''Juncus ingens'', common name giant rush, is a

dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...

perennial with horizontal or ascending

rhizomes In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...

. 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 An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

is large and drooping, with many flowers scattered along fine branchlets. Flowers occur mostly October-January, seeds are shed mostly December-April. ''Juncus ingens'' was first described by

Norman Wakefield Norman Arthur Wakefield (28 November 1918 – 23 September 1972) was an Australian teacher, naturalist, paleontologist and botanist, notable as an expert on ferns. He described many new species of plants. Wakefield was born in Romsey, Victori ...

in 1957. It is one of only two known dioecious species of ''Juncus'' native to Australia, the other being '' Juncus psammophilus''. ''Juncus ingens'' is native to the floodplains of southeastern

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

, occurring mainly in

Victoria Victoria most commonly refers to: * Victoria (Australia), a state of the Commonwealth of Australia * Victoria, British Columbia, provincial capital of British Columbia, Canada * Victoria (mythology), Roman goddess of Victory * Victoria, Seychelle ...

, forming dense stands on the margins of seasonal wetlands. Giant rush is rarely grazed by introduced herbivores such as cattle or horses, or by native herbivores such as kangaroos, and is also resistant to fire. Although native to Australia, ''Juncus ingens'' is considered an invasive species in some areas such as

Barmah National Park The Barmah National Park, formerly Barmah State Park, is a national park located in the Hume region of the Australian state of Victoria. The park is located adjacent to the Murray River near the town of Barmah, approximately north of Melbourne ...

. 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. Specifically, reduced winter flooding levels and extended flooding into summer months promotes the spread of ''J. ingens''. Conversely, increasing winter and spring flood depth and duration, and reduction of unseasonal flooding limits the growth and spread of ''J. ingens'', allowing recolonisation of displaced species such as Moira grass (''

Pseudoraphis spinescens ''Pseudoraphis spinescens'', called spiny mudgrass or Moira grass is a Rhizome, rhizomatous and stoloniferous aquatic or semi-aquatic perennial Poaceae, grass, with ascending stems forming loose, floating mats in water to 1 m deep or more, or wit ...

'').

:Water regime for vigorous growth ::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."

References

External links

Atlas of Living Australia: ''Juncus ingens''

Flora of Victoria: ''Juncus ingens''
{{Taxonbar, from=Q15506325 Flora of Australia Flora of Victoria (Australia) ingens Dioecious plants