| 1 | Leaves | polystichous or spiralling, not distichous | 2 |
| | distichous | 17 |
| 2 | Plant | sterile, without inflorescence, stemmed, with 1 -1.5 mm wide leaves, from coast of northern Chile to south Peru | landbeckii |
| | not sterile, always with inflorescence | 3 |
| 3 | Flower bracts | glabrous, seldom with wholely few and hardly visible scales | 4 |
| | wholely or at least in the upper part clearly scaled | 10 |
| 4 | Flower bracts | "with few, hardly visible scales, 6 - 9-nerved, widest at the base; Sepals uniformly short connate (or the posterior pair somewhat higher), narrow triangular, blunt, 5-nerved; Petal dirty yellow; Leaf stiff erect, with clearly large nerves" | erecta |
| | "and sepals totally glabrous; Petals brown to coffee brown; Leaves edged, one clearly large nerve" | 5 |
| 5 | Plant | "stemless or short stemmed; Leaves 15 - 45 mm long, spreading, not densely imbricate " | 6 |
| | clearly stemmed, Leaves under 15 mm long, densely imbricate | 7 |
| 6 | Flower bracts | "mostly as long as the sepals; Plant robust; Leaves 20 - 45 nm long, at the base 3-5 mm wide" | funebris |
| | "mostly half as long as the sepals; Plant slender, Leaves mostly under 20 mm long, 2-3 mm wide at base, ± sharply acuminate; very seldom with distichous leaves" | rectangula |
| 7 | Flower bracts | "5- 6-nerved; Inflorescense almost always at anthesis clearly stemmed; sepals (4-) 5-nerved" | 9 |
| | "1 (-3)- nerved, mostly glabrous; Inflorescense at anthesis almost always not stemmed" | 8 |
| 8 | Peduncle | "at fruiting mostly longer; sepals 3 (-5)-nerved, glabrous, with a mid nerve continuously to the tip; petals violet. Plant diam 4-7 mm " | pedicellata |
| | "at fruiting not longer, sepals 5-6-nerved, 1/3 to 2/3 or the edges scaled; petals yellow; Plant in diam 3-5 mm" | minutiflora |
| 9 | Flower bracts | "oval; sepals at widest or above the middle, 5.6 – 6.5 mm long; petals yellowish or brownish. " | aizoides |
| | "narrow triangular; sepals at the widest below the middle, sometimes scaled, 8.5 mm long; petals violet" | aff. Aizoides (possibly a form of T. brealitoensis ) |
| 10 | Flowers | small, flower bracts (4-) 6-7 (-10) mm long, sepals 6-7 mm long. Inflorescense few flowered, seldom l-flowered, peduncle mostly present | 11 |
| | large, Flower bracts (8.5- ) 10 - 18 mm long, sepals (8-) 9-14 mm long, Inflorescense mostly 1-2-flowered, seldom to 4-flowered, peduncle present or missing | 13 |
| 11 | Plant | stemless or at least short stemmed | 12 |
| | "clearly stemmed; peduncle mostly distinct, seldom missing. Leaves thin, tipped, appressed (""trlcholepis"" ) or spreading. (""polytrichoides ""), to 15 mm long; petals yellow; Rhachis not geniculate" | tricholepis var tricholepis |
| 12 | Leaves | "strong, quite thick; Rhachis mostly geniculate; Petals yellow to orange yellow " | loliacea |
| | "thin, very slender, not thick, 20-50 mm long; Rhachis not geniculate; Petals brown, seldom yellow" | tricholepis var macrophylla |
| 13 | Leaves | "to 15 mm long, densely imbricate; Plant 4-10 cm long, compact, stemmed" | 14 |
| | "20 - 60 mm long, not densely imbricate; plant not compact, ± stemmed" | 15 |
| 14 | Inflorescence | "sessile; Flower bracts 9-nerved, 12 mm long; Sepals 11 mm long; Petals 7-nerved brown yellow; Leaves spreading and bent outwards. Plant very short stemmed" | angulosa |
| | "clearly stemmed; flower bracts 11-12-nerved, 8.5 – 10.5 mm long; Sepals 8-9 mm long, Petals 5-7-nerved, violet; Leaves straight, erect. Plant clearly stemmed." | brealitoensis |
| 15 | Leaves | "3-5 mm wide; Plant strong; epiphytc (seldom epilithic) in south Peru (Arequipa), Bolivia and Argentinia" | 16 |
| | "1–1.5 mm wide; Plant erect delicate; terrestrial in sand or epiphytic in south Peru (Coast) und North Chile" | landbeckii |
| 16 | Leaves | "wide at base, edges not fused appressed scaled, 30-50 mm long; Flower bracts 15-17-nerved; Sepals in the upper 40-70 % large scaled; Petals dark violet" | gilliesii subsp polysticha |
| | "at base hardly wider that the middle, edges joined, ± erect scaled, 20-40 mm long; flower bracts 12-13-nerved; Sepals in the upper 50-65% large scaled; Petals yellowish" | hirta ( seldom polystichous Form) |
| 17 | Plant | "with longer thin internodes, hanging, to 8 m long; Sepals glabrous or almost glabrous; Petals green, seldom yellow ( in Peru and Ecuador)" | usneoides |
| | "with compact stem, not with longer thin internodes, sometimes almost stemless, not over 30 cm long; Petal never clear green, at the most brown green" | 18 (mollis) |
| 18 | Leaves | "± soft, 1.5-3 mm Ø, round or almost round,, without a distinct pungent tip; Flower mostly relatively small, Sepals 4.5 -9(10.6) mm long; Plant mostly relatively slender (Exceptions: caliginosa, hirta and cotagaitensis Sepals 8-14 mm long; also steps 19-22)" | 19 |
| | "hard, often with clearly visible light Sclerenchyma, with pungent tip, 3-6 mm Ø; Flowers relatively large, Sepals (8-) 9-14 mm long (compare with step 19); Plant strong, 5-30 cm long" | 28 |
| 19 | Plant | "strong and mid size to large, Leaves 2-4 mm Ø, round or upper side concave, 4-14 cm long, mostly with ± blunt tip; Flower relatively large, Sepals 8-14 mm long, mostly distinct scaled" | 20 |
| | "small to mid size, slender erect, Leaves 1-3 mm Ø, 0.5-10 cm long; Flowers relatively small, Sepals 4.5-9 mm long, abundantly glabrous" | 23 |
| 20 | Plant | "large, 15 - 25 cm long, short stemmed, Leaves often with glabrous sheath (seldom scaled) , upper side somewhat concave, to 14 cm long, a little bent; Flowers scented" | 21 |
| | "clearly stemmed, much smaller, 5-15 cm long; Leaves 2-4 cm long; Inflorescense with relatively short stem, peduncle 1-2 mm Ø, 1-3(-4) cm long" | 22 |
| 21 | Inflorescence | "10-15 cm long stem, 2-5-flowered; Petals yellow to yellow brown, seldom coffee-brown; Central Bolivian (Cochabamba) to south Argentina (Tucuman, La Rioja)" | caliginosa |
| | "to somewhat 3 cm stemmed; Petals coffee-brown; mid Argentina (Catamarca, La Rioja, Buenos Aires ) " | “myosura var saxicola” ( = gilliesii “var saxicola” nom prov. ) |
| 22 | Sepals | "similarly short connate, dense scaled; Plant clearly with erect scales" | irta |
| | "posterior much higher connate (53-64%), sparingly scaled to almost glabrous; Plant a little erect scaled" | cotagaitensis |
| 23 | Peduncle bracts | Below the flower of the inflorescense with 1-2 peduncle bracts directly under the flower bract | 24 |
| | No peduncle bracts directly under the flower bract | 27 |
| 24 | Sepals | "glabrous; Plant ± stemless" | 25 |
| | "± clearly scaled; Plant clearly and to 26 cm stemmed" | 26 |
| 25 | Leaves | "slender (particularly in south Brazil and Paraguay), 0.5-1.5 mm Ø, 4-10 cm long; Sepals lanceolate to oval-lanceolate, ± tipped, (5.8-) 7.5-8.4 ( -9.6) mm long , (2.6-) 3-3.5 (-3.8) mm wide; Petals blue, seldom white; south USA to Argentina and Uruguay" | recurvata (polymorphous and not well organised! ) |
| | "strong, 1.5-2 mm Ø; Sepals obovate, tip rounded, (8-) 9-10.6 mm long, (4.2-) 4.8-5.5 mm wide; Petals dirty brown; Andes of south Peru (Dept . Ayacucho, Dept. Cuzco ) " | aff. recurvata |
| 26 | Plant | "slender erect, Leaves thin and long; Inflorescense long stemmed, Chile and south Peru (? ) Coast" | landbeckii |
| | "strong erect, Leaves (2-) 3 mm Ø, dense white felt; Inflorescense sessile; south Bolivia (Dept. Tarija)" | mollis |
| | creeping habit flowers brown-reddish | mollis var reptans |
| 27 | Sepals | "wide lanceolate, mostly rounded at the tip, seldom acuminate or tipped, all ± clearly together connate, posterior a little higher connate than the anterior; flower bracts almost always glabrous" | capillaris s.l. (very polymorphous and not well organised! ) |
| | "almost long and seemingly slender, side nerves clearly short, anterior Sepal almost free, posterior very high (to 80%) connate;flower bracts mostly wholely or in the upper third scaled, seldom glabrous (williamsii)" | virescens s.l. (very polymorphous and not well organised!) |
| 28 | Flower | "cleistogamous, Sepals wide ovate-lanceolate, blunt to rounded, almost free or the posterior wholely a little connate, 7-9-nerved, 7.5-8.5 (-9) mm long, glabrous; Flower bracts glabrous (seldom with hardly visible few scales); Inflorescense mostly 2-flowered. Leaves hard, stiff, striped nerved, pungent" | castellanii |
| | "not cleistogamous ( T. hirta sometimes cleistogamous, however not obligatory); Bracts always scaled; Sepals 10-14 mm long" | 29 |
| 29 | Leaves | very hard, with striking Sclerenchyma, Plant middle size, seldom large | 30 |
| | without or with hardly visible sclerenchyma. | 31 |
| 30 | Plant | "stemless or short stemmed, Leaf sheath glabrous; Inflorescense sessile or very short stemmed; Sepals glabrous, equally almost free" | retorta |
| | "clearly stemmed, Leaf sheath scaled; Inflorescense stemmed; Sepals scaled, posterior connate to the middle" | andicola |
| 31 | Leaf | in cross-section round, not drawn together on the side | 32 |
| | drawn together on the side, very dense, 2-4 cm long, 4-5 mm thick, appressed scaled. Peduncle mostly missing, seldom to 5 (-10) cm long. Mid Argentina | gilliesii subsp gilliesii |
| 32 | Plant | "clearly stemmed; Leaves ± soft to moderately hard, mostly erect scaled" | 33 |
| | "± stemless, at the most short stemmed; Leaves hard or soft, mostly ± appressed scaled" | 34 |
| 33 | Posterior sepals | "more than half in length connate; Sepals glabrous or almost glabrous; Petals brown to dark violet" | cotagaitensis |
| | "seldom and very little connate; Sepals 1/3 to 2/3 scaled; Petals yellow or yellowish" | irta |
| 34 | Leaves | "hard, grey-green, crooked, at the tip but again bent forwards, 4-5 mm Ø, to 10 cm long; Sepals equally free" | myosura |
| | "relatively soft, arched, 2.5-3.5 mm Ø, to 15 cm long, mostly light green; posterior sepals to a ¼ connate, mostly however less" | mandonii |
(Key to Tillandsia sub genus Diaphoranthema by Till 1984)