Senna artemisioides

Senna artemisioides, commonly known as silver cassia,^[2][3][4] is a species of flowering plant in the family Fabaceae and is endemic to Australia, where it is found in all mainland states and territories. It is a small, woody shrub with silver-green leaves and yellow flowers.

Silver cassia
Subspecies alicia in the West MacDonnell National Park
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Fabales
Family:	Fabaceae
Subfamily:	Caesalpinioideae
Genus:	Senna
Species:	S. artemisioides
Binomial name
Senna artemisioides (Gaudich. ex DC.) Randell^[1]
Synonyms^[1]
Cassia artemisiaefolia R.Br. orth. var. Cassia artemisioides Gaudich. ex DC.

Description

Senna artemisioides is a small shrub 1–3 m (3 ft 3 in – 9 ft 10 in) high with grey-green or silvery mostly pinnate leaves, leaflets in pairs of one to eight, variable, 2–4 cm (0.79–1.57 in) long, equal or increasing in size from the leaf base and sessile. The flowers are borne in clusters in leaf axils on a peduncle about 15 mm (0.59 in) long, 1.5 cm (0.59 in) in diameter, petals yellow, 4–10 mm (0.16–0.39 in) long, pedicel about 10 mm (0.39 in) long and the sepals 6–8 mm (0.24–0.31 in) long and greenish. Flowering occurs from April to November and the fruit is a linear-shaped pod 5–10 cm (2.0–3.9 in) long, 8–15 mm (0.31–0.59 in) wide, smooth, flattened and straight.^[2][5]

Taxonomy and naming

This species was first described in 1825 by Augustin Pyramus de Candolle, who gave it the name Cassia artemisioides in his Prodromus Systematis Naturalis Regni Vegetabilis,^[6] from an unpublished description by Charles Gaudichaud-Beaupré of specimens collected by Charles Fraser.^[7] In 1989 Barbara Rae Randell raised the genus Senna in the Journal of the Adelaide Botanic Gardens, and transferred C. artemisioides to the new genus as S. artemisioides.^[8][9] The Latin specific epithet (artemisioides) means "resembling Artemisia", a different group of plants often known as wormwood.^[10]

Senna artemisioides is known as wormwood senna in the U.K.,^[11] and as silver senna in the U.S., where it is an introduced species.^[12][13]

As of May 2023, the names of six subspecies of S. artemisioides are accepted by the Australian Plant Census:

• Senna artemisioides subsp. alicia Randell^[14] (N.T., S.A., Qld., N.S.W.) has cylindrical petioles, the leaves with up to three pairs of flat, silky-hairy, egg-shaped leaflets at least 2 mm (0.079 in) wide and held verticlly, exposing the lower surface.^[15][16][17]
• Senna artemisioides subsp. filifolia Randell^[18] (W.A., N.T., S.A., Qld., N.S.W., Vic.) has cylindrical petioles that are more than 15 mm (0.59 in) long, the leaves with up to four pairs of cylindrical leaflets 20–40 mm (0.79–1.57 in) long.^{[19][20][21][22]}
• Senna artemisioides subsp. helmsii (Symon) Randell (previously known as Cassia helmsii Symon) – blunt-leaved cassia^[23] (W.A., N.T., S.A., Qld., N.S.W.) has cylindrical petioles, the leaves with flat, woolly-hairy, egg-shaped leaflets at least 2 mm (0.079 in) wide.^[24][25][26]
• Senna artemisioides subsp. oligophylla (F.Muell.) Randell – blunt-leaved cassia^[27] (W.A., N.T., S.A., Qld., N.S.W.) has cylindrical petioles 5–15 mm (0.20–0.59 in) long, the leaflets egg-shaped, 10–40 mm (0.39–1.57 in) long and 10–20 mm (0.39–0.79 in) wide.^[28][29]
• Senna artemisioides subsp. quadrifolia Randell^[30] (N.T., S.A., Qld.) has cylindrical petioles 15–25 mm (0.59–0.98 in) long, the leaflets narrowly elliptic, 20–50 mm (0.79–1.97 in) long and 2–10 mm (0.079–0.394 in) wide.^[31][32]
• Senna artemisioides subsp. zygophylla (Benth.) Randell^[33] (S.A., Qld., N.S.W., Vic.) has cylindrical petioles, the leaves with flat, glabrous, linear to elliptic leaflets more than five times as long as broad.^[34][35][36]

Four hybrid subspecies are also recognised by the Australian Plant Census:

• Senna artemisioides (Gaudich. ex DC.) Randell subsp. × artemisioides (previously known as Cassia circinnata Benth.)^[37] (W.A., N.T., S.A., Qld., N.S.W., Vic.) has cylindrical petioles that are less than 15 mm (0.59 in) long, the leaves with three to eight pairs of cylindrical, hairy leaflets 15–25 mm (0.59–0.98 in) long, the edges rolled upwrds so that the upper surface is not visible.^{[38][39][40][41]}
• Senna artemisioides subsp. × coriacea (Benth.) Randell (previously known as Cassia sturtii var. coriacea Benth.)^[42] (W.A., N.T., S.A., Qld., N.S.W., Vic.) has cylindrical petioles, the leaves flat with up to six pairs of linear to elliptic leaflets that are sparsely hairy and glaucous, the leaflet held horizontally.^{[43][44][45][46]}
• Senna artemisioides subsp. × petiolaris Randell – woody cassia^[47] (W.A., N.T., S.A., Qld., N.S.W., Vic.) has petioles that are laterally compressed.^{[48][49][50][51]}
• Senna artemisioides subsp. × sturtii Randell (previously known as Cassia sturtii R.Br..)^[52] (W.A., N.T., S.A., Qld., N.S.W.) has cylindrical petioles, the leaves flat with linear to elliptic leaflets that are densely silky- or woolly-hairy, but never glaucous.^[53][54][55]

A further two supspecies are named, but as of May 2023, not formally described:

• Senna artemisioides subsp. James Range (P.L.Latz 18528) NT Herbarium^[56] (N.T.)^[57]
• Senna artemisioides subsp. Kuyunba (B.Pitts 113) NT Herbarium^[58] (N.T.)^[59]

Distribution

Silver cassia is endemic to Australia, occurring in all mainland states and territories, and has ben introduced to California, the Canary Islands, Cyprus, India, Iraq, Spain and Zimbabwe.^[13]

Ecology

S. artemisioides is a recognized larval food plant for several species of butterfly and moth, including the small grass yellow, icilius blue, twig looper, blotched satin moth and bag-shelter moth.^[60][61][62] Seed dispersal is aided by ants which eat the arils.^[63]

Use in horticulture

Senna artemisioides adapts to a wide range of climatic conditions, but is susceptible to frost, especially when young. It prefers dry, well-drained sites with full sun. As an ornamental plant, it is propagated readily from seed, which should first be briefly immersed in boiling water.^[64]

This species has gained the Royal Horticultural Society's Award of Garden Merit.^[11][65]

Images of subspecies

•  
  Subsp. filifolia in Currawinya National Park
•  
  Subsp. helmsii in West MacDonnell National Park
•  
  Subsp. oligophylla near Winton
•  
  Subsp. quadrifaria near Kata Tjuta
•  
  Subsp. zygophylla between Balranald and Robinvale
•  
  Subsp. × artemisioides in the Australian National Botanic Gardens
•  
  Subsp. × coriacea in South Australia
•  
  Subsp. x petiolaris between Narrandera and Morundah
•  
  Subsp. x sturtii South of Leigh Creek

References

1. "Senna artemisioides". Australian Plant Census. Retrieved 25 May 2023.
2. "Senna artemisioides". VICFLORA-Flora of Victoria. Royal Botanic Gardens Victoria. Retrieved 25 May 2023.
3. "Senna artemisioides". Australian Biological Resources Study, Department of Agriculture, Water and the Environment: Canberra. Retrieved 30 May 2023.
4. "Senna artemisioides group". Royal Botanic Garden, Sydney. Retrieved 30 May 2023.
5. Spooner, Amanda. "Senna artemisioides". FLORABASE-Flora of Western Australia. Department of Biodiversity, Conservation and Attractions. Retrieved 25 May 2023.
6. de Candolle, Augustin P. (1825). Prodromus Systematis Naturalis Regni Vegetabilis. Vol. 2. Paris. Retrieved 29 May 2023.
7. "Cassia artemisioides". Australian Plant Name Index. Retrieved 26 May 2023.
8. "Senna artemisioides". Australian Plant Name Index. Retrieved 26 May 2023.
9. Randell, B.R. (1989). "Senna artemisioides" (PDF). Journal of the Adelaide Botanic Gardens. 12 (2): 220. Retrieved 26 May 2023.
10. Harrison, Lorraine (2012). RHS Latin for Gardeners. United Kingdom: Mitchell Beazley. ISBN 978-1845337315.
11. "RHS Plant Selector - Senna artemisioides". Retrieved 5 March 2021.
12. USDA, NRCS (n.d.). "Senna artemisioides". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 10 November 2015.
13. "Senna artemisioides". Plants of the World Online. Retrieved 30 May 2023.
14. "Senna artemisioides subsp. alicia". Australian Plant Census. Retrieved 30 May 2023.
15. "Senna artemisioides subsp. alicia". Australian Biological Resources Study, Department of Agriculture, Water and the Environment: Canberra. Retrieved 30 May 2023.
16. Wiecek, Barbara. "Senna artemisioides subsp. alicia". Royal Botanic Garden Sydney. Retrieved 30 May 2023.
17. "Senna artemisioides subsp. alicia". Northern Territory Government.
18. "Senna artemisioides subsp. filifolia". Australian Plant Census. Retrieved 30 May 2023.
19. "Senna artemisioides subsp. filifolia". Australian Biological Resources Study, Department of Agriculture, Water and the Environment: Canberra. Retrieved 30 May 2023.
20. Wiecek, Barbara. "Senna artemisioides subsp. filifolia". Royal Botanic Garden Sydney. Retrieved 30 May 2023.
21. Jeanes, Jeff A.; Stajsic, Val. "Senna artemisioides subsp. filifolia". Royal Botanic Gardens Victoria. Retrieved 30 May 2023.
22. "Senna artemisioides subsp. filifolia". Northern Territory Government.
23. "Senna artemisioides subsp. helmsii". Australian Plant Census. Retrieved 30 May 2023.
24. "Senna artemisioides subsp. helmsii". Australian Biological Resources Study, Department of Agriculture, Water and the Environment: Canberra. Retrieved 30 May 2023.
25. "Senna artemisioides subsp. helmsii". Royal Botanic Garden Sydney. Retrieved 30 May 2023.
26. "Senna artemisioides subsp. helmsii". Northern Territory Government.
27. "Senna artemisioides subsp. oligophylla". Australian Plant Census. Retrieved 30 May 2023.
28. "Senna artemisioides subsp. oligophylla". Australian Biological Resources Study, Department of Agriculture, Water and the Environment: Canberra. Retrieved 30 May 2023.
29. "Senna artemisioides subsp. oligophylla". Northern Territory Government.
30. "Senna artemisioides subsp. quadrifolia". Australian Plant Census. Retrieved 30 May 2023.
31. "Senna artemisioides subsp. quadrifolia". Australian Biological Resources Study, Department of Agriculture, Water and the Environment: Canberra. Retrieved 30 May 2023.
32. "Senna artemisioides subsp. quadrifolia". Northern Territory Government.
33. "Senna artemisioides subsp. zygophylla". Australian Plant Census. Retrieved 30 May 2023.
34. "Senna artemisioides subsp. zygophylla". Australian Biological Resources Study, Department of Agriculture, Water and the Environment: Canberra. Retrieved 30 May 2023.
35. Wiecek, Barbara. "Senna artemisioides subsp. zygophylla". Royal Botanic Garden Sydney. Retrieved 30 May 2023.
36. Jeanes, Jeff A.; Stajsic, Val. "Senna artemisioides subsp. zygophylla". Royal Botanic Gardens Victoria. Retrieved 30 May 2023.
37. "Senna artemisioides subsp. × artemisioides". Australian Plant Census. Retrieved 30 May 2023.
38. "Senna artemisioides × artemisioides". Australian Biological Resources Study, Department of Agriculture, Water and the Environment: Canberra. Retrieved 30 May 2023.
39. Wiecek, Barbara. "Senna artemisioides × artemisioides". Royal Botanic Garden Sydney. Retrieved 30 May 2023.
40. Jeanes, Jeff A.; Stajsic, Val. "Senna artemisioides subsp. artemisioides". Royal Botanic Gardens Victoria. Retrieved 30 May 2023.
41. "Senna artemisioides subsp. artemisioides". Northern Territory Government.
42. "Senna artemisioides subsp. × coriacea". Australian Plant Census. Retrieved 30 May 2023.
43. "Senna artemisioides × coriacea". Australian Biological Resources Study, Department of Agriculture, Water and the Environment: Canberra. Retrieved 30 May 2023.
44. Wiecek, Barbara. "Senna artemisioides × coriacea". Royal Botanic Garden Sydney. Retrieved 30 May 2023.
45. Jeanes, Jeff A.; Stajsic, Val. "Senna artemisioides subsp. coriacea". Royal Botanic Gardens Victoria. Retrieved 30 May 2023.
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49. Wiecek, Barbara. "Senna artemisioides × petiolaris". Royal Botanic Garden Sydney. Retrieved 30 May 2023.
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54. Wiecek, Barbara. "Senna artemisioides × sturtii". Royal Botanic Garden Sydney. Retrieved 30 May 2023.
55. "Senna artemisioides subsp. sturtii". Northern Territory Government.
56. "Senna artemisioides subsp. James Range (P.L.Latz 18528) NT Herbarium". Australian Plant Census. Retrieved 30 May 2023.
57. "Senna artemisioides subsp. James Range (P.K.Latz 18528)". Northern Territory Government.
58. "Senna artemisioides subsp. Kuyunba (B.Pitts 113) NT Herbarium". Australian Plant Census. Retrieved 30 May 2023.
59. "Senna artemisioides subsp. Kuyunba (B.Pitts 113) NT Herbarium". Northern Territory Government.
60. Hunt, Lindsay; Grund, Roger; Keane, David; Forrest, Jan (2007). Attracting Butterflies to your Garden - What to Grow and Conserve in the Adelaide Redion (2nd ed.). Butterfly Conservation South Australia Inc. p. 143. ISBN 9780646955353.
61. McQuillan, Peter; Forrest, Jan; Keane, David; Grund, Roger (2019). Caterpillars, Moths and their Plants of southern Australia. Butterfly Conservation South Australia Inc. pp. 128, 144. ISBN 978-0-646-80648-8.
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