Ledum is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 name formerly widely recognised in the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Ericaceae

Ericaceae

The Ericaceae, commonly known as the heath or heather family, is a group of mostly calcifuge flowering plants. The family is large, with roughly 4000 species spread across 126 genera, making it the 14th most speciose family of flowering plants...

, including 8 species of evergreen

Evergreen

In botany, an evergreen plant is a plant that has leaves in all seasons. This contrasts with deciduous plants, which completely lose their foliage during the winter or dry season.There are many different kinds of evergreen plants, both trees and shrubs...

 shrub

Shrub

A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...

s native to cool temperate and subarctic regions of the Northern Hemisphere

Northern Hemisphere

The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

 and commonly known as Labrador Tea.

Reclassification into Rhododendron

Recent genetic

Genetics

Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

 evidence has shown that the species previously treated in this genus are correctly placed in the genus Rhododendron

Rhododendron

Rhododendron is a genus of over 1 000 species of woody plants in the heath family, most with showy flowers...

, 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
  Rhododendron neoglandulosum
  Rhododendron neoglandulosum is a species of rhododendron known by the common names western Labrador tea and trapper's tea. It is a common shrub of western North America from British Columbia to California to Colorado, where it grows in moist areas such as bogs and marshes...
  
  Harmaja
• Ledum groenlandicum = Rhododendron groenlandicum (Oeder
  Georg Christian Oeder
  Georg Christian Edler von Oldenburg Oeder was a German-Danish botanist, medical doctor, economist and social reformer. His name is particularly associated with the initiation of the plate work Flora Danica.-Life and work:Oeder was the son of a Bavarian parish minister, Georg Ludwig 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

Labrador tea

Labrador tea is a name commonly applied to three closely related species:* Rhododendron tomentosum ,...

. 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

Bog-laurel

Bog-laurel is an evergreen shrub of cold acidic bogs, in the family Ericaceae. It is native to north-eastern North America, from Newfoundland to Hudson Bay southwards....

 and Bog-rosemary

Bog-rosemary

Andromeda polifolia, commonly known as Bog-rosemary, is a heath found across northern parts of the Northern Hemisphere. It is the only member of its genus. Bog rosemary is only found in bogs in cold peat-accumulating areas....

, 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 bacterial infection caused by Borrelia, involved in the pathogenesis of Lyme Disease

Lyme disease

Lyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...

.