Juncus ingens

Juncus ingens, common name giant rush, is a dioecious perennial with horizontal or ascending rhizomes. The stems are erect, dull green, (1.5–2–5 m tall and 4–10 mm in diameter, cataphylls are to 40 cm or more long. The inflorescence is large and drooping, with many flowers scattered along fine branchlets. Flowers occur mostly October-January, seeds are shed mostly December-April.[1][2] Juncus ingens was first described by Norman Wakefield in 1957.[3]

Juncus ingens
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Clade: Commelinids
Order: Poales
Family: Juncaceae
Genus: Juncus
Species:
J. ingens
Binomial name
Juncus ingens

Juncus ingens is native to the floodplains of southeastern Australia, occurring mainly in Victoria,[4] forming dense stands on the margins of seasonal wetlands.[2] Giant rush is rarely grazed by introduced herbivores such as cattle or horses,[5] or by native herbivores such as kangaroos,[2] and is also resistant to fire.[2]

Although native to Australia, Juncus ingens is considered an invasive species in some areas such as Barmah National Park.[6][7] The spread of J. ingens into areas where it historically did not occur is a result of changes to flooding regimes in the now highly regulated Murray-Darling Basin.[5][8] Specifically, reduced winter flooding levels and extended flooding into summer months promotes the spread of J. ingens.[9][2][10][11] Conversely, increasing winter and spring flood depth and duration, and reduction of unseasonal flooding[12] limits the growth and spread of J. ingens,[9] allowing recolonisation of displaced species such as Moira grass (Pseudoraphis spinescens).[6]

Water regime for vigorous growth[2]
Maintenance:
Frequency of flooding: Annual to nearly annual.
Depth of flooding: Shallow, 5 to 50 cm; can tolerate up to 1 m.
Duration of flooding: Eight to 10 months
Timing of flooding: At least spring to early autumn.
Regeneration: Germination occurs on moist soil, bare of plants, such as on flood recession or wetland drawdown, in late autumn and winter.
Seedling establishment: Establishment is increased by shallow flooding, to 20 cm, in spring–early summer; and by avoiding stresses such as overtopping or droughting in the first two years.
Critical flood interval: Not certain. Maintains canopy in absence of flooding for a few years, but rhizomes probably persist longer; possibly reflood after about three to five years. Seed longevity not known."[2]

References
  1. Royal Botanic Gardens Victoria. "Flora of Victoria: Juncus ingens". Flora of Victoria.
  2. Roberts, Jane; Marston, Frances (2011), Water regime for wetland and floodplain plants: a source book for the Murray-Darling Basin (PDF), National Water Commission
  3. Wakefield, N. A. (1957). "Flora of Victoria: new species and other additions - 13". The Victorian Naturalist. 73 (12): 211–213.
  4. Atlas of Living Australia. "Juncus ingens : Giant Rush". bie.ala.org.au. Retrieved 28 April 2019.
  5. Chesterfield, E. A. (1986). "Changes in the vegetation of the river red gum forest at Barmah, Victoria". Australian Forestry. 49 (1): 4–15. doi:10.1080/00049158.1986.10674458.
  6. Ellery Mayence, C.; Marshall, David J.; Godfree, Robert C. (2010). "Hydrologic and mechanical control for an invasive wetland plant, Juncus ingens, and implications for rehabilitating and managing Murray River floodplain wetlands, Australia". Wetlands Ecology and Management. 18 (6): 717–730. doi:10.1007/s11273-010-9191-1. S2CID 42648770.
  7. Vivian, Lyndsey M.; Godfree, Robert (2012). J. R. Grove; I. D. Rutherford (eds.). The response of a degraded Murray River floodplain wetland to extreme drought and flood. Proceedings of the 6th Australian Stream Management Conference, Managing for Extremes, 6 – 8 February, 2012. Canberra: River Basin Management Society. pp. 1–7.
  8. Vivian, Lyndsey M.; Godfree, Robert C.; Colloff, Matthew J.; Mayence, C. Ellery; Marshall, David J. (2014). "Wetland plant growth under contrasting water regimes associated with river regulation and drought: implications for environmental water management". Plant Ecology. 215 (9): 997–1011. doi:10.1007/s11258-014-0357-4. S2CID 15896202.
  9. Stokes, Kate; Ward, Keith; Colloff, Matthew (2010). "Alterations in flood frequency increase exotic and native species richness of understorey vegetation in a temperate floodplain eucalypt forest". Plant Ecology. 211 (2): 219–233. doi:10.1007/s11258-010-9833-7. S2CID 20883741.
  10. Vivian, Lyndsey M.; Marshall, David J.; Godfree, Robert C. (2014). "Response of an invasive native wetland plant to environmental flows: Implications for managing regulated floodplain ecosystems". Journal of Environmental Management. 132: 268–277. doi:10.1016/j.jenvman.2013.11.015. PMID 24325821.
  11. Vivian, Lyndsey M.; Ward, Keith A.; Zwart, Alexander B.; Godfree, Robert C. (2014). Andy Sheppard (ed.). "Environmental water allocations are insufficient to control an invasive wetland plant: evidence from a highly regulated floodplain wetland". Journal of Applied Ecology. 51 (5): 1292–1303. doi:10.1111/1365-2664.12296.
  12. Ladson, Anthony R.; Chong, Joanne (2005). "Unseasonal flooding of the Barmah-Millewa forest". Proceedings of the Royal Society of Victoria. 117 (1): 127–137.
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