Accepted Scientific Name: Thelocactus bicolor (Galeotti ex Pfeiff.) Britton & Rose
Bull. Torrey Bot. Club 49: 251. 1922
Thelomastus bicolor (Thelocactus bicolor) Photo by: Peiffer Clement
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]].
Synonyms:
See all synonyms of Thelocactus bicolor
Common Names include:
ENGLISH: Glory of Texas, Texas Pride, Straw Spine Cactus
SPANISH (Español): Biznaga pezón bicolor
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.
Subspecies, varieties, forms and cultivars of plants belonging to the Thelocactus bicolor group
- Thelocactus bicolor (Galeotti ex Pfeiff.) Britton & Rose: (subsp. bicolor) has extremely variable spination, 1-4 central spines, 8-15 radials, and usually bicolored flowers; Distribution: Chihuahuan Desert of Texas and Mexico and in the Tamaulipan thorn shrub vegetation along the Rio Grande.
- Thelocactus bicolor subs. bolaensis (C.Runge) Doweld: has dense, strong, and white spination. Distribution: Sierra Bola in Coahuila
- Thelocactus bicolor var. commodus R.Haas: It has been described as having only one central spine, but there are 2 upper central spines so appressed to the stem that they can be easily mistaken for radials. Therefore it has three central spines and its maintenance at variety rank is not justified. Distribution: near Montemorelos, Tamaulipas, outside the limits of the Chihuahuan Desert.
- Thelocactus bicolor subs. flavidispinus (Backeb.) N.P.Taylor: has spines covering the entire plant, 3 central spines, 12-17 radials, and (usually) bicolored flowers; Distribution: Chihuahuan Desert vegetation in Texas and, possibly, neighboring Mexico.
- Thelocactus bicolor subs. heterochromus (F.A.C.Weber) Mosco & Zanov.: has stems with wider ribs and stouter, subulate, spines banded in red. Distribution: Coahuila and Durango (This is the westernmost taxon in the genus)
- Thelocactus bicolor var. pottsii (Schur ex Salm-Dyck) Backeb.: intermediate plants between heterochromus and bicolor, but definitely belong to heterochromus for their lack of areolar glands. Distribution: Chihuahua
- Thelocactus bicolor var. schottii (Engelm.) Krainz in Krainz: It is characterized by a very long, papery upper spine. Distribution: Big Bend area
- Thelocactus bicolor subs. schwarzii (Backeb.) N.P.Taylor: has no central spines (may however appear sporadically), 13-14 radials, and tricolored flowers. Distribution: Tamaulipas east of the Sierra Madre Oriental.
- Thelocactus bicolor subs. swobodae Halda & Horáček
- Thelocactus bicolor var. texensis Backeb.: Texensis is an invalid name published by Backeberg applying to a Texas form.
- Thelocactus bicolor var. tricolor (K.Schum.) F.M.Knuth in Backeb. & F.M.Knuth: it is a form with bright red spines. Distribution: Saltillo, Coahuila.
- Thelocactus bicolor var. wagnerianus (A.Berger) Krainz in Krainz: it is differentiated from Thelocactus bolaensis for its columnar stem, the reddish spines and the lack of flattened spines. Distribution: west of Saltillo, Coahuila
- Thelocactus bicolor subs. zwakii Chvastek & Halda: it has smaller stem and flowers . It is not sufficiently distinct to deserve a subspecies rank. Distribution: Castanos in Coahuila.
- Thelocactus bicolor cv. albiflorus: white flowering form. Garden origin.
- Thelocactus bicolor cv. inermis: Spineless cultivar with flamboyant jagged flowers.
- Thelocactus heterochromus longispinus
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
Thelomastus bicolor (Thelocactus bicolor) Photo by: Valentino Vallicelli Thelomastus bicolor (Thelocactus bicolor) Photo by: Carolina González Thelomastus bicolor (Thelocactus bicolor) Photo by: Valentino Vallicelli Thelomastus bicolor (Thelocactus bicolor) Photo by: Carolina González - it is Common in cultivation due to its ease of cultivation and the beautiful flowers freely produced. (Thelocactus bicolor) Photo by: Valentino Vallicelli Thelomastus bicolor (Thelocactus bicolor) Photo by: Carolina González Thelomastus bicolor (Thelocactus bicolor) Photo by: Carolina González An unusual Thelocactus bicolor with a very pale pink flower. (Thelocactus bicolor) Photo by: Colin Bundred 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!
Your Photos
by Valentino Vallicelli
by Valentino Vallicelli
by Carolina González