Stems procumbent or sometimes with erect branches, elongated, 4 to 10 dm, long, dark green, cylindrical ,4 to 7.5 cm, in diameter; ribs 12 or 13, broad and obtuse, divided into prominent. more or less distinctly 6 sided tubercles; areoles circular, felted; spines at first brown, some turning gray, others black; radial spines 6 to 8, acicular, somewhat spreading, 1 to 2 cm. long ; central spine solitary-, porrect, 2 to 4 cm. Long ;flowers white, about 20 cm. long, funnel form; outer perianth-segments greenish; axils of scales on flower-tube long-woolly; fruit about 5cm. long, hairy, red ,splitting on one side; seed black.

More or less branched above; trunk 4 to 6 meters high, cylindrical, 18 cm. in diameter; branches more or less curved, ascending, 5 to 8 cm. in diameter, obtuse at apex; ribs 15, low, obtuse, at first strongly tubercled by a strong depression between the areoles, but gradually disappearing in age; areoles small, circular, felted ;spines 8 to 10, yellow or brownish, setaceous short, 4 to 8 mm. long; flowers 20 to 24 cm. Long ,greenish without; inner perianth-segments oblanceolate acute, white; scales on the ovary and flower-tube hairy in their axils.

Stem upright, at first simple, later profusely branching at the base; branches ascending parallel with the main stem. (6 to 9 dm. high by 5 to 6 cm. in diameter, columnar; ribs 10 to 15, obtuse, rounded; areoles about 1 cm. apart, large, covered with curly yellow wool, becoming white; radial spines 8 to 10, 6 mm. to 1 cm. long, spreading, stiff, sharp, amber-yellow to brown ;central solitary, stronger and longer than the radials; all the spines later becoming gray; flowers about 20 cm. long by about 15 cm. in diameter, white.

Columnar, simple or branching at base, 1.5 to 2 meters high, 7 to 8 cm. in diameter; ribs 10 to 17, low and rounded; radial spines 11 to 14, acicular to subulate, 8 to 10 mm. long; central spines 4, 2 cm. long; Flowers funnel form, 20 to 24 cm. long; outer perianth-segments red; inner perianth-segments white, 2.5cm. long, acuminate

Plant often 6 to 10 meters high, sometimes less than 1 meter, usually either simple or with few branches and resembling a small Carnegiea gigantea ,sometimes with a number of branches from the base, more or less club-shaped, 3 dm. in diameter near the top, when old spineless at base; ribs 20 to 38, low, 2cm high; areoles large, approximate, sometimes touching one another; spines numerous, rather variable on young plants; spines yellow, stiff, subulate, the longer ones 4 to 14 cm. long: on old plants, especially flowering ones, elongated, flexible, sometimes bristle-like, 10 to 12 cm. long, yellow or even white; flowers 10cm.long, the ovary and tube covered with long brown hairs; fruit globular, about 3 cm. in diameter ;seeds small,dull black.

This species is very characteristic of the high plains on northern Argentina and Bolivia, sometimes growing in valleys, but usually along cliffs and on rocky hillsides, and often forms the most conspicuous plant in the landscape. The woody trunks are used for making goat corrals and rude huts. The fruit, which is said to b~ edible, is called pasacana.

Tall, 2 to 5 meters high, more or less branching, pale green, a little glaucous; branches 1 to 1.5 dm. in diameter, 4 to 8 ribbed: ribs obtuse, separated by broad but shallow intervals; areoles large, about 2 cm.apart; spines 2 to 6, yellowish, acicular to subulate, very unequal, sometimes 10 cm. long, not swollen at base; flowers large, 18 cm long; Flower tube 5 to 6 cm, long; throat broad; inner perianth segments oblong, perhaps white, 5 to 6 cm, long; scales on ovary and flower-tube small, sometimes only 3 to 4 mm long, scattered, bearing numerous hairs in their axils; fruit scaly, long-hairy, 5 to 6 cm. long.

Plants tall, 3 to 6 meters high, with numerous strict branches, slightly glaucous when young, dark green in age; ribs 6 to 8, broad at base, obtuse, with a deep horizontal depression above the areole; spines often wanting, when present few, 3 to 7, unequal, the longest 1 to 2 cm. long, dark yellow to brown; flower-buds pointed; Flowers very large, 19 to 23 cm. Long, borne near the top of branches, night-blooming, very fragrant; outer perianth-segments brownish red; inner perianth-segments oblong, white; filaments long, weak, greenish; style greenish below, white above; stigma-lobes linear, yellowish; ovary covered with black curled hairs; axils of scales on flower-tube and fruit bearing long black hairs.

Stem probably tall, stout, but in cultivation often slender, bluish green, especially on young growth; ribs usually 7, low and rounded, 1.5 cm. high, separated by acute intervals; areoles large, 1.5 to 2 cm. apart; spines several from an areole, acicular, brown; radial spines 5 to 8 mm. long; central spine about 2cm. long; flowers probably large and white; fruit unknown.

Plants tall, 5 to 6 meters high, much branched, the branches somewhat spreading, light green when young; ribs 7 or 8, low and rounded; areoles rather close together, 1 to l.5 cm. apart; spines numerous, often 12, very stout, rigid, sometimes 7 cm.long, swollen at base; Flowers 12 to 14 cm. long, doubtless nocturnal but, sometimes at least, remaining open during the morning, fragrant: Flower-tube green, 5 to 6 cm. long; inner perianth-segments oblong, white, 4 to 5 cm· long; filaments weak, declining on the ]ower side of the throat; scales on the ovary and flower-tube small, bearing a few long hairs in their axils

Plant 2 to 4 meters high with numerous erect or ascending, stout branches, 15 to 20 cm. In diameter, glaucous when young; ribs 6 to 8, broad and rounded; areoles large, 2 to 2.5 cm· apart, brown felted; spines brown from the first, about 10, unequal, some of them 4 cm. long, rigid and stout, not at all swollen at base; areoles on ovary and flower-tube hairy; mature Flowers not seen but evidently large and probably white.

This species resembles ~. bridgesii but has stouter and darker spines. It is found western slopes off the Andes at a much lower altitude than that species.

Stems rarely single, usually of several branches, sometimes of many, arising from near the base, starting nearly at right angles to the main trunk but soon erect, the tallest sometimes 8 meters high; ribs usually 16 or 17, low and broad, separated by narrow intervals, divided into large tubercles even when fully mature; radial spines when young light yellow with brown tips but soon becoming gray, 8 to 12, slightly spreading, often stout, 1 to 2 or even 4 cm. long; central spine single, porrect, often stout, 4 to 7 or even 12 cm. long; Flowers 14 cm. long, outer perianth-segments white but tinged with red or brown; inner perianth-segments white, acuminate; style green below, cream-colored above; stigma-lobes cream-colored, about 18, 1.5 cm.

long; fruit globular.

Plant low, 1 meter high or more, or sometimes prostrate and forming dense thickets; branches 7 to 8 cm. in diameter, with 12 or 13 ribs; areoles large, circular, filled with short wool; spines about 20. Very formidable, often 7 to 8 cm. long; central spines several, 2 to 6 cm, long; flowers large, white, about 10 cm long: inner perianth-segments acute; scales of ovary and tube subtending black hairs,

At first columnar, in age becoming much branched, 10 to 12 meters high; trunk woody, up to 4·5 cm. in diameter; branches 1 to 2 dm. in diameter; ribs 8 to 14, prominent, 2 to 4 cm. high, obtuse; areoles large, 1 to 1.5 cm. in diameter, felted, 2 to 3 cm· apart; spines 8 to 15, subulate, yellow, up to 8 cm. long; flowers very large, 15 to 20 cm. long, 12.5 cm. broad; inner perianth-segments oblong, 7 cm. long, acute, white ;scales on the ovary and Flower-tube ovate, mucronate-tipped, their axils filled with long brown wool.

This is a very large cactus, called in Argentina cardon grande. It has frequently been confused with another species, T, pasacana, of the same region, but it is more branched, with fewer ribs, different spines, and large flowers.

Growing in large clusters made up of many slender, erect or ascending branches, 2 to 4 meters high; ribs about 16, low, rounded, separated by narrow intervals; areoles filled with tawny felt, closely set, large; spines numerous, at hrst yellowish to brown; radial spines acicular, often only 1 cm. long or less; central spines much stouter and often 4 cm. long; flowers 1 from an areole, 8 to 11 cm. long, slender, somewhat curved near the base; ovary and Flower-tube bearing small ovate scales, their axils filled with long white and brown hairs; outer perianth-segments narrow, acute, passing into broader ones, simply mucronate, pinkish; Inner perianth segments thinner and a little broader than the outer ones, obtuse, 1.5 cm. long, greenish to brownish (not white) ; filaments numerous, slender, scattered over the narrow throat, somewhat exserted: style bulbose at base, slender, 7 cm. long, exserted; stigma-lobes short, greenish ;lower part of tube proper 1.5 cm. long, somewhat scabrous within; fruit Globular, 3 to 4 cm. in diameter, yellowish to reddish, splitting open on one side and exposing the pulp;seeds black, shining, 2 mm. long, a little longer than broad, minutely punctuate.

More or less cespitose, forming clumps 8 to 20 dm. broad; stems 8 to 16 dm. high, cylindrical, 4 to 5 cm in diameter; ribs 12 to 18, low, rounded; areole approximate, often only 5 to 7 mm. apart; spines numerous, acicular, unequal, the longest often 5 to 6 cm. long, yellowish to brown; flowers very variable in color and size, red to yellow, 7 to 10 cm. long, broadly funnel form ; scales on the ovary bearing long brown hairs.

Cespitose, forming large clumps often 1 to 3 meters in diameter: joints erect or spreading, 6 dm. Long or less, 14 cm. in diameter or less, rounded at apex; ribs 9 to 11, low, rounded or obtuse; areoles large, white-felted when young, 2 to 3 cm. apart; spines subulate, brownish yellow, more or less mottled; radial spines to or more, more or less spreading, unequal, the longest 4 cm, long; central spines several, the longest nearly 10 cm. long; Flowers very large, funnel form , very fragrant, showy, 15 cm. long; scales on flower tube ovate, acuminate, bearing long hairs in their axils; inner perianth-segments white, oblong; fruit globose to ellipsoid, splitting on one side.

Cespitose, forming clumps 2 to 10 dm. in diameter , the branches usually simple, erect, or ascending, sometimes 6 dm. high, 5 to 6 cm. in diameter, very spiny; ribs 15 to 18, very low, 4 to 5 mm. high, obtuse; areoles circular, rather large, approximate, 4 to 8 mm. apart, densely white-felted when young: spines numerous, very variable as to color and length, either white, yellowish, or pinkish to nearly black, 1 to 5 cm .long, acicular; Flowers white, large, 20 cm. long, funnel form, the scales on the ovary and tube with long silky hairs in their axils; seeds black, glossy, about 2 mm. long; hilum basal but oblique.

Cespitose, cylindrical, 3 to 5 dm. high, 10 to 12.5 cm. In diameter, light green; ribs about 14, 10 to 15 mm. high: areoles approximate, 5 to 7 mm. apart, white-felted when young; spines about 10, acicular, 12 mm. long or less, light yellow; Flowers from the top of plant, 15 to 18 cm. Long ;tube slender; outer perianth segments linear; inner segments probably white; scales of the ovary and flower-tube bearing long brown hairs.

Plants simple or cespitose, slender, 15 to 25 cm. high, 6 cm, in diameter, dark green, shiny; ribs 14 to 18, low, 5 mm. high, somewhat crenate; spines yellowish, flexible, 5 to 10 mm. long; radial spines at first 9. in age more numerous; central spines 2 to 8; Flower-bud pointed, covered with black wool ;Flowers funnel form , several from the top of the plant, inodorous, 20 to 22 cm. long; scales on the ovary and flower-tube with hairy axils; inner perianth-segments acute, oblong, white; fruit edible, agreeable.

 Definitions are provided by the New Shorter Oxford English Dictionary.

 To use this key make the most appropriate choice from the presented choices.

At two points you will have to make a choice regarding the flowers. If you have yet to see flowers on your plant please keep following point. In mind

The first choice is "limb of flower broad or narrow". By far Limb of flower broad is the most likely choice but if this leads to a choice. where. The entry doesn't seem to correspond to the observable characteristic of your specimen then check entries 14 and 15

 The second choice requires form and color of flower. There is no most likely option. But this is used to distinguish between a small number of plants

Acknowledgment

Version:1

The information presented in this document is mainly from The Cactaceae. Some entries are difficult to read but this is the way they are in the book. I have included a glossary to help understand some of the entries. The key to identification presented the Cactaceae has been changed into a more intuitive format but the information has not been changed.

This document was created by Ramon Rodrigo. It can be freely distributed without modification but not sold for profit (unless you cut me in on the profit )

I have plans of further updating this document as Baker and Rose have not included Trichocereus scoplocolis in their list or key to identification but shall canvass a range of people as to where and how it should be inserted and identified.