Rhododendron subsect. Ledum

Ledum was a genus in the family Ericaceae, including 8 species of evergreen shrubs native to cool temperate and subarctic regions of the Northern Hemisphere and commonly known as Labrador tea. It is now recognised as a subsection of section Rhododendron, subgenus Rhododendron, of the genus Rhododendron.

Rhododendron subsect. Ledum
Rhododendron columbianum (Ledum glandulosum)
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Asterids
Order:	Ericales
Family:	Ericaceae
Genus:	Rhododendron
Subgenus:	Rhododendron
Section:	Rhododendron
Subsection:	Ledum (L.) Kron & Judd
Species
See text.

Description

Ledum species often grow together with poisonous plants such as bog-laurel and bog-rosemary, but certain species (e.g. L. groenlandicum and L. palustre) are easily distinguished by the distinctive rust coloured fuzz on the bottom of leaves.

Taxonomy

Reclassification into Rhododendron

Recent genetic evidence has shown that the species previously treated in this genus are correctly placed in the genus Rhododendron, where they are now treated as Rhododendron subsect. Ledum.[1] Because some of the species names used in Ledum could not be used in Rhododendron (the names already having been used for other species already in this large genus), new names had to be coined for them.[2]

Species

The species listed in genus Ledum (accepted and synonyms), with their current accepted names are:

Ledum species	Author	GBIF Status	TPL Status	GBIF Accepted species	Author	GBIF Status	TPL Accepted species	Author	TPL Status
Ledum	L.	Accepted[Ledum 1]
Ledum angustifolium	Hort. ex Lavallée	Accepted[Ledum 2]
Ledum buxifolium	Bergius		Synonym[Ledum 3]				Kalmia buxifolia	(Bergius) Gift & Kron	Accepted[Kalmia 1]
Ledum californicum	Kellogg		Synonym[Ledum 4]				Ledum glandulosum		Accepted[Ledum 5]
Ledum columbianum	Piper	Synonym[Ledum 6]	Accepted[Ledum 7]	Rhododendron columbianum	(Piper) Harmaja	Accepted[Rhody 1]
Ledum decumbens	(Ait.) Lodd.	Synonym[Ledum 8]		Rhododendron tomentosum subsp. decumbens	(Aiton) Elven & D.F.Murray	Accepted[Rhody 2]
Ledum decumbens	(Ait.) Lodd. ex Steud.	Synonym[Ledum 9]	Synonym[Ledum 10]	Rhododendron tomentosum subsp. decumbens	(Aiton) Elven & D.F.Murray	Accepted[Rhody 2]	Ledum palustre subsp. decumbens		Accepted[Ledum 11]
Ledum decumbens	Small	Accepted[Ledum 12]	Accepted[Ledum 13]
Ledum glandulosum	Nutt.	Synonym[Ledum 14]	Accepted[Ledum 5]	Rhododendron neoglandulosum	Harmaja	Accepted[Rhody 3]
Ledum glandulosum subsp. glandulosum			Synonym[Ledum 15]				Ledum glandulosum		Accepted[Ledum 5]
Ledum glandulosum var. californicum	(Kellogg) C.L.Hitchc.		Synonym[Ledum 16]				Ledum glandulosum		Accepted[Ledum 5]
Ledum glandulosum var. glandulosum			Synonym[Ledum 17]				Ledum glandulosum		Accepted[Ledum 5]
Ledum groenlandicum	Oeder	Synonym[Ledum 18]	Synonym[Ledum 19]	Rhododendron groenlandicum	(Oeder) K.A.Kron & W.S.Judd	Accepted[Rhody 4]	Ledum palustre subsp. groenlandicum		Accepted[Ledum 20]
Ledum groenlandicum	Retz.	Accepted[Ledum 21]
Ledum groenlandicum f. denudatum	Vict. & J.Rousseau	Accepted[Ledum 22]
Ledum groenlandicum subsp. glandulosum	(Nutt.) Á.Löve & D.Löve	Synonym[Ledum 23]	Synonym[Ledum 24]	Rhododendron neoglandulosum	Harmaja	Accepted[Rhody 3]	Ledum glandulosum		Accepted[Ledum 5]
Ledum groenlandicum var. aridiphilum	D.Löve	Accepted[Ledum 25]
Ledum hypoleucum	Kom.	Synonym[Ledum 26]	Synonym[Ledum 27]	Rhododendron diversipilosum	(Nakai) H.Harmaja	Accepted[Rhody 5]	Rhododendron hypoleucum	(Kom.) Harmaja	Accepted[Rhody 6]
Ledum idahoensis		Accepted[Ledum 28]
Ledum macrophyllum	Tolm.	Synonym[Ledum 29]	Accepted[Ledum 30]	Rhododendron diversipilosum	(Nakai) H.Harmaja	Accepted[Rhody 5]
Ledum maximum	(Nakai) A.P.Khokhr. & M.T.Mazurenko	Synonym[Ledum 31]	Accepted[Ledum 32]	Rhododendron tomentosum	Harmaja	Accepted[Rhody 7]
Ledum palustre	L.	Synonym[Ledum 33]	Accepted[Ledum 34]	Rhododendron tomentosum	Harmaja	Accepted[Rhody 7]
Ledum palustre	Michx.	Synonym[Ledum 35]		Rhododendron groenlandicum	(Oeder) K.A.Kron & W.S.Judd	Accepted[Rhody 4]
Ledum palustre f. decumbens	(Aiton) Y.L.Chou & S.L.Tung		Synonym[Ledum 36]				Ledum palustre subsp. decumbens		Accepted[Ledum 11]
Ledum palustre subsp. angustissimum	Worosch.	Synonym[Ledum 37]		Rhododendron subulatum	(Nakai) Harmaja	Accepted[Rhody 8]
Ledum palustre subsp. decumbens	(Aiton) Hultén		Accepted[Ledum 11]
Ledum palustre subsp. diversipilosum	Hara		Synonym[Ledum 38]				Ledum macrophyllum		Accepted[Ledum 30]
Ledum palustre subsp. groenlandicum	(Oeder) Hultén	Synonym[Ledum 39]	Accepted[Ledum 20]	Rhododendron groenlandicum	(Oeder) K.A.Kron & W.S.Judd	Accepted[Rhody 4]
Ledum palustre var. angustifolium	Hook.	Accepted[Ledum 40][lower-alpha 1]
Ledum palustre var. angustum	E.A.Busch		Synonym[Ledum 41]				Ledum palustre		Accepted[Ledum 34]
Ledum palustre var. decumbens	Aiton		Synonym[Ledum 42]				Ledum palustre subsp. decumbens		Accepted[Ledum 11]
Ledum palustre var. diversipilosum	Nakai	Synonym[Ledum 43]	Synonym[Ledum 44]	Rhododendron diversipilosum	(Nakai) H.Harmaja	Accepted[Rhody 5]	Ledum macrophyllum		Accepted[Ledum 30]
Ledum palustre var. latifolium	(Jacq.) Hook.	Synonym[Ledum 45]		Rhododendron groenlandicum	(Oeder) K.A.Kron & W.S.Judd	Accepted[Rhody 4]
Ledum palustre var. latifolium	(Jacq.) Michx.	Synonym[Ledum 46]		Rhododendron groenlandicum	(Oeder) K.A.Kron & W.S.Judd	Accepted[Rhody 4]
Ledum palustre var. maximum	Nakai		Synonym[Ledum 47]				Ledum maximum		Accepted[Ledum 32]
Ledum palustre var. palustre			Synonym[Ledum 48]				Ledum palustre		Accepted[Ledum 34]
Ledum palustre var. subulatum	Nakai		Synonym[Ledum 49]				Rhododendron subulatum	(Nakai) Harmaja	Accepted[Rhody 9]
Ledum serpyllifolium		Accepted[Ledum 50]
Ledum subulatum	(Nakai) A.P.Khokhr. & M.T.Mazurenko	Synonym[Ledum 51]	Synonym[Ledum 52]	Rhododendron subulatum	(Nakai) Harmaja	Accepted[Rhody 8]	Rhododendron subulatum	(Nakai) Harmaja	Accepted[Rhody 9]

Species References

Ledum

1. GBIF Secretariat, ed. (2016). "Ledum L." GBIF Backbone Taxonomy. Retrieved 2017-09-20.
2. GBIF Secretariat, ed. (2016). "Ledum angustifolium Hort. ex Lavallée". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
3. TPL Reference: group=Ledum name=tro-50176889 Coming soon
4. TPL Reference: group=Ledum name=tro-50092423 Coming soon
5. TPL Reference: group=Ledum name=tro-12300614 Coming soon
6. GBIF Secretariat, ed. (2016). "Ledum columbianum Piper". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
7. TPL Reference: group=Ledum name=tro-12300613 Coming soon
8. GBIF Secretariat, ed. (2016). "Ledum decumbens (Ait.) Loddiges". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
9. GBIF Secretariat, ed. (2016). "Ledum decumbens (Ait.) Loddiges ex Steudel". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
10. TPL Reference: group=Ledum name=kew-2349911 Coming soon
11. TPL Reference: group=Ledum name=kew-2355735 Coming soon
12. GBIF Secretariat, ed. (2016). "Ledum decumbens Small". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
13. TPL Reference: group=Ledum name=tro-12300073 Coming soon
14. GBIF Secretariat, ed. (2016). "Ledum glandulosum Nutt". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
15. TPL Reference: group=Ledum name=tro-12302631 Coming soon
16. TPL Reference: group=Ledum name=tro-12300615 Coming soon
17. TPL Reference: group=Ledum name=tro-12302504 Coming soon
18. GBIF Secretariat, ed. (2016). "Ledum groenlandicum Oeder". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
19. TPL Reference: group=Ledum name=kew-2349909 Coming soon
20. TPL Reference: group=Ledum name=kew-2355734 Coming soon
21. GBIF Secretariat, ed. (2016). "Ledum groenlandicum Retz". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
22. GBIF Secretariat, ed. (2016). "Ledum groenlandicum f. denudatum Vict. & J.Rousseau". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
23. GBIF Secretariat, ed. (2016). "Ledum groenlandicum var. aridiphilum D.Löve". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
24. TPL Reference: group=Ledum name=tro-50298977 Coming soon
25. GBIF Secretariat, ed. (2016). "Ledum groenlandicum var. aridiphilum D.Löve". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
26. GBIF Secretariat, ed. (2016). "Ledum hypoleucum Komarov". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
27. TPL Reference: group=Ledum name=tro-12303119 Coming soon
28. GBIF Secretariat, ed. (2016). "Ledum idahoensis". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
29. GBIF Secretariat, ed. (2016). "Ledum macrophyllum Tolm". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
30. TPL Reference: group=Ledum name=tro-12300074 Coming soon
31. GBIF Secretariat, ed. (2016). "Ledum maximum (Nakai) A.P.Khokhrjakov & M.T.Mazurenko". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
32. TPL Reference: group=Ledum name=tro-50194624 Coming soon
33. GBIF Secretariat, ed. (2016). "Ledum palustre L." GBIF Backbone Taxonomy. Retrieved 2017-09-20.
34. TPL Reference: group=Ledum name=kew-2349893 Coming soon
35. GBIF Secretariat, ed. (2016). "Ledum palustre Michx". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
36. TPL Reference: group=Ledum name=tro-50156076 Coming soon
37. GBIF Secretariat, ed. (2016). "Ledum palustre subsp. angustissimum Worosch". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
38. TPL Reference: group=Ledum name=tro-12303120 Coming soon
39. GBIF Secretariat, ed. (2016). "Ledum palustre subsp. groenlandicum (Oeder) Hulten". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
40. GBIF Secretariat, ed. (2016). "Ledum palustre var. angustifolium Hook". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
41. TPL Reference: group=Ledum name=tro-50156075 Coming soon
42. TPL Reference: group=Ledum name=kew-2355732 Coming soon
43. GBIF Secretariat, ed. (2016). "Ledum palustre var. diversipilosum Nakai". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
44. TPL Reference: group=Ledum name=tro-12303121 Coming soon
45. GBIF Secretariat, ed. (2016). "Ledum palustre var. latifolium (Jacq.) Hook". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
46. GBIF Secretariat, ed. (2016). "Ledum palustre var. latifolium (Jacq.) Michx". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
47. TPL Reference: group=Ledum name=tro-50194625 Coming soon
48. TPL Reference: group=Ledum name=tro-50156073 Coming soon
49. TPL Reference: group=Ledum name=tro-50194628 Coming soon
50. GBIF Secretariat, ed. (2016). "Ledum serpyllifolium". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
51. GBIF Secretariat, ed. (2016). "Ledum subulatum (Nakai) A.P.Khokhrjakov & M.T.Mazurenko". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
52. TPL Reference: group=Ledum name=tro-50194629 Coming soon

Rhododendron

1. GBIF Secretariat, ed. (2016). "Rhododendron columbianum (Piper) Harmaja". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
2. GBIF Secretariat, ed. (2016). "Rhododendron tomentosum subsp. decumbens (Aiton) Elven & D.F.Murray". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
3. GBIF Secretariat, ed. (2016). "Rhododendron neoglandulosum Harmaja". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
4. GBIF Secretariat, ed. (2016). "Rhododendron groenlandicum (Oeder) K.A. Kron & W.S. Judd". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
5. GBIF Secretariat, ed. (2016). "Rhododendron diversipilosum (Nakai) H. Harmaja". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
6. TPL Reference: group=Rhody name=tro-50303827 Coming soon
7. GBIF Secretariat, ed. (2016). "Rhododendron tomentosum Harmaja". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
8. GBIF Secretariat, ed. (2016). "Rhododendron subulatum (Nakai) Harmaja". GBIF Backbone Taxonomy. Retrieved 2017-09-20.
9. TPL Reference: group=Rhody name=tro-50223463 Coming soon

Other

1. TPL Reference: group=Kalmia name=tro-50310693 Coming soon

Hybrids

Natural hybrids (nothospecies) also occur.

• Ledum columbianum = Rhododendron × columbianum (R. groenlandicum × R. neoglandulosum) is listed by Harri Harmaja as a natural hybrid.[2]
• Rhododendron vanhoeffeni Abromeit[3] is a probably hybrid between Ledum palustre subsp. decumbens and Rhododendron lapponicum.[2]

Uses

Ledum (L. groenlandicum) essential oil in clear glass vial

Some species (e.g. L. groenlandicum) have been used to produce Labrador tea. Other species have varying levels of toxicity (e.g. L. glandulosum). Evergreen Labrador Tea grows slowly, but retains its leaves year-round. Users should take care not to over-harvest leaves from any single plant.

See also

• List of Sections in Subgenus Rhododendron

Notes

1. This is an inconsistency in GBIF data: the species name is a "Synonym" but a variety is "Accepted".

References

1. Harmaja 1991.
2. Kihlman 2004
3. GBIF Secretariat, ed. (2016). "Rhododendron vanhoeffeni Abromeit". GBIF Backbone Taxonomy. Retrieved 2017-09-21.

Bibliography

• Judd, Walter S. & Kron, Kathleen A. (2009). "Rhododendron Linnaeus, Sp. Pl. 1: 392. 1753; Gen. Pl. ed. 5, 185. 1754". Flora of North America. 8.
• Kron, Kathleen A. & Judd, Walter S. (1990). "Phylogenetic Relationships within the Rhodoreae (Ericaceae) with Specific Comments on the Placement of Ledum". Systematic Botany. 15 (1): 57–68. doi:10.2307/2419016. ISSN 0363-6445. JSTOR 2419016.
• Harmaja, Harri (1990). "New names and nomenclatural combinations in Rhododendron (Ericaceae)". Ann. Bot. Fennici. 27 (2): 203–204. JSTOR 23725435.
• Harmaja, Harri (1991). "Taxonomic notes on Rhododendron subsection Ledum (Ledum, Ericaceae), with a key to its species". Ann. Bot. Fennici. 28 (2): 171–173. JSTOR 23725406.
• Harmaja, Harri (1999). "Rhododendron diversipilosum, comb. nov. (Ericaceae)" (PDF). Ann. Bot. Fennici. 35: 263–264.
• Harmaja, Harri (2002). "Rhododendron subulatum, comb. nova (Ericaceae)" (PDF). Ann. Bot. Fennici. 39: 183–184.
• Kihlman, Bengt A. (2004). "Hybrids Between Ledums and Lepidote Rhododendrons". Journal of the American Rhododendron Society. 58 (2): 74–81.