Scouringrush Horsetail, belonging to the only surviving genus of the Equisetophyta, is an incredibly aggressive vascular plant without seeds. While its method of spore production is not particularly efficient, the incredibly aggressive root system can spread rhizomes across very considerable distances (up to several meters, passing underneath greenhouses). These quickly form pure stands outcompeting other vegetation.
Equisetum hyemale (Scouringrush Horsetail, Common Horsetail)
Subspecies: subsp. affine, var. elatum, var. pseudohyemale
Native: almost all of North America, Guatemala, most of Asia (including Russia, even Siberia), most of Europe
Hardiness Zones: 4-9
Height: to roughly 1.5m
Diameter: cylindrical stems to 1cm in diameter
Root System: extensive
Growth Rate: rapid
Tolerates: deer grazing, virtually no pest problems, extremely tolerant of all soil types
Problems (major): none
Problems (minor): incredibly aggressive spreader
Poisonous: toxic if ingest in large quantities although not a substantial bioaccumulator (besides silica)
Soil requirements: prefers moist soils, native to wet soils, tolerates essentially any soil habit (including low pH, those with high concentrations of metals, highly disturbed sites)
Air requirements: appear to be tolerant of air pollution, at least that caused by mining
Watering requirement: moderate to high, possibly in standing water
Sun requirement: full sun to dense shade
Vascular tissue: present, conspicuous at nodes
Leaves: extremely reduced, (nearly vestigial) small, black structures at nodes, in whorls for all Equisetum sp.
Shoot: primary photosynthetic organ, erect, cylindrical, easily broken off just above nodes, jointed, rush/bamboo-like, contain large quantities of silicon, light-green (darker at internodes) to 1cm wide and 1.5m tall [fertile shoots pinkish-green, sometimes curved at top somewhat, short internodes, photosynthetic, to 30cm tall)
Roots: extensive rhizome system, possibly beyond 10 meters for mature, established colonies
Dominant generation: sporophyte
Gametophyte: nearly microscopic, thallus body similar to ferns with rhizoids (~roots/rhizomes), photosynthetic, to 4mm
Sporophyte: erect shoots, mostly hollow and cylindrical with supportive tissues at nodes
Strobili: typically terminal, spore-bearing, cone-like, elliptical, light orange with black spots, to 1cm
Horsetails are peculiar “fern allies” that phyllogenetically do not resemble angiosperms, gymnosperms, or bryophytes. Despite being the sole surviving genus, these plants can do remarkably well if given the opportunity.
These are commonly used in rain of water gardens, sometimes as a border. Be careful to not let these take over entire gardens! These have been previously used to scour pottery and wind instruments.
All of the images provided were taken by me. They may be used for educational/informational purposes only, provided that this article/online journal is appropriately cited first.