Rhamnus cathartica

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Rhamnus cathartica
Illustration of Rhamnus catharticus 63-cropped.png
Common buckthorn
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Rosales
Family: Rhamnaceae
Genus: Rhamnus
Subgenus: Rhamnus
Species: R. cathartica
Binomial name
Rhamnus cathartica
L.
Synonyms[1]
  • Cervispina cathartica (L.) Moench
Fruit
Rhamnus cathartica - MHNT

Rhamnus cathartica (buckthorn, common buckthorn or purging buckthorn), is a species in the family Rhamnaceae, native to Europe, northwest Africa, and western Asia, from the central British Isles south to Morocco, and east to Kyrgyzstan.[2][3] It was introduced to North America as an ornamental shrub in the early 19th century or perhaps before.[4][5]

Description[edit]

Rhamnus cathartica is a deciduous shrub or small tree growing up to 10 m tall, with grey-brown bark and spiny branches. The leaves are elliptic to oval, 2.5–9 cm long and 1.2–3.5 cm broad; they are green, turning yellow in autumn, and are arranged somewhat variably in opposite to subopposite pairs or alternately. The flowers are yellowish-green, with four petals; they are dioecious and insect pollinated. The fruit is a globose black drupe 6–10 mm diameter containing two to four seeds; it is mildly poisonous for people, but readily eaten by birds, which disperse the seeds in their droppings.[6][7]

The species was originally named by Linnaeus as Rhamnus catharticus, but this spelling was corrected to cathartica as the genus name Rhamnus is of feminine gender.[8]

Toxicity[edit]

The seeds and leaves are considered toxic to humans and animals, causing stomach cramps and laxative effects thought to serve a function in seed dispersal. The chemical compounds responsible for this laxative effect are anthraquinone[9] and emodin.

In 1994 there was implication of R. cathartica in the outbreak of an idiopathic neurological disease in horses, though no causative agent was officially identified. In trials where rodents were fed the leaves and stems of R. cathartica, glycogen metabolism became abnormal and glycogen deposits formed in the cytoplasm of liver cells. Abnormalities in glycogen metabolism lead to diabetes in humans.[10]

Ecology[edit]

Rhamnus cathartica is shade-tolerant, moderately fast-growing and short-lived. It is a food plant of the Brimstone butterfly. The sulphur-yellow males are indicative of the plant's presence.

This species is the alternate host for the important rust disease of cereals caused by Puccinia coronata. R. cathartica is also the primary overwintering host in North America for an important agricultural pest of soybeans, the soybean aphid.[11]

Allelopathy[edit]

Secondary compounds, particularly emodin, have been found in fruit, leaves, and bark of the plant which may protect the plant from insects, herbivores, and pathogens.[12] Emodin present in R. cathartica fruit may serve purposes of prevention of early consumption, as it is found most in unripe fruits, which allows seeds to reach maturity before being dispersed. Birds and mice significantly avoid eating unripe fruits, and if forced to ingest emodin or unripe fruit, the animals regurgitate the meal or produce loose, watery stools.[12]

Allelopathic effects of exudates from R. cathartica leaf litter, roots, bark, leaves, and fruit may reduce germination of other plant species in the soil. Soils in buckthorn dominated areas are higher in nitrogen and carbon than normal soils, which speed up decomposition rates of leaf litter.[13] This can result in bare patches of soil being formed and R. cathartica performs well in such disturbed habitats, so this may be adaptive for the setting of its seed.[12]

Invasive species[edit]

In North America[edit]

The species is naturalised and invasive in parts of North America.[3][14][12] R. cathartica has a competitive advantage compared to native trees and shrubs in North America because it leafs out before native species.[15] The early emergence of their leaves in the spring and can shade out the growth of native plants. 27-35% of the annual carbon gain in R. cathartica comes from photosynthesis occurring before the leaves of other plants emerge. [9] Soil in woodlands dominated by R. cathartica was higher in nitrogen, pH, and water content than soil in woodlands relatively free of R. cathartica,[16][17] probably because R. cathartica has high levels of nitrogen in its leaves and these leaves rapidly decompose.

R. cathartica is also associated with invasive European earthworms (Lumbricus sp.) in the northern Midwest of North America.[18] Removing R. cathartica led to a decrease of invasive earthworm biomass of around 50%.[19]

Uses[edit]

A cutting board made from common buckthorn and Norway maple.

The bark and fruit were used as a purgative in the past, though their potentially dangerous violent action and side effects means they are now rarely used.[20]

The wood is hard and dense, but little-used.

Control methods[edit]

It is difficult to control because it sprouts vigorously and repeatedly from the root collar following cutting, girdling, or burning.[21] Herbicide application to newly cut stumps is a popular and effective control method. However, seeds stay viable in the soil for several years before sprouting, so repeated treatments and long-term monitoring of infested areas is required.[22] Garlon and Tordon, as well as their derivatives, have been found to be effective chemical means. Roundup can be used but is less reliable. [9] An application of these chemicals in early winter reduces the risk of negatively impacting non-target species, as most have gone dormant by this time. It is also easier to spot infestations at this time of the year, as its leaves stay out an average of 58 days longer than native plants.[9]

Mechanical control methods such as pulling and chopping of plants are more environmentally friendly, but also very time consuming. Plants with stems less than half an inch in diameter or less than a meter tall can easily be pulled, but pulling risks disturbing the roots of adjacent, native plants and harming them as well.[22] Propane-weed torches may also be used to kill seedlings and they will generally not re-sprout if burned in spring or early summer.[9]

References[edit]

  1. ^ "The Plant List: A Working List of All Plant Species". 
  2. ^ Flora Europaea: Rhamnus cathartica
  3. ^ a b Germplasm Resources Information Network: Rhamnus cathartica
  4. ^ Torrey J (1824) A flora of the northern and middle sections of the United States: or, a systematic arrangement of all the plants hitherto discovered in the United States north of Virginia. vol 1. T. and J. Swords, New York, pp. 513
  5. ^ Possessky SL, Williams CE, Moriarty WJ (2000). "Glossy Buckthorn, Rhamnus frangula L.: a threat to riparian plant communities of the northern allegheny plateau (USA)". Natural Areas Journal 20: 290–292. 
  6. ^ Rushforth, K. (1999). Trees of Britain and Europe. Collins ISBN 0-00-220013-9.
  7. ^ Flora of NW Europe: Rhamnus cathartica
  8. ^ Bean, W. J. (1980). Trees and Shrubs Hardy in the British Isles 8th ed., vol. 3. John Murray ISBN 0-7195-2427-X.
  9. ^ a b c d e Gale, Samuel (2000). "Control of the invasive exotic Rhamnus cathartica in temperate North American forests". Restoration and Reclamation Review 6: 1–13. 
  10. ^ Lichtensteiger, C; Johnston, N., Beasley, V. (1997). "Rhamnus cathartica (buckthorn) hepatocellular toxicity in mice". Toxicologic Pathology 25: 449–452. doi:10.1177/019262339702500503. 
  11. ^ Ragsdale D, Voegtlin D, O’Neil R (2004). "Soybean aphid biology in North America". Annals of the Entomological Society of America 97: 204–208. doi:10.1603/0013-8746(2004)097[0204:sabina]2.0.co;2. 
  12. ^ a b c d Kathleen S. Knight, Jessica S. Kurylo, Anton G. Endress, J. Ryan Stewart, Peter B. Reich (2007). "Ecology and ecosystem impacts of common buckthorn (Rhamnus cathartica): a review". Biological Invasions 9: 925–937. doi:10.1007/s10530-007-9091-3. 
  13. ^ Heneghan, L; Fatemi, F., Umek, L., Grady, K., Fagen, K., Workman, M. (2006). "The invasive shrub European buckthorn (Rhamnus cathartica, L.) alters soil properties in Midwestern U.S. woodlands". Applied Soil Ecology 32: 142–148. doi:10.1016/j.apsoil.2005.03.009. 
  14. ^ Minnesota Department of Natural Resources: Buckthorn - Invasive Species
  15. ^ Barnes WJ (1972) The autecology of the Lonicera × bella complex. Dissertation, University of Wisconsin
  16. ^ Heneghan, L., Rauschenberg, C., Fatemi, F., Workman, M. (2004). "European buckthorn (Rhamnus cathartica) and its effect on some ecosystem properties in an urban woodland". Ecological Restoration 22 (4): 275–280. doi:10.3368/er.22.4.275. 
  17. ^ Liam Heneghan, Farrah Fatemi, Lauren Umek, Kevin Grady, Kristen Fagen, Margaret Workman (2006). "The invasive shrub European buckthorn (Rhamnus cathartica, L.) alters soil properties in Midwestern U.S. woodlands". Applied Soil Ecology 32: 142–148. doi:10.1016/j.apsoil.2005.03.009. 
  18. ^ Heneghan L, Steffen J, Fagen K (2007). "Interactions of an introduced shrub and introduced earthworms in an Illinois urban woodland: impact on leaf litter decomposition". Pedobiologia 50: 543–551. doi:10.1016/j.pedobi.2006.10.002. 
  19. ^ Michael D. Madritch and Richard L. Lindroth (2009). "Removal of invasive shrubs reduces exotic earthworm populations". Biological Invasions 11: 663–671. doi:10.1007/s10530-008-9281-7. 
  20. ^ Plants for a Future: Rhamnus cathartica
  21. ^ Barnes, Burton V. and Wagner Jr., Warren H. (2004) Michigan Trees ISBN 978-0-472-08921-5
  22. ^ a b "Common Buckthorn Glossy Buckthorn". USDA Forest Service. 

External links[edit]