Origin and Habitat: Southwestern USA (New Mexico, Arizona, Utah, west Texas and Colorado), Mexico (Sonora, Coahuila, Chihuahua)
Typical Locality: Texas, granitic region of the Llano. Lindheimer, 1847 (MO).

• Echinocereus roemeri Engelm. ex F.Haage
• Cereus roemeri Engelm.

• Echinocereus coccineus Engelm. in Wisliz.
• Cereus coccineus (Engelm.) Engelm.
• Echinocereus triglochidiatus var. coccineus (Engelm.) W.T.Marshall & T.M.Bock
• Echinocereus arizonicus subs. matudae (Bravo) Rutow
• Echinocereus matudae Bravo
• Echinocereus arizonicus subs. nigrihorridispinus W.Blum & Rutow in W.Blum et al.
• Echinocereus canyonensis Clover & Jotter
• Echinocereus coccineus subs. aggregatus (Engelm. ex S.Watson) W.Blum, Mich.Lange & Rutow
• Cereus aggregatus (Engelm. ex Emory) J.M.Coult.
• Coryphantha aggregata (Engelm. ex Emory) Britton & Rose
• Coryphantha neovivipara var. aggregata (Engelm. ex Emory) Y.Itô
• Coryphantha vivipara var. aggregata (Engelm. ex Emory) W.T.Marshall
• Echinocereus aggregatus (Engelm. ex Emory) Rydb.
• Escobaria aggregata (Engelm. ex Emory) Buxb.
• Mammillaria aggregata Engelm. in Emory
• Mammillaria vivipara var. aggregata (Engelm. ex Emory) L.D.Benson
• Echinocereus coccineus var. arizonicus (Rose ex Orcutt) D.J.Ferguson
• Echinocereus arizonicus Rose in Orcutt ex Orcutt
• Echinocereus triglochidiatus var. arizonicus (Rose ex Orcutt) L.D.Benson in L.D.Benson
• Echinocereus coccineus var. gurneyi (L.D.Benson) S.Brack & K.D.Heil
• Echinocereus triglochidiatus var. gurneyi L.D.Benson
• Echinocereus coccineus var. kunzei (Gürke) Backeb.
• Echinocereus kunzei Gürke
• Echinocereus coccineus var. rosei (Wooton & Standl.) A.D.Zimmerman
• Echinocereus rosei Wooton & Standl.
• Echinocereus triglochidiatus var. rosei (Wooton & Standl.) W.T.Marshall
• Echinocereus decumbens Clover & Jotter
• Echinocereus engelmannii subs. decumbens (Clover & Jotter) W.Blum & Mich.Lange in W.Blum et al.
• Echinocereus engelmannii var. decumbens (Clover & Jotter) L.D.Benson
• Echinocereus hexaedrus (Engelm.) Rümpler
• Cereus hexaedrus Engelm. & J.M.Bigelow
• Echinocereus paucispinus var. hexaedrus (Engelm. & J.M.Bigelow) K.Schum.
• Echinocereus triglochidiatus var. hexaedrus (Engelm.) Boissev. in Boissev. & C.Davidson
• Echinocereus krausei De Smet. in Förster
• Echinocereus neomexicanus Standl.
• Cereus neomexicanus (Standl.) Tidestr. in Tidestr. & Kittell
• Echinocereus triglochidiatus var. neomexicanus (Standl.) W.T.Marshall
• Echinocereus phoeniceus (Engelm.) Rümpler
• Cereus phoeniceus Engelm.
• Echinocereus phoeniceus var. albispinus Rümpler in Förster
• Echinocereus phoeniceus var. longispinus Rümpler in Förster
• Echinocereus phoeniceus var. rufispinus Rümpler in Förster
• Echinocereus roemeri Engelm. ex F.Haage
• Cereus roemeri Engelm.
• Echinocereus toroweapensis (P.C.Fisch.) H.Fürsch
• Echinocereus triglochidiatus var. toroweapensis P.C.Fisch.

• Echinocereus coccineus subs. paucispinus (Engelm.) W.Blum, Mich.Lange & Rutow in W.Blum et al.
• Cereus paucispinus Engelm.
• Echinocereus coccineus var. paucispinus (Engelm.) D.J.Ferguson
• Echinocereus paucispinus (Engelm.) Rümpler
• Echinocereus triglochidiatus var. paucispinus (Engelm.) W.T.Marshall & T.M.Bock

Description: Echinocereus roemeri is a densely caespitose cactus specie, often growing in large colonies up to 1 m in diameter, containing sometimes 200 or more simple stems. Echinocereus roemeri is a cactus with both hermaphroditic (bisexual) and dioecious (male and female) forms of flowers on different plants. Male flower shows pollen-filled anthers surrounding the base of the stigma lobes, while functional female flowers from different plants show reduced filaments and empty anther sacs held below the stigma lobes.
Stems:Dark green, ovoid to cylindrical, 20-40 cm tall, 3 to 5 in diameter .
Ribs: 8 to 11 somewhat tuberculed.
Spines: Acicular, mostly undifferentiated between radials and centrals;
Radial spines: (5-)8-12(-20) round in cross-section, 1-2 cm long, usually whitish.
Central spines: 0 to 4, longer and stouter somewhat angular in cross-section, the main one often flattened, up to 7.5 cm long; usually yellowish or whitish, but sometimes reddish or blackish.
Flowers: Borne below the stems apex, oftem unisexual (plants dioecious) broad Infundibuliform, orange-red, crimson or (rarely) pinkish, 3-10 cm long, up to 8 cm in diameter, perianth-segment obtuse or retuse, stigma with 7 or 8 lobes, usually greenish, areoles on flower, and ovary felted, bearing short white bristly spines.
Blooming season: Spring. The blooming period of large plants can extend over a period of weeks, with each bloom remaining open for several days and nights. The flowers appear specialized for hummingbirds, but are also pollinated by bees. They are huge and highly rewarding, and daily nectar production averaged 30 mg sugar/flower. This set of traits represents a syndrome rare among hummingbird flowers, in which the flower fits the head rather than just the bill, and birds are well rewarded for a risky or inconvenient visit.
Fruits: Globose, becoming red, with spines falling away.

Notes: Nowadays E. roemeri is regarded by botanists as Echinocereus coccineusSN|10576]]SN|7140]] (ssp. coccineus). This taxon is closely related to and easily confused with Echinocereus triglochidiatusSN|7140]]SN|10576]], and there are many cases of hybridization between the species.

Cultivation and Propagation: Echinocereus roemeri is fairly easy to grow. It makes great potted specimens.
Soil: Use a mineral well permeable soil with little organic matter (peat, humus). It grows in limestone areas of Texas (Big Bend area) and adjacent areas of Mexico, so will probably benefit from extra calcium in its soil.
Growth rate: It grows well, though slowly, but it possible to increase the speed of growth to some extent by providing adequate amount of water, warmth, and a liquid fertilizer diluted half strength during the active growing season, but it’s susceptible to rotting if too wet. Most plants will offset readily, and clumps can be produced in a few years.
Soil: It needs a very porous, slightly acidic potting medium (add pumice, vulcanite, and perlite). Outdoors it does well on poor, rocky soils.
Exposure: It likes a sunny position also blasting sun in summer. If grown indoor provide 4 to 6 hours, or more, direct morning or afternoon sun.
Watering: It is sensitive to overwatering (rot prone) needs a very good drainage to avoid rotting, but requires more moisture than true desert cacti to grow and produce flowers.
Hardiness: It its natural environment it is very cold resistant from -10° to -25° C (depending on clones) or less for short periods of time. It can be grown outdoors in Mediterranean warm-temperate climates, But for safe cultivations needs anyway to kept above 5 °C and dry in winter. But it can tolerate temperatures down to -5° C (or even less) for very short periods if very dry and ventilated. During winter month, put them in a cool luminous place and encourage them to enter winter dormancy by withholding water and fertiliser over the winter as they will etiolate, or become thin, due to lower levels of light.
Maintenance: Repot every two years. Needs lots and lots of space to grow, use large shallow container or bowl filled with very porous compost. It like pots with generous drain holes.
Pest & diseases: They are susceptible to fungal diseases if overwatered, but are not nearly as sensitive as many other cacti, especially in warm weather. If kept damp through cold periods, they will invariably suffer.
Garden uses: It is a fine plant for a rock garden or container, contrasts well with agaves, yuccas, and low-growing flowering plants.
Grafting stock: The taller fast-growing forms o Echinocactus coccineus and of Echinocactus triglochidiatus are highly recommended stocks for grafting cold hardy type cactus species. These can be used as cold hardy type stocks for almost all types of cactus, while still retaining the original natural grown look to the scion.
Food: The Native Americans of New Mexico ate the fruit fresh or preserved.
Traditional Medicine: This species is used medicinally as a heart stimulant.
Propagation: Cutting as it branches freely from the base; Also can be grown from seeds. The seeds may be germinated and grown in containers. Their main requirements consist of high humidity levels, free-draining soil mix, and enough water, light, and nutrition.