Horsetail (Equisetum spp)
Main sources: Florida
Taxon Lift: Sphenopsida
Horsetail is a member of the ancient
Sphenopsid clade, which is a sister to the Ferns, both
groups first appearing during the Carboniferous Period
(350-290 mya) of the Paleozoic Era. Unlike most of the early land
plants (except for the Lycopodia, ancestors of todays "Club
Mosses"), both these clades have living representatives,
though today's variety and prominence is much reduced from Paleozoic
times. Horsetail shows the typical Sphenopsid features: node/node
morphology (joint-to-joint construction of stems), whorled
arrangement of parts, reduced leaves, ridged and grooved stems,
"hollow" stems with a large, empty pith cavity, terminal
cones containing spores, and clonal rhizomes. Fossil Sphenopsids
called Calamites reached 30 feet in height during the Carboniferous
Period, and were prolific, judging by their fossil presence in
the coalbeds dated to that time.
Today, Horsetails reach only 2 to 5 feet high.
They are consistently found in riparian locations where their
rhizomes are in contact with saturated soil, and can produce colonies
of aerial stems. We see the plant in our Saguaro Juniper area
particularly in Hot Springs Canyon where the stream is perennial,
above the Zig Zag bend (and it may be spreading downstream along
with recovery of other riparian plants above the Yellow
Horsetail produces silica in its epidermis,
by virtue of which some varieties are called "Scouring Rush"
(the plant being used as a cleansing abrasive.) Medicinally, it
has been widely used around the world since ancient times for
a wide variety of ailments (just search the Web under "Horsetail"
for an endless variety of contemporary examples).
It can be very toxic to horses. For
a detailed diagram and description of plant characteristics, see
this link: Purdue
U. School of Veterinary Medicine Website.
to Trees & Shrubs