Field Horsetail

Scientific name: Equisetum arvense

Field horsetail vegetative stems

Field horsetail

Field horsetail vegetative stem

Field horsetail vegetative stem

Field horsetail

Field horsetail (note large rhizomes)

Field horsetail rhizome
  • Key characteristics
  • Biology
  • Impacts
  • Control
  • Further information

  • Colony-forming perennial grows from creeping rhizomes that penetrate deep into the soil
  • Asparagus-like fertile stems have 1-4 cm long cone-like structures at the stem tips which contain millions of spores. After spores are released the fertile stems die
  • Fertile stems are smaller and thicker than the vegetative stems, are brown and appear in spring
  • Vegetative, sterile stems grow after the fertile stems die down. They are erect, green and grooved, with bristle-like branches growing from the joints giving a Christmas tree-like appearance. The stems are hollow, jointed and up to 80 cm tall
  • Above ground stems die back each autumn and appear again in spring.

Origin

  • Native to most temperate regions of the Northern Hemisphere, including Europe, North America and Asia
  • Found along some North and South Island river beds.

Ecology

  • Herbaceous perennial plant which tends to grow in damper places
  • It has different sterile and fertile spore-bearing stems, growing from a perennial underground rhizomatous stem system
  • Fertile (reproductive) stems are produced in early spring and are non-photosynthetic
  • These are whitish to light brown, hollow, cylindrical, jointed, unbranched, leafless, about 8 mm in diameter and 15-20 cm long. Tips of fertile stems end in a yellowish to brownish cone (strobilus) about 12-30 mm long, which produces spores. Once spores have been produced, fertile stems wither and die, usually in early summer
  • Sterile (vegetative) stems start to grow after the fertile stems have wilted, and persist through summer until the first autumn frosts
  • Sterile stems are green, either erect or somewhat prostrate, 15-60 cm tall and composed of slender, grooved, hollow joints, which are 1-1.5 mm in diameter
  • Sterile stems look like miniature pine trees with their plume-like branches. Their appearance also explains the plant’s common name of ‘horsetail’
  • Deep-growing rhizomes are persistent and also produce 1 cm long nodules (turions) which can survive and grow long after the parent rhizome dies or is killed.

Dispersal

  • Spread by extensive rhizomes, and moved to new places in soil or gravel on machinery
  • Spores (seldom produced in NZ) are dispersed by wind & water
  • Can regrow from underground rhizomes and turions after the top growth has been killed by herbicides or cold weather.

  • Reduces crop yields drastically if present in sufficient quantity
  • Reduces yield of desirable pasture species although will not compete well with healthy pasture
  • Toxic to horses, sheep and cattle, according to overseas reports
  • High silica content can adversely affect teeth and gums of grazing stock
  • Can cause milk taint in dairy pastures
  • Invasive in wet places and extremely hard to control once established, being resistant to most herbicides
  • Forms dense stands in a wide range of damper habitats which can prevent the regeneration of other species
  • Blocks waterways, contributing to flooding and siltation
  • Field horsetail is listed in the National Pest Plant Accord and as such it is illegal to propagate and knowingly spread this plant.

  • Dig out and incinerate all plant parts and contaminated soil (this can be a difficult job as the rhizomes can penetrate to considerable depths)
  • Several herbicides including; MCPA (dimethylamine salt), activated amitrole, glyphosate and triclopyr can be used to control the top growth. Some will translocate to the rhizomes or roots more than others if conditions are right while others provide residual control in the soil which may inhibit regrowth. Read the herbicide label and only use herbicides which are suitable for the intended use, apply with either a knapsack or boom sprayer. Note that there are severe restrictions limiting herbicide use over and around waterways. For effective herbicide control many repeat applications will be required and should be applied before too much top growth appears
  • Horizons Regional Council’s downloadable brochure contains information on herbicide options for field horsetail in several different situations.