Horsetail weed of the week


Equisetum arvense  Field Horsetail  Field horsetail is part of the ancient genus Equisetum, which was the dominant plant group during the Carboniferous age more than 230 million years ago. Horsetail is easily recognised by its upright, fir tree-like shoots that appear in summer.

Rhizomes

Horsetail is an invasive, deep-rooted weed with fast-growing rhizomes (underground stems) that quickly send up dense stands of foliage.  A primitive spore-bearing plant in the family Equisetaceae.  Horsetail spreads by spores or creeping rhizomes and tubers.  Rhizomes and tubers are spread with cultivating equipment, and through this mechanism they can infest nurseries quickly. The creeping rhizomes of this pernicious plant may go down as deep as 2m (7ft) below the surface, making them hard to remove by digging out, especially if they invade a border. They often enter gardens by spreading underground from neighbouring properties or land. Fleshy tubers grow along the underground rhizomes singly or in pairs, and are positioned from a few inches to six feet deep in the soil. They store carbohydrates produced by photosynthesis, allowing field horsetail to have amazing regenerative capability and making it difficult to control.

rhizomes equisetum

 Fertile spore-bearing shoots

In spring, fertile light brown stems, 20-50cm (10-20in) tall, appear with a cone-like spore producing structure at the end of the stems. In summer, sterile green shoots develop into fir tree-like plants, 60cm (2ft) tall. Although the absence of apparent leaves, which are represented by toothed scaly sheaths at the joints renders its shading affect comparatively unimportant, its filching of soil nutrients is considerable. The freely branched furrowed green stems feel harsh with a rough flinty covering. These over ground shoots are developed from hairy blackish stems ramifying below the soil sometimes to a depth of several metres and bearing numerous ovoid dark tubers which are readily detached and commonly re-establish this weed. Two types of stems grow from the rhizome annually. The fertile stems are off-white, 10–25 cm tall and 3–5 mm diameter, with 4–8 whorls of brown scale leaves, and an apical brown spore cone 10–40 mm long and 4–9 mm broad. Un-branched brownish shoots bearing several scaly whorls and ending in a cone of many shield like structures grow in early spring, resembling short asparagus sprouts, up to a foot tall.

equisetum close up spores

They are leafless, topped by a spore-bearing cone that can be up to four inches long. Since they lack chlorophyll, they die shortly after releasing a cloud of dust like spores.  they require a film of moisture on their surface to permit fertilisation of the female cells being effected by the free swimming male sperms which are liberated from other individuals. When the fertilised egg develops it becomes another horsetail, which forms cone bearing shoots in spring and branched barren shoots in summer.

wequisetum arvense sexual generation

Sterile shoots

The sterile stems are 10–90 cm tall and 3–5 mm diameter, with jointed segments around 2–5 cm long with whorls of side shoots at the segment joints; the side shoots have a diameter of about 1 mm. Some stems can have as many as 20 segments.

equisetum stem

Sterile stems arise after the fertile stems die back. These stems are grooved and hollow, covered with whirls of feathery leaves that make it look like a green bottlebrush or a miniature conifer, and persist through the summer until the first autumn frosts. horsetails have a very high diploid number of 216 (108 pairs of chromosomes). The specific name arvense is derived from the Latin arvensis, meaning “from the meadow, field or grassland.”

equisetum arvense stand

(http://en.wikipedia.org/wiki/Equisetum_arvense)

Field horsetail is found growing in landscape beds, fields, wooded areas and along roadsides. the prevalence of horsetail in fields where the surface of the soil is likely to be very moist in the earlier months of the year is associated with the alteration of generations referred to , since once the perennial spore-bearing generation is established it appears to be comparatively indifferent to soil conditions. Therefore, whilst it is often found in moist soils, it can grow well in drier places once established, and is a common problem in gravelly soils along roadsides and railroad tracks. Field horsetail contains high levels of silica, giving rise to another common name: scouring rush; it also makes it toxic to livestock. In cross section the hollow structure can be clearly seen.

equisetum cross section

Controlling Field Horsetail

Control options include repeated mowing or mechanical removal. Although it can take years, dedicated removal of sterile stems depletes the carbohydrate reserves and will eventually exhaust the rhizome. Field horsetail grows best in full sun, and can also be controlled by shading. Mechanical removal of the stems followed by mulching with black plastic can also be effective. Tillage can make the problem worse by spreading the rhizomes and/or tubers. Removing horsetail by hand is difficult. Although rhizomes growing near the surface can be forked out, deeper roots will require a lot of excavation. Shallow, occasional weeding is not effective and can make the problem worse, as the plant can regrow from any small pieces left behind. However, removing shoots as soon as they appear above the ground can reduce infestation if carried out over a number of years.

If horsetail appears in lawns, it can be kept in check by mowing regularly.

Chemical controls

Infestations of horsetail can be weakened with weedkiller.

  • On vacant soil, where there are no herbaceous perennials, bulbs or crops, you can use Bayer Ground Clear Weedkiller containing glyphosate/flufenacet/metosulam to inhibit new shoots
  • Tough weedkillers containing glyphosate (e.g. Scotts Roundup Ultra 3000, Scotts Tumbleweed, Bayer Tough Rootkill, Bayer Garden Super Strength Weedkiller or Doff Maxi Strength Glyphosate Weedkiller or for spot treatment use Scotts Roundup Gel) can be applied in late summer when growth is strong. Before using, bruise the shoots with a rake to ensure effective (https://www.rhs.org.uk/advice/profile?PID=257)

USES

The fronds of horsetail a persistent weed of badly drained soils and lawns are covered with tiny crystals of silica . This makes them quite abrasive and they were once used for polishing pewter and arrow shafts ( Mabey ,2010). They were also used as a fine grade sandpaper for cabinetmakers (Salisbury 1961). Horsetail is a member of the Equisetaceae family; the sole survivor of a line of plants going back three hundred million years. It is a descendant of ancient plants that grew as tall as trees during the carboniferous period of prehistoric times and members of this family gave rise to many of our coal deposits. Since being recommended by the Roman physician Galen, several cultures have employed horsetail as a folk remedy for kidney and bladder troubles, arthritis, bleeding ulcers, and tuberculosis. The Chinese use it to cool fevers and as a remedy for eye inflammations such as conjunctivitis and corneal disorders, dysentery, flu, swellings and haemorrhoids. (http://www.herbwisdom.com/herb-horsetail.html). Horsetail, or Equisetum arvense, is an herb that has historically been used as a diuretic to make you urinate more frequently. Diuretics affect the kidneys, increasing the amount of water and salt that are released into the urine. For people with kidney problems or edema (when the body holds onto fluid), getting rid of unwanted fluid and salt can be an important part of treatment. (http://www.healthline.com/health/does-horsetail-help-you-pee).

  1. Hyde, H. A., Wade, A. E., & Harrison, S. G. (1978). Welsh Ferns. National Museum of Wales ISBN 0-7200-0210-9.
  2.  Flora of North America: Equisetum arvense
  3.  Bebbington, A. “Toxicity of Equisetum to Horses”. Retrieved 1 December 2010. 
  4. ^ Howard, Michael. Traditional Folk Remedies (Century, 1987); p.159-160
  5. (http://oregonstate.edu/dept/nursery-weeds/weedspeciespage/horsetail/Equisetum_arvense_horsetail.html).
  6. (http://en.wikipedia.org/wiki/Equisetum_arvense)
  7. (https://www.rhs.org.uk/advice/profile?PID=257)
  8. (http://extension.psu.edu/plants/green-industry/news/2012/weed-of-the-month-field-horsetail-equisetum-arvense)
  9. Sir Edward Salisbury 1961 Weeds and Aliens New Naturalist Collins London
  10. Richard Mabey 2010 Weeds Profile books London 2010
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