Equisetum xferrissii (after Ferris), a cross between E. hye-male and E. laevigatum, is the most common of the many Eq-
uisetum hybrids. it is intermediate between the parents with the lower portion of the stems evergreen as in E. hyemale and the upper deciduous as in E. laevigatum. Lower stem and upper stem sheath configurations and colorations respectively tend to match the parents as well. This Equisetum is found throughout canada and the united states except for the consistently hot and humid lower southeastern states.
Equisetum fluviatile (of rivers and streams), the water horsetail or water pipes, is characterized by thick creeping rhizomes that wander about underwater or in muddy swamps. The deciduous aerial stems have small branches and mature at 2 to 3 ft. (60 to 90 cm). The species needs to be confined, but a container of "pipes" sunk into the border of a pond is certain to attract attention in Zones 1 to 8. it is not an appropriate choice for hot summer areas.
Equisetum laevigatum (smooth, polished), the smooth scouring rush, is a deciduous 2-ft. (60-cm) spreader and the only North American endemic. It is found in Zones 3 to 8 from mid-America westward. The ridges are smooth with black-trimmed green sheaths. Look for it in open, wet exposures.
Equisetum myriochaetum (numerous long hairs) offers a prehistoric experience with 15- to 24-ft. (4.5- to 8-m) tall spires carrying layers of feathery, horizontally drooping branches. While usually found in large conservatories, this species is reputedly hardy in Zones 9 to 11. Sopping wet soil, structural support, and wind protection would all be requirements.
Equisetum sylvaticum (of woods, sylvan), the woodland horsetail, is unusual in its preference for spreading throughout moist woods rather than the traditional inhospitable wet and exposed sites of other horsetails. Branches that subdivide (it is
Equisetum sylvaticum stands as a sentinel in the Jessen garden.
the only Equisetum to do this) extend in rather graceful whorls from square-cut rust-colored sheaths. In North America this 2-footer (60 cm) is native to Canada, dipping occasionally into the northern tier of the United States. Worldwide it is native to Europe, Asia, and Japan. Interested growers should give it a container, moisture, and shade in Zones 2 through cool summer 8.
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