Origin and Habitat: Thelocactus bicolorSN|15121]]SN|3420]] has a very large range in the northern Chihuahuan desert in USA (Texas) and Mexico(Chihuahua, Coahuila, Durango, Nuevo León, San Luis Potosí, Tamaulipas, Zacatecas).
Altitude: 800-2200 metres above sea level.
Habitat: Occurring in mattoral xerofilo together with Larrea tridentata, Fouquieria splendensSN|15717]]SN|15717]], Jatropha spathulata, Agave lechuguillaSN|23013]]SN|23013]] and Yucca thompsonianaSN|27876]]SN|27876]] on flat gravelly soils, limestone or sandstone slopes of hills or outcrops and alluvial fans in desert or grassland. (The extensive distribution range of this species has led to the formation of many local forms which in the years have been formally named. Most of these names are not accepted by many botanists that treat them as synonyms, but they still have a value for a collector because they identify plants with particular characters). It is abundant, and there are no major threats to this species. In the same area it is possible to find several cactus species like: Echinocactus horizonthaloniusSN|1711]]SN|1711]], Homalocephala texensisSN|2230]]SN|2230]], Coryphantha echinus, Coryphantha runyoniiSN|10249]]SN|10025]], Coryphantha validaSN|10025]]SN|10249]], Coryphantha scherii, Mammillaria pottsiiSN|25133]]SN|9355]], Mammillaria formosaSN|15974]]SN|15832]], Mammillaria grusoniiSN|15832]]SN|15974]], Mammillaria chicaSN|9355]]SN|25133]], Echinocereus pectinatusSN|7932]]SN|8503]], Echinocereus stramineusSN|7820]]SN|7817]], Echinocereus conglomeratusSN|7817]]SN|7820]], Echinocereus merkeriSN|8503]]SN|7932]], Thelocactus conothelosSN|3420]]SN|15121]] v. argenteus, Gladulicactus uncinatus, Grusonia bradtianaSN|7500]]SN|7500]], Opuntia imbricataSN|8157]]SN|8157]], Epithelantha micromerisSN|6936]]SN|6936]] v. gregii, Gymnocactus beguiniiSN|1913]]SN|1913]], Echinomastus unguispinusSN|14901]]SN|14901]], Lophophora williamsiiSN|1117]]SN|1117]], Escobaria duncaniiSN|10200]]SN|10200]], Leuchtenbergia principisSN|12924]]SN|12924]], Astrophytum senileSN|3591]]SN|3591]], Hamatocactus hamatacanthus and Neolloydia conoideaSN|10089]]SN|10089]].

• Thelocactus bicolor (Galeotti ex Pfeiff.) Britton & Rose
• Cactus bicolor Teran & Berland.
• Echinocactus bicolor Pfeiff. in Pfeiff. ex Pfeiff.
• Echinocactus rhodophthalmus Hook.
• Echinocactus rhodophthalmus var. ellipticus Hook.
• Ferocactus bicolor (Galeotti ex Pfeiff.) N.P.Taylor
• Hamatocactus bicolor I.M.Johnst.
• Thelomastus bicolor (Galeotti ex Pfeiff.) Frič in Kreuz.

• Thelocactus bicolor (Galeotti ex Pfeiff.) Britton & Rose
• Cactus bicolor Teran & Berland.
• Echinocactus bicolor Pfeiff. in Pfeiff. ex Pfeiff.
• Echinocactus rhodophthalmus Hook.
• Echinocactus rhodophthalmus var. ellipticus Hook.
• Ferocactus bicolor (Galeotti ex Pfeiff.) N.P.Taylor
• Hamatocactus bicolor I.M.Johnst.
• Thelomastus bicolor (Galeotti ex Pfeiff.) Frič in Kreuz.
• Thelocactus bicolor var. commodus R.Haas
• Thelocactus bicolor subs. commodus (R.Haas) Doweld
• Thelocactus bicolor var. schottii (Engelm.) Krainz in Krainz
• Echinocactus bicolor var. schottii Engelm.
• Echinocactus schottii Small
• Thelocactus schottii (Engelm.) Kladiwa & Fittkau
• Thelocactus bicolor subs. swobodae Halda & Horáček
• Thelocactus bicolor var. texensis Backeb.
• Thelocactus bicolor var. tricolor (K.Schum.) F.M.Knuth in Backeb. & F.M.Knuth
• Echinocactus bicolor var. tricolor K.Schum.
• Echinocactus bicolor f. tricolor (K.Schum.) Schelle
• Thelocactus bicolor subs. zwakii Chvastek & Halda

• Thelocactus bicolor subs. bolaensis (C.Runge) Doweld
• Echinocactus bicolor var. bolaensis (C.Runge) K.Schum.
• Echinocactus bicolor f. bolaensis (C.Runge) Schelle
• Echinocactus bolaensis C.Runge
• Ferocactus bicolor var. bolaensis (C.Runge) N.P.Taylor
• Thelocactus bicolor var. bolaensis (C.Runge) A.Berger
• Thelocactus bicolor var. bolansis (K.Schum.) F.M.Knuth
• Thelocactus bolansis hort.
• Thelomastus bicolor bolansis (C.Runge) Frič in Kreuz.
• Thelocactus bicolor var. wagnerianus (A.Berger) Krainz in Krainz
• Echinocactus wagnerianus var. A.Berger A.Berger
• Thelocactus wagnerianus A.Berger
• Thelomastus bicolor wagnerianus (A.Berger) Frič in Kreuz.

• Thelocactus bicolor subs. flavidispinus (Backeb.) N.P.Taylor
• Ferocactus bicolor var. flavidispinus (Backeb.) N.P.Taylor
• Thelocactus bicolor var. flavidispinus Backeb.
• Thelocactus flavidispinus Backeb.

• Thelocactus bicolor subs. heterochromus (F.A.C.Weber) Mosco & Zanov.
• Echinocactus heterochromus F.A.C.Weber
• Ferocactus heterochromus N.P.Taylor
• Thelocactus heterochromus (F.A.C.Weber) Oosten
• Thelomastus heterochromus (F.A.C.Weber) Frič in Kreuz.
• Thelocactus bicolor var. pottsii (Schur ex Salm-Dyck) Backeb.
• Echinocactus bicolor var. pottsii Schur ex Salm-Dyck
• Echinocactus bicolor f. pottsii (Schur ex Salm-Dyck) Voss in Vilm.
• Echinocactus pottsii Schur ex Salm-Dyck
• Thelocactus pottsii (Schur ex Salm-Dyck) Britton & Rose
• Thelocactus heterochromus longispinus

• Thelocactus bicolor subs. schwarzii (Backeb.) N.P.Taylor
• Ferocactus bicolor var. schwarzii (Backeb.) N.P.Taylor
• Thelocactus bicolor var. schwarzii (Backeb.) E.F.Anderson
• Thelocactus schwarzii Backeb.

• Thelocactus bicolor cv. albiflorus
• Thelocactus bicolor cv. inermis

Description: Globular usually solitary cacti up to 10 cm in diameter.
Stem: Ovoidal, 8-20 cm tall, 5-12 cm wide.
Ribs: 8, distinct.
Tubercles: Rounded.
Areoles: With glands.
Central spines: 3-4, 15-75 mm long, ochre to reddish, straight, acicular or slightly bent inwards.
Radial spines: 8-18, 10-30 mm long, ochre to reddish, straight, acicular.
Flowers: 55-110 mm wide, magenta with a red throat from early spring to autumn.
Remarks: This Taxon has lots of synonyms ( like many other cacti) whit several controversial varieties and subspecies and comprises a multitude of different forms, but where each form is linked to others by populations of plants with intermediate characteristics. Five subspecies are recognized, the nominate form, subsp. bolaensis (Runge) Doweld, subsp.,flavidispinus (Backeb.) N.P.Taylor, subsp. heterochromus (F.A.C.Weber) Mosco & Zanov. and subsp. schwarzii (Backeb.) N.P.Taylor.

Bibliography: Major references and further lectures
1) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
2) Goettsch, B.K., Heil, K., Terry, M. & Corral-Díaz, R. 2013. Thelocactus bicolor. In: IUCN 2013. "IUCN Red List of Threatened Species." Version 2013.2. <www.iucnredlist.org>. Downloaded on 11 January 2014.
3) James Cullen, Sabina G. Knees, H. Suzanne Cubey "The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass" Cambridge University Press, 11/Aug/2011
4) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006
5) Nathaniel Lord Britton, Joseph Nelson Rose “Cactaceae: Descriptions and Illustrations of Plants of the Cactus Family” Courier Dover Publications, 1963
6) Del Weniger “Cacti of the Southwest: Texas, New Mexico, Oklahoma, Arkansas, and Louisiana” University of Texas Press, 1969

Cultivation and Propagation: Thelocactus bicolorSN|3420]]SN|3420]] is a summer grower species easy to cultivate, more cold tolerant than most and less fussy regarding soil conditions.
Growth rate: It is a relatively rapidly growing and easily flowering species that will make clumps given the best conditions.
Soils: It likes very porous standard cactus mix soil, but can become too elongated if compost is too rich.
Repotting: Use pot with good drainage.
Watering: Water regularly from Spring to Autumn, but do not overwater(Rot prone), keep dry in winter.
Fertilization: Feed with a high potassium fertilizer in summer.
Hardiness: Reputedly somewhat resistant to frost if kept on the dry side prior to, and during, cold weather (hardy to -7 C ° C, or less for short periods).
Exposition: Requires full sun or light shade and careful watering to keep plant compact with strong coloured spines. Tends to bronze in strong light, which encourages flowering and heavy spine production.
Uses: It is an excellent plant for container growing. It always looks good and stays small. It look fine in a cold greenhouse and frame or outdoor in a rockery.
Pests & diseases: It may be attractive to a variety of insects, but plants in good condition should be nearly pest-free, particularly if they are grown in a mineral potting-mix, with good exposure and ventilation. Nonetheless, there are several pests to watch for:
- Red spiders: Red spiders may be effectively rubbed up by watering the infested plants from above.
- Mealy bugs: Mealy bugs occasionally develop aerial into the new growth among the wool with disfiguring results, but the worst types develop underground on the roots and are invisible except by their effects.
- Sciara Flies: Sciara flies are one of the major problems for seedlings. It is a good practice to mulch your seedlings with a layer of grit, which will strongly discourage the flies.
- Scales: Scales are rarely a problem.
It is wise to treat your whole collection with a systemic insecticide twice a year in spring and autumn.
- Rot: Rot is only a minor problem with cacti if the plants are watered and “aired” correctly. If they are not, fungicides won't help all that much.
Propagation: From seed, since the plant rarely produces plantlets.. Seeds germinate in 7-14 days at 21-27° C in spring, remove gradually the glass cover as soon the plants will be well rooted (ca 1-2 weeks) and keep ventilated, no full sun for young plants!