Emex australis Steinh.
Rumex hypogaeus (synonym Emex australis), commonly known in English as southern threecornerjack, devil's thorn, or double gee (also doublegee, from the old Afrikaner name dubbeltge-doorn - 'double thorned'), is a herbaceous plant of the Polygonaceae. It is native in South Africa and is an invasive species in Australia, Texas in the USA & Pakistan.
It grows to heights of from 10 to 60 cm and its stems may be prostrate, decumbent, or ascending. The base is often reddish. The leaves are stalked and without any surface covering, with the leaf blade being 1-10 by 0.5-6 cm. There are 1 to 8 flowers with stamens per sheathed bundle and these flowers have narrow oblong tepals which are 1.5-2 mm. The female flowers occur as groups of 1 to 4 per sheathed bundle, and the outer tepals are ovate to oblong and 4-6 mm in fruit, while the inner tepals are broadly triangular and , 5-6 mm in fruit. The achenes (dry 1-seeded fruits not opening at maturity) are 4-6 by 2-3 mm, and shiny.
It flowers all year round.
Distribution and habitat
Common names in Australia, where it is a weed, include: bindies, spiny emex, doublegee, double gee, double-gee, three corner jack, three-cornered jack, goat's head burr, goathead, jackie, prickly jack, cape spinach, devil's face, devil's thorn, bullhead, bull head, and cat's head.
Small infestations and isolated plants of Rumex hypogaeus can be dug out. When plants are seeding then they should be destroyed by burning. Control programs work best when all plants are killed shortly after having emergence, and should continue for several years.
- "Rumex hypogaeus T.M.Schust. & Reveal | Plants of the World Online | Kew Science". Plants of the World Online. Retrieved 2020-07-06.
- "Emex australis". Natural Resources Conservation Service PLANTS Database. USDA. Retrieved 18 January 2016.
- BSBI List 2007 (xls). Botanical Society of Britain and Ireland. Archived from the original (xls) on 2020-09-24. Retrieved 2014-10-17.
- "Emex australis in Flora of North America @ efloras.org". www.efloras.org. Retrieved 2020-07-06.
- "Weeds Australia Profile: Emex australis". profiles.ala.org.au. Retrieved 2020-07-11.
- Parsons, W.T & Cuthbertson, E.G. (2001). Noxious weeds of Australia. Victoria: CSIRO Publishing.CS1 maint: multiple names: authors list (link)
- Jepson Manual Treatment
- Distribution map showing where it is native and where introduced
- Rumex hypogaeus occurrence data from GBIF
- Emex australis Profile, photo gallery, distribution
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