common horsetail

Equisetum arvense
young vegetative stems (Photo: Sheldon Navie)
 habit (Photo: Mellisa  Offord)
habit (Photo: Trevor James)
infestation (Photo: Trevor James)
vegetative stem (Photo: Trevor James)
close-up of four-angled branches (Photo: Mellisa  Offord)
close-up of older stem with whorled branches (Photo: Trevor  James)
Common horsetail
close-up of younger stem with developing branches (Photo: Trevor James)
habit with fertile stems (Photo: Trevor  James)
scouring rush horsetail (Equisetum  hyemale) has branchless vegetative stems (Photo: Sheldon  Navie)
dwarf horsetail (Equisetum scirpoides) is much smaller plant with branchless stems (Photo: Sheldon Navie)
Herb
Whorled
Reduced / Needle
No colour
Green

Schedule 1 Prohibited Matter Biosecurity Queensland must be notified within 24 hours Ph. 13 25 23

A mostly upright and long-lived plant re-growing each year from creeping underground stems. It produces two distinctly different types of stems, without obvious leaves, and does not have any true flowers. Its green "vegetative" stems are tall, thin, and produce several spreading branches at each of their joints. Its whitish or pale brown "fertile" stems are shorter, thicker, and topped with a cone-like reproductive structure. This reproductive structure (1-4 cm long) is greenish to brownish in colour and consists of numerous scale-like structures.

Common names 
Also known as: bottle brush, Bull pipes, corn horsetail, foxtail rush, Horse pipes, horsetail fern, joint grass, mare's tail, meadow pine, Paddock pipes,
Family 
Equisetaceae
Deciduous 
No
Flowering time 
Spring
Native/Exotic 
Exotic
Origin 
This species originated a very long time ago and is considered to be native to most of the temperate regions of the Northern Hemisphere. More specifically, it is native to North America, most of Europe and large parts of Asia.
Notifiable 
Yes
State declaration 
Category 1
Council declaration 
As per State Declaration
Known distribution 

Common horsetail (Equisetum arvense ) is not yet widely naturalised in Australia. It has been recorded from some parts of central New South Wales (i.e. in the Sydney and Moonan districts). It has also been collected from gardens in Tasmania, Victoria and Queensland.

Habitat 

Common horsetail (Equisetum arvense) prefers cooler and wetter climates in the temperate regions of Australia. It is a potential weed of open woodlands, grasslands, pastures, crops, roadsides, gardens, swamps, wetlands, waterways and the margins of other waterbodies.

Habit 

An upright (i.e. erect) and long-lived (i.e. perennial) plant usually growing 5-60 cm tall. Its aboveground parts are short-lived (i.e. annual) and re-grow each year from creeping underground stems (i.e. rhizomes) that can be up to several metres long.

Common horsetail (Equisetum arvense) is regarded as an environmental weed in New South Wales and as a potential environmental weed in the ACT, Victoria, South Australia, Western Australia and Tasmania. Though this species in not yet widely established in Australia, it has the potential to become a persistent weed of riparian areas, wetlands and other low-lying areas in the temperate regions of Australia that have an annual rainfall above 500 mm. When it becomes established in gardens and bushland areas it spreads quickly by creeping underground stems (i.e. rhizomes) and is difficult to eradicate.The only known occurrences of this species escaping cultivation and spreading into bushland in Australia have been in the Sydney and Moonan districts in New South Wales. Populations of common horsetail (Equisetum arvense) were reported to be infesting hundreds of square metres along creeklines at these sites.

Stem and leaves 

The stems are mostly upright (i.e. erect or ascending) but can sometimes trail along the ground at first before turning upwards (i.e. occasionally decumbent). These stems are conspicuously jointed and are of two distinct types. Most of the stems are "vegetative" (i.e. sterile). These are green in colour (5-60 cm tall and 1.5-5 mm thick) with small cup-shaped sheaths at their joints (i.e. nodes). They are hollow, grooved lengthwise (i.e. longitudinally), and produce groups (i.e. whorls) of thin branches (8-15 cm long and about 5 mm thick) that are sometimes mistaken for leaves. These branches are four-angled and usually emanate from each of the stem joints (i.e. nodes). The sheaths are actually the reduced, scale-like, leaves. They are green to dark-brown in colour, borne in clusters (i.e. whorls) of 6-18, and are fused together to form a small cylindrical or cup-shaped structure (5-8 mm long) topped with teeth that are 2-3 mm long. The second type of stem is whitish or pale brown in colour, shorter and somewhat thicker (up to 30 cm tall and 8 mm thick). These are known as "fertile" stems and bear reproductive structures at their tips. They are jointed and sheathed like the vegetative stems but lack the whorls of green branches.

Flowers and fruits 

Being closely related to the ferns, this plant does not produce true flowers or seeds. Instead it produces spores in a cone-like structure known as a strobilus. These structures (i.e. strobili) are borne at the tips of the 'fertile' stems and usually appear during early spring, before the 'vegetative' (i.e. sterile) stems. They are greenish, whitish or brownish in colour (1-4 cm long) with numerous stalked scale-like structures (i.e. sporangiophores) which bear the spores. The masses of minute spores are pale greenish to yellow in colour.

Reproduction and dispersal 

This plant reproduces vegetatively via long creeping underground stems (i.e. rhizomes) and rounded tubers, and also by large numbers of tiny spores.The creeping underground stems (i.e. rhizomes) and tubers enable colonies to spread laterally over time. They can also be dispersed longer distances by cultivation, soil disturbance or in dumped garden waste. The tiny spores are dispersed by wind and water.

Similar species 

Common horsetail (Equisetum arvense) is a very distinctive plant, however there are other species of horsetails (Equisetum spp.) that are similar. Most of these are not yet present in this country, but at least five other species (i.e. Equisetum hyemale, Equisetum palustre, Equisetum scirpoides, Equisetum bogatensis and Equisetum ramosissimum) have also become naturalised or have been grown here as garden plants (i.e. ornamentals).Common horsetail (Equisetum arvense) may also be confused with young she-oak trees (i.e. Casuarina spp. and Allocasuarina spp.). These native trees also have small green, jointed, branches that resemble leaves. However, these are not borne in whorls like those of common horsetail (Equisetum arvense). The she-oaks (Casuarina spp. and Allocasuarina spp.) also grow into much larger trees and eventually produce distinctive woody fruit.