The Ericaceae are a family, commonly known as the heath or heather family, of flowering plants found most commonly in acid and infertile growing conditions. The family is large, with roughly 4000 species spread across 126 genera, making it the 14th-most-speciose family of flowering plants. The many well-known and economically important members of the Ericaceae include the cranberry, blueberry, huckleberry, azalea, rhododendron, and various common heaths and heathers (Erica, Cassiope, Daboecia, and Calluna for example).
The Ericaceae contain a morphologically diverse range of taxa, including herbs, dwarf shrubs, shrubs, and trees. Their leaves are usually alternate or whorled, simple and without stipules, and hermaphrodite flowers. The flowers show considerable variability. The petals are often fused (sympetalous) with shapes ranging from narrowly tubular to funnelform or widely bowl-shaped. The corollas are usually radially symmetrical (actinomorphic), but many flowers of the genus Rhododendron are somewhat bilaterally symmetrical (zygomorphic).
Distribution and ecology
Ericads have a nearly worldwide distribution. They are absent from continental Antarctica, parts of the high Arctic, central Greenland, northern and central Australia, and much of the lowland tropics and neotropics.
The family is largely composed of plants that can tolerate acidic, infertile conditions. Like other stress-tolerant plants, many Ericaceae have mycorrhizal fungi to assist with extracting nutrients from infertile soils, as well as evergreen foliage to conserve absorbed nutrients. This trait is not found in the Clethraceae and Cyrillaceae, the two families most closely related to the Ericaceae. Most Ericaceae (excluding the Monotropoideae, Pyroloideae, and some Styphelioideae) form a distinctive mycorrhizae, where fungi grow in and around the roots and provide the plant with nutrients. The Pyroleae tribe are mixotrophic and gain sugars from the mycorrhizae, as well as nutrients.
In many parts of the world, a "heath" or "heathland" is an environment characterised by an open dwarf-shrub community found on low-quality acidic soils, generally dominated by plants in the Ericaceae. A common example is Erica tetralix. This plant family is also typical of peat bogs and blanket bogs; examples include Rhododendron groenlandicum and Kalmia polifolia. In eastern North America, members of this family often grow in association with an oak canopy, in a habitat known as an oak-heath forest.
Some evidence suggests eutrophic rainwater can convert ericoid heaths with species such as Erica tetralix to grasslands. Nitrogen is particularly suspect in this regard, and may be causing measurable changes to the distribution and abundance of some ericaceous species.
In 2002, systematic research resulted in the inclusion of the formerly recognised families Empetraceae, Epacridaceae, Monotropaceae, Prionotaceae, and Pyrolaceae into the Ericaceae based on a combination of molecular, morphological, anatomical, and embryological data, analysed within a phylogenetic framework. The move significantly increased the morphological and geographical range found within the group. The resulting family now includes 9 subfamilies, 126 genera, and about 4000 species:
- Enkianthoideae Kron, Judd & Anderberg (one genus, 16 species)
- Pyroloideae Kosteltsky (four genera, 40 species)
- Monotropoideae Arnott (10 genera, 15 species)
- Arbutoideae Niedenzu (five genera, 80 species)
- Cassiopoideae Kron & Judd (one genus, 12 species)
- Ericoideae Link (19 genera, 1790 species)
- Harrimanelloideae Kron & Judd (one genus, two species)
- Styphelioideae Sweet (35 genera, 545 species)
- Vaccinioideae Arnott (50 genera, 1580 species)
The name Ericaceae comes from the type genus Erica, which appears to be derived from the Greek word ereike. The exact meaning is difficult to interpret, but some sources show it as meaning 'heather'. The name may have been used informally to refer to the plants in pre-Linnaean times, and was simply formalised when Linnaeus described Erica in 1753, and then when Jussieu described the Ericaceae in 1789.
- See the full list at List of Ericaceae genera.
Use in alternative medicine
Heather has been listed as one of the 38 plants used to prepare Bach flower remedies, a kind of alternative medicine promoted for its effect on health. However, according to Cancer Research UK, "there is no scientific evidence to prove that flower remedies can control, cure, or prevent any type of disease, including cancer".
- Angiosperm Phylogeny Group (2009). "An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III" (PDF). Botanical Journal of the Linnean Society 161 (2): 105–121. doi:10.1111/j.1095-8339.2009.00996.x. Retrieved 2013-07-06.
- Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008. http://www.mobot.org/MOBOT/research/APweb/
- Kathleen A. Kron, E. Ann Powell and J. L. Luteyn (2002). "Phylogenetic relationships within the blueberry tribe (Vaccinieae, Ericaceae) based on sequence data from MATK and nuclear ribosomal ITS regions, with comments on the placement of Satyria". American Journal of Botany 89 (2): 327–336. doi:10.3732/ajb.89.2.327. PMID 21669741.
- Watson, L., Dallwitz, M.J. (1992 onwards) The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 4th March 2011. http://delta-intkey.com.
- Keddy, P.A. 2007. Plants and Vegetation: Origins, Processes, Consequences. Cambridge University Press, Cambridge, UK. 666 p.
- Cairney, JWG & Meharg, AA (2003). "Ericoid mycorrhiza: a partnership that exploits harsh edaphic conditions". European Journal of Soil Science 54 (4): 735–740. doi:10.1046/j.1351-0754.2003.0555.x.
- Liu, Z.; Wang, Z.; Zhou, J.; Peng, H. (2010). "Phylogeny of Pyroleae (Ericaceae): implications for character evolution". Journal of plant research 124 (3): 325–337. doi:10.1007/s10265-010-0376-8. PMID 20862511.
- The Natural Communities of Virginia Classification of Ecological Community Groups (Version 2.3), Virginia Department of Conservation and Recreation, 2010
- Schafale, M. P. and A. S. Weakley. 1990. Classification of the natural communities of North Carolina: third approximation. North Carolina Natural Heritage Program, North Carolina Division of Parks and Recreation.
- Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. p.103-104.
- Kron, K.A., Judd, W.S., Stevens, P.F., Crayn, D.M., Anderberg, A.A., Gadek, P.A., Quinn, C.J., Luteyn, J.L. (2002). "Phylogenetic Classification of Ericaceae: Molecular and Morphological Evidence". The Botanical Review 68 (3): 335–423. doi:10.1663/0006-8101(2002)068[0335:pcoema]2.0.co;2.
- Wiktionary. 2011. Ericaceae. http://en.wiktionary.org/wiki/Ericaceae
- Jussieu, A.-L. de. 1789. Genera plantarum ordines naturales disposita. pg. 159-160. Herissant & Barrois, Paris.
- D. S. Vohra (1 June 2004). Bach Flower Remedies: A Comprehensive Study. B. Jain Publishers. p. 3. ISBN 978-81-7021-271-3. Retrieved 2 September 2013.
- "Flower remedies". Cancer Research UK. Retrieved September 2013.