Rhododendron subsect. Ledum
| Rhododendron subsect. Ledum | |
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| Rhododendron tomentosum (Ledum palustre) | |
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Ledum is a genus name formerly widely recognised 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.
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.
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.
- Species
The species formerly listed in Ledum, with their current accepted names in Rhododendron, are:
- Ledum decumbens = Rhododendron subarcticum Harmaja
- Ledum glandulosum = Rhododendron neoglandulosum Harmaja
- Ledum groenlandicum = Rhododendron groenlandicum (Oeder) Kron & Judd
- Ledum hypoleucum = Rhododendron hypoleucum (Kom.) Harmaja
- Ledum macrophyllum = Rhododendron tolmachevii Harmaja
- Ledum palustre = Rhododendron tomentosum Harmaja
- Ledum palustre var. diversipilosum = Rhododendron diversipilosum (Nakai) Harmaja
- Ledum subulatum = Rhododendron subulatum (Nakai) Harmaja
- Hybrids
One natural hybrid also occurs:
- Ledum columbianum = Rhododendron × columbianum (R. groenlandicum × R. neoglandulosum)
Uses
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.
Ledum sp. often grows 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.
According to a Russian study from 1991, Ledum was able to almost completely inactivate the Tick-Borne indolent bacterial infection caused by the Genus Borrelia, some people believe to be involved in the pathogenesis of Lyme Disease which can lead to many chronic conditions.
References
1. Kron, Kathleen A. & Judd, Walter S. (1990) Phylogenetic Relationships within the Rhodoreae (Ericaceae) with Specific Comments on the Placement of Ledum Systematic Botany (1990), 1S(1): pp. S7-68
2. Harmaja, Harri (1990) New names and nomenclatural combinations in Rhododendron (Ericaceae) Ann. Bot. Fennici 27:203-204
3. Harmaja, Harri (1991) Taxonomic notes on Rhododendron subsection Ledum (Ledum, Ericaceae), with a key to its species. Ann. Bot. Fennici 28: 171-173.
6. Kihlman, Bengt A. (2004) Hybrids Between Ledums and Lepidote Rhododendrons. Journal of the American Rhododendron Society 58(2):74-81
7. Fokina, GI. Vopr Virusol, (1991) Experimental phytotherapy of tick-borne encephalitis,