How to eat a Horsetail

Spring has arrived. The cheerful song of the American Robin wakes me up each morning, their is enough daylight for late afternoon frivolities, and the Western Chorus frogs are calling so jubilantly into the night now that they would put me to sleep if I wasn’t so excited to hear them. I open the window and cock my ear to the side to take in the sound that is occasionally audible over the constant grumble of the highway! In the woods the Bigleaf Maple flowers are popping out of their over-sized buds and the birches have given their last drops of sweet water. Like the leggy frogs that leap enthusiastically in the warm air after a winter burrowed in frigid mud, the plants too seem to be springing from the ground. Nettles grow visibly between my every-other day harvests and an often overlooking edible—Giant Horsetail—claims its place in the front of the seasonal line-up of tasty shoot vegetables.
In the Pacific Northwest we have several species of horsetail. Two are edible, three are useful as sandpaper, and the remaining are neither useful to humans, nor common (limited to sloughs and marshes). Following are descriptions of the edible species.
Giant Horsetail (Equisetum telmateia) description
Giant Horsetail is an herbaceous clonal species. New shoots emerge from an underground network of rhizomes beginning in early to mid-March. There are two types of shoots, the fertile (spore bearing) shoots appearing a week ahead of the vegetative shoots. Fertile shoots are ½-3/4” (1.5-2 cm) wide and 1-2’ (30-60 cm) tall. The stems elongate between nodes which are covered with papery brown bracts. At the top of each fertile shoot is a cone-like structure (strobilus) that changes from green to white and eventually matures to brown when it begins releasing spores. The vegetative shoots are slightly narrower and taller at 3/16-3/4” (5-20 mm) wide and 1.5-4’ (50-120 cm) tall. The nodes of the vegetative shoots are also surrounded by brown papery bracts, but they smaller giving room for the rings of needle like leave that give the plant its namesake appearance. The features that distinguish Giant Horsetail are most easily noticed in cross-section. A cross section of the vegetative shoots shows a large hollow center that is much wider than twice the thickness of the walls, and a cross section of the needle like leaves shows that they are rounded.

Edibility
Still OK (center); too old (right)
Perfect stage (left)
The fertile shoots of Giant Horsetails are best picked between March 15th and April 15th. At this time they are 4-8” (5-10 cm) tall and the cones are still whitish. Before this time they are hard to see and too small to be worth the effort, and after this time they become stringy. Palatability plummets after the cones brown. Pluck shoots at ground level and carefully peel off the coarse bract that surrounds each node. These bracts are filled with silicates that will sand away at your teeth, an anti-herbivory adaptation that usually keeps the deer from eating them unless they are really hungry. Once you have peeled the shoots, discard the strobilus, rinse off any dirt, and enjoy them fresh. Their mild flavor and juiciness is similar to celery, but they lack the annoying fibers. I didn’t learn to eat Giant Horsetails until nine years ago when my friend Trent picked one at the Outback Farm ate it. They have been among my favorite wild shoot vegetables ever since. 
Unprocessed vegetative shoots (left) and fertile shoots (right)
Perfectly ripe and peeled
The vegetative shoots of Giant Horsetail are also edible, but much more work for a product that is not as tasty. You must pick them before the needle like leaves have started to extend horizontally. Remove both the bracts (as above) and the leaves since the leaves contain the same silicate grazing defense as the bracts.
Ethnobotany
Closely related species often are used in very similar ways. Most Rubus fruits are choice edibles and most willows provide good withes for basket weaving. So too is the ethnobotany of horsetails. When I skimmed through Daniel Moerman’s “Native American Ethnobotany” I quickly realized that Indigenous societies across the continent traditionally use E. arvensisE. telmateia, and E. hymenale for similar things such as skin poultices, tonics for internal organs and sandpaper. However, a few accounts such suggest that the very coarse stems of Scouring Rush (E. hymenale) where traditionally eaten as medicine, and I suspect that this is a case of mistaken identity on the part of the ethnobotanist. The plants all share similar habitat and appearance, making identification without a reference specimen challenging. 
The fertile shoots of Giant Horsetail are traditionally pealed and eaten by Indigenous groups from the Yurok in California to the Nuu-chah-nulth on the West Coast of Vancouver Island, and several in between (Moerman). Further north along the coast, the plant is less common; while it is still recognized, it is apparently not eaten (see Turner 2010; Turner and Bell 1973). The Makah (Gill 1983), Nitinaht, Nuu-chah-nulth (Turner et al. 1983; but see Turner and Efrat 1872), and Clallam (Gunther 1973) eat both the fertile and vegetative shoots. The Makah also eat the young strobilus after boiling it for 10 minutes, and have a special name for the reproductive shoots that reflects the “head” on the top (Gill 1983). In earlier times, the tubers were evidently collected later in the season and eaten raw by the Makah (Swan 1870), Cowlitz, and Swinomish (Gunther 1973), or boiled and served with grease by the Makah, Clallam, Quinault, Cowlitz, and Lower Chinook (Gunther 1973; Fleisher 1980). The Cowlitz also pulverized the dried cones to mix with salmon eggs (Gunther 1973). The shoots are universally regarded as juicy and thirst quenching but I can find no descriptions of the taste of the tubers (and have not yet seen or tried them myself).
 
The name horsetail aptly reflects the similarity in appearance of the vegetative shoots to a horse’s tail. This resemblance is also captured in the genus name which means “horse bristle” in Latin. The species epithet comes from the Greek word telmat which means “wetland,” where the plants are often found. A geographically distinct subspecies of Giant Horsetail is found in Europe, Western Asia, and North Africa and retains the subspecies name telmateia whereas our western North American taxon goes by the subspecies name braunii (in honor of the German botanist Alexander Carl Heinrich Braun, 1805-1877, who specialized in spermophytes).
A week too late
Related species: Common Horsetail (Equisetum arvense)
Common Horsetails are widespread throughout North America. From a distance, they can be distinguished from Giant Horsetail by their smaller size, more kinked needles, and longer primary (inner most) leaf segments on each branch. In cross section, the needle like leaves are angled so strongly that they appear winged, and the void in the middle of the main stem is equal to or less than twice the wall thickness. The fastidious will also find that Giant Horsetails have 20-40 ridges around the stem while the Common variety have 10-15. At harvest time, the shoot thickness and wall to central void ratio are the most discernible differences. Fertile shoots of Common Horsetail can be peeled and eaten in the same manner as Giant Horsetail. They are more work for less reward, and I find them to also be less tasty. The young vegetative shoots may well be edible as above, but frankly, I can’t see how they would be worth the trouble when the fertile shoots are available.