Oclemena

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title: "Oclemena" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["astereae", "asteraceae-genera", "flora-of-northern-america", "taxa-named-by-edward-lee-greene"] description: "Genus of flowering plants" topic_path: "general/astereae" source: "https://en.wikipedia.org/wiki/Oclemena" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Genus of flowering plants ::

|image = Oclemena nemoralis, Pancake Bay PP.jpg |image_caption = Oclemena nemoralis (bog aster) |display_parents = 3 |parent_authority = G.L.Nesom |taxon = Oclemena |authority = Greene |synonyms = |Aster sect. Nemorali |House |Aster sect. Orthomeris |(Torr. & A.Gray) Benth. & Hook.f. |Aster subg. Orthomeris |(Torr. & A.Gray) A.Gray |Galatella sect. Calianthus |Nutt. |synonyms_ref =

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.

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.

::data[format=table]

Oclemena acuminata	Oclemena nemoralis	Oclemena reticulata
Plant height	10–80 cm tall	5–70 cm tall
Number of leaves	11–18
Clustered at the summit of the stem	30–100
Uniformly distributed along the stem
Leaf blades	10–45 mm wide	1–8 mm wide
Leaf margins	Prominently toothed with flat margins	Entire (or nearly so) and revolute
Flower heads	5–46	1–15
Ray flowers	15
White or tinged with pink	13–25
Pink to purple, seldom white
Disc flowers	14–30	20–35
Habitat	Forests	Bogs, fens, mossy lake shores
::

The hybrid Oclemena × blakei is intermediate in appearance between its parents, Oclemena acuminata and Oclemena nemoralis.

Taxonomy

::figure[src="https://upload.wikimedia.org/wikipedia/commons/7/78/Oclemena-acuminata01.jpg" caption="loc=[https://www.biodiversitylibrary.org/item/118189#page/440/mode/1up p. 432, Fig. 4352]}}"] ::

In 1903, the American botanist Edward Lee Greene established genus Oclemena by segregating two species, Aster acuminatus Michx. and Aster nemoralis Aiton. 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. Nesom considered Oclemena to be monophyletic but closely related to Doellingeria Nees. A major treatment of genus Oclemena appeared in Flora of North America in 2006:

::data[format=table]

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
::

, the generic name Oclemena Greene is widely accepted.

Oclemena belongs to the North American clade of the tribe Astereae, as a basal member of one of its main branches.

Distribution and habitat

Oclemena species are native to eastern North America. 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

| align = none | image_gap = 15 | image1 = Oclemena acuminata Vermont USA 2024-07-07.jpg | caption1 = Oclemena acuminata with nodding flower buds (July) | image2 = Oclemena nemoralis Quebec CA 2023-07-08.jpg | caption2 = Oclemena nemoralis with nodding flower bud (July) | image3 = Oclemena reticulata Florida USA 2025-03-22.jpg | caption3 = Oclemena reticulata with flower buds (March) | image4 = Oclemena acuminata New Hampshire US 2025-08-30.jpg | caption4 = Oclemena acuminata with flowers (August) | image5 = Oclemena nemoralis Quebec CA 2025-08-30.jpg | caption5 = Oclemena nemoralis with flowers (August) | image6 = Oclemena reticulata Florida US 2022-06-22.jpg | caption6 = Oclemena reticulata with flowers (June)

References

Bibliography

• Semple, J. C., S. Heard and Chunsheng Xiang, 1996. The Asters of Ontario (Compositae: Astereae): Diplactis Raf., Oclemena Greene, Doellingeria Nees and Aster L. (including Canadanthus Nesom, Symphyotrichum Nees and Virgulus Raf.). University of Waterloo Biology Series No. 30: 1-88.
• Semple, J. C., S. B. Heard and L. Brouillet. 2002. Cultivated and native asters of Ontario (Compositae: Astereae): Aster L. (including Asteromoea Blume, Diplactis Raf. and Kalimeris (Cass.) Cass.), Callistephus Cass., Galatella Cass., Doellingeria Nees, Oclemena E.L. Greene, Eurybia (Cass.) S.F. Gray, Canadanthus Nesom, and Symphyotrichum Nees (including Virgulus Raf.). University of Waterloo Biology Series No. 41: 1-134.

References

1. Brouillet, L., G.A. Allen, J.C. Semple, and M. Ito. 2001. ITS phylogeny of North American asters (Asteraceae: Astereae). Abstract. ''Botany 2001'', August 2001. Albuquerque, N.M.
2. {{BONAP. (2014)
3. (2025). "''Oclemena'' {{small". Compositae Working Group (CWG).
4. {{eFloras. 1. 122605. Oclemena
5. {{IPNI. Greene
6. "''Oclemena'' {{small".
7. {{PLANTS
8. "''Oclemena'' {{small".
9. "''Oclemena'' {{small".

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