Horsetails: State Prohibited Weed	LC0375
Keith Turnbull Research Institute, Frankston

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Common name

Horsetails, scouring rushes

Scientific name

Equisetum spp.

Family Equisetaceae

Equisetum is the single genus in the family, a group of primitive, non-flowering plants, allied with clubmosses, quillworts and ferns - all of which lack flowers and fruit, and produce large numbers of spores, rather than seeds. There are about 35 world species of Equisetum.

. Figure 1 (left). Common horsetails on sale at a market.	. Figure 2 (right). Young vegetative shoot of common horsetails, showing the tiny leaves united into a ringed sheath at each node.
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Status

Equisetum species are proclaimed as State Prohibited Weeds in Victoria. This means that Equisetum spp. are to be eradicated from the State. Equisetum spp. are proclaimed weeds throughout Australia except for NT and ACT, while E. arvense is proclaimed in ACT. Horsetails are not known to be naturalised in Victoria but have been on sale at Victorian nurseries and markets. They are present in some gardens, particularly in association with ponds and other water features.

Figure 3. Common horsetails, showing the cones at the ends of fertile stems.

Origin

The genus is almost cosmopolitan in distribution, with only Australia and New Zealand lacking native species. All Equisetum species present in Australia are believed to have been imported for ornamental or medicinal horticulture.

Description

Primitive spore-bearing, perennial herbs, mostly favouring wet places. The long, rhizomatous roots produce at close intervals numerous erect, grooved and ridged, jointed, hollow stems, with whorls of usually very small, green or brownish leaves united at the base into a sheath that encircles the stem at each node. Spore-producing cones are borne at the ends of the main stems. The number of leaves equals the number of stem ridges. The different species range in height from a few cm up to 10 m. Some die back in summer.

Stems – erect, hollow, segmented and finely grooved; sometimes with solid side-branches arranged in whorls arising from the joints between segments (ie. from the nodes). The segmentation is similar to that in she-oaks, Casuarina spp. Stems break easily at the joints between segments. Fertile stems, bearing cones, are produced before sterile stems. The two stem types may be similar or dissimilar in appearance.

Leaves – usually scale-like, united at the margins to form a toothed sheath that encircles the stem at each node (similar to Casuarina).

Reproductive structures – spores borne in cones at the ends of fertile stems and sometimes on the branches; spores dust-like, green to yellowish.

Roots – underground stems (rhizomes) which divide frequently, spread many metres horizontally and may descend to depths well over one metre. Tubers may be present.

The group has a complicated taxonomy and nomenclature, and individual species may be difficult to identify. The following species have been detected in Australia or are likely to be detected in the future:

E. arvense L., common or field horsetail. Native to temperate areas of the northern hemisphere and a weed in Europe, North America, South America, Asia, Africa and New Zealand. Naturalised in Qld, NSW and Tas, present in gardens in Victoria and sold at markets.

E. bogotense Kunth. Native to Central and South America.

E. debile Roxb. ex Vaucher (E. ramosissimum subsp. debile). Tropical and sub-tropical species occurring from India to Taiwan, New Guinea and Fiji. A potential threat to northern Australia.

E. hyemale L. (E. hiemale), scouring rush, greater horsetail. Native of most of Europe and widespread from Canada to Mexico. Infestations are on record in Tasmania and NSW. Recently detected under cultivation by herb growers and known from home gardens.

Equisetum palustre L., marsh horsetail. A weed in Europe, North America and Asia.

Equisetum ramosissimum Desf. (E.campanulatum Poir., Hippochaete ramosissima (Desf.) Borner), branched scouring rush, drill grass, mare’s tail, Transvaal horsetail. Native to Madagascar. A weed in Europe, North and South America and Asia. An infestation on record in northern NSW.

E. scirpoides Michx., dwarf horsetail. Northern Europe and North America.

Predictions based on climatic requirements and land characteristics indicate that at least E. arvense, E. palustre and E. ramosissimum could be highly invasive in Victoria.

Properties

Equisetum spp. are among the world’s worst agricultural weeds due to their resilience, toxicity and propensity to dominate poorly drained farmland and pastures. They have the potential to become persistent weeds of wetlands and other low-lying areas in southern Australia and are very difficult to control because of their extensive, inaccessible, underground parts. Chemical control may require soil sterilisation, while control by cultivation is often ineffective.

The high silica content of the shoots gives them a rough texture and makes them useful for scourers for cooking pots etc.

All species are thought to contain alkaloids toxic to livestock.

Horsetails reproduce mainly from rhizome fragments and spread mainly via the root system. The spores require prolonged moist conditions for germination and development and young sporophytes rarely survive.

Various medicinal uses have been reported.

Management

The Department of Primary Industries is responsible for the control of State Prohibited Weeds. Please provide details of any occurrences of Equisetum spp. to a Catchment Management Officer at a local office of the Department.

References

Blood, K. (2001) Environmental Weeds – A Field Guide for SE Australia. Mt Waverley, C.H. Jerram Science Publishers.

Holm, L.G., Plucknett, D.L., Pancho, J.V. and Herberger, J.P. (1977) The World’s Worst Weeds. Distribution and Biology. Honolulu, The University Press of Hawaii.

Parsons, W.T. and Cuthbertson, E.G. (1992) Noxious Weeds of Australia. Melbourne, Inkata Press.

Tutin, T.G. (1964) Equisetum. Pp. 6-8 in T.G. Tutin et al. (Eds.) Flora Europaea Volume 1. Lycopodiaceae to Platanaceae. London, Cambridge University Press.

Acknowledgements

Compiled by Ian Faithfull. Fig. 1 by Kate Blood, copyright 2001 CRC for Weed Management Systems. Figs. 2 and 3 by Michael Hansford.

This publication may be of assistance to you but the State of Victoria and its officers do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.