Description
Horsetails (Equisetum spp.) are a primitive, non-flowering perennial plant related to ferns. There are 30 species world-wide, of which 12 are considered weedy. They produce two different kinds of shoots from long underground stems called rhizomes. The pale brown fertile fronds bearing fruiting cones emerge in spring and die after shedding spores. Sterile green, hollow branched shoots then develop. Both kinds of shoots break easily at the joints.
Inconspicuous leaves on the main shoots grow in rings of 6 to 18, joined at their edges to form a black-tipped sheath of sharp teeth around the stem. The Common Horsetail (E. arvense) shoots usually die back over winter. However, above ground growth may persist over the winter months in other species.
Scouring Rush Horsetail (E. hyemale) was given its common name due to the high silica content in the plant tissues. The shoots have been used to scour pots and pans (Weeds Australia).
For further information and assistance with identification of Horsetails contact the herbarium in your state or territory.
Distribution:
While Horsetails have been found in a number of sites from Tasmania to Brisbane they are thought to have only naturalised at this stage in New South Wales. Infestations have been recorded north of Sydney at Narrabeen Lakes, Belrose, and at Snake Creek, Bayview Heights, infesting hundreds of square metres along creek lines at these sites.
Scouring Rush Horsetail (E. hymenale) is naturalised in New South Wales in areas below altitudes of 620 m with annual rainfall of 1100-1500 mm. Branched Horsetail (E. ramosissimum) has become a weed in New South Wales by outgrowing the garden areas where it was planted. Outbreaks of Scouring Rush Horsetail and Branched Horsetail are currently under control.
Habit:
Herb, Aquatic
Key points:
- Horsetails (Equisetum spp.) are one of the world’s worst weeds.
- They are not native to Australia and have the capacity to damage both native biodiversity and agriculture if they become established.
- Horsetails are extremely invasive and difficult to control. Prevention and early intervention is the most effective control method.
- Despite their desirability for landscaping and herbal medicine they should not be planted in gardens.
- If this species is seen it should be reported the relevant weed management authority. Do not attempt to control on your own.
How it spreads:
Horsetails produce millions of tiny spores that are dispersed by wind and water. However, most of these spores do not survive as they require prolonged moist conditions (such as in wetlands) to germinate. Most of the spread of Horsetails occurs by rhizomes. A piece of the rhizome or tuber broken off the parent plant can grow into a new plant. As a result Horsetail fragments can easily be carried in soil or transported by construction equipment to new areas. They can also be distributed through the dumping of garden rubbish and contaminated soil, or during road making activities.
It is possible that Common Horsetail was introduced into New Zealand in the soil surrounding the roots of Iris commercially imported from Japan. The rhizomes of one individual can grow extensively, eventually reaching 30 m wide and up to 5 m deep although without soil disturbance this growth is relatively slow.
Where it grows:
Horsetails generally require moist conditions to establish but can then persist in a wide range of climates due to a number of adaptations which help to increase water use efficiency: a waterproof outer layer, green stems and special pores in the leaves. In drier areas the plants greatly reduce the size of their leaves to minimise water loss.
Most species inhabit swampy areas such as the edges of lakes, rivers and creeks, and prefer disturbed sites. They grow on many types of soil and can tolerate low nutrient levels. While they prefer wet areas they can move into well-drained soil through vegetative reproduction.
Common Horsetail (E. arvense) usually grows in damp, open woodlands, pastures, arable lands, roadsides, stream banks and embankments. It will grow in most wet places below altitudes of 300 m. It is a weed in Australia in areas where the annual rainfall is around 1400 mm.
Scouring Rush Horsetail (E. hyemale) similarly occurs on moist or springy grasslands, banks and roadsides, and is naturalised in New South Wales in areas below altitudes of 620 m with annual rainfall of 1100-1500 mm.
Flower colour:
No flower
Distribution map:
Impacts:
Horsetails are on the Alert List for Environmental Weeds, a list of 28 non-native plants that threaten biodiversity and cause other environmental damage. Although only in the early stages ofestablishment, Horsetails have the potential to seriously degrade Australia’s ecosystems.
Horsetails are known as one of the world’s worst weeds and are highly invasive. In Sydney they have infested hundreds of square metres along creek lines. They have the potential to become persistent weeds of wetlands and other low-lying areas. Large areas of natural vegetation are potentially under threat.
Horsetails are highly toxic to livestock. If consumed in contaminated hay it has been known to kill horses, cattle and sheep. In high densities, Horsetails reduce crop yields by producing inhibitory substances that depress the growth of neighbouring plants.Horsetails are of particular concern to the canola, cereals, lupin, apple and pear, and potato growing industries and as a nursery weed.
Origin:
This genus is mostly native to temperate regions of the northern hemisphere, although one species is found in Papuasia, as far south as New Guinea. Common Horsetail, the most common species found in Australia, is a native of Great Britain, Europe, Asia and North America.
