| Oclemena nemoralis (bog aster) | |
Scientific classification  | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Asterids |
| Order: | Asterales |
| Family: | Asteraceae |
| Subfamily: | Asteroideae |
| Tribe: | Astereae |
| Subtribe: | Oclemininae G.L.Nesom |
| Genus: | Oclemena Greene[1] |
| Synonyms[2] | |
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Heterotypic synonyms
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Description
Oclemena species are perennial, herbaceous plants that propagate via a swollen tuber at the tip of a slender, elongated rhizome. Stems are erect and unbranched, with dense long hairs. Stem leaves are sessile (or short-petiolate) and alternate. Leaf blades are sparsely dotted with short glandular hairs, each with a yellow to orange resin head. Leaf margins are either serrate (O. acuminata) or both entire and revolute. The inflorescence is either a single flower head (O. nemoralis) or a corymb of 2–46 flower heads on long, slender peduncles, nodding in bud (except O. reticulata). A flower head has 7–25 ray flowers, white or pink, and 14–35 disc flowers, pale or pinkish yellow, reddening at maturity. The chromosome base number is x=9.[3][4][5]
| Oclemena acuminata | Oclemena nemoralis | Oclemena reticulata | |
|---|---|---|---|
| Plant height | 10–80 cm tall | 5–70 cm tall | 30–90 cm tall |
| Number of leaves | 11–18 Clustered at the summit of the stem |
30–100 Uniformly distributed along the stem |
12–30 Uniformly distributed along the stem |
| Leaf blades | 10–45 mm wide | 1–8 mm wide | 10–40 mm wide |
| Leaf margins | Prominently toothed with flat margins | Entire (or nearly so) and revolute | Entire (or toothed at the tip) and revolute |
| Flower heads | 5–46 | 1–15 | 9–40 |
| Ray flowers | 15 White or tinged with pink |
13–25 Pink to purple, seldom white |
7–11 White to pink |
| Disc flowers | 14–30 | 20–35 | 15–30 |
| Habitat | Forests | Bogs, fens, mossy lake shores | Seasonally moist sandy places, bogs, wet pine flatwoods |
The hybrid Oclemena × blakei is intermediate in appearance between its parents, Oclemena acuminata and Oclemena nemoralis.
Taxonomy
In 1903, the American botanist Edward Lee Greene established genus Oclemena by segregating two species, Aster acuminatus Michx. and Aster nemoralis Aiton.[3] Greene, initially drawn to this group of plants by the nodding habit of their flower heads in bud, had been using the name Oclemena acuminata on the labels of herbarium specimens since 1897. In 1995, the American botanist Guy L. Nesom segregated two additional taxa, Aster nemoralis var. blakei Porter and Aster reticulatus Pursh.[7] Nesom considered Oclemena to be monophyletic but closely related to Doellingeria Nees.[4] A major treatment of genus Oclemena appeared in Flora of North America in 2006:[5]
| Scientific name | Common name | Year described | Year published | Distribution |
|---|---|---|---|---|
| Oclemena acuminata (Michx.) Greene | whorled wood aster | 1803 | 1903 | Eastern Canada, Eastern United States |
| Oclemena × blakei (Porter) G.L.Nesom (O. acuminata × O. nemoralis) |
Blake's aster | 1894 | 1995 | Eastern Canada, Northeastern United States |
| Oclemena nemoralis (Aiton) Greene | bog aster | 1789 | 1903 | Eastern Canada, Northeastern United States |
| Oclemena reticulata (Pursh) G.L.Nesom | pinebarren whitetop aster | 1813 | 1995 | Southeastern United States |
As of December 2025[update], the generic name Oclemena Greene is widely accepted.[8][9][10][11]
Oclemena belongs to the North American clade of the tribe Astereae, as a basal member of one of its main branches.[12]
Distribution and habitat
Oclemena species are native to eastern North America.[5][13] Oclemena acuminata is the most wide-ranging species, from the Appalachian Uplands of Newfoundland to the southern tip of the Appalachian Mountains in the U.S. state of Georgia. In contrast, Oclemena reticulata îs restricted to the extreme southeastern United States where other species of Oclemena are not found. Oclemena nemoralis and Oclemena × blakei are boreal species that prefer the cold acidic bogs of eastern Canada and northeastern United States.
Gallery
