Ritter 1980, Kakteen in Südamerika (3):1087
 

Ritter provides the full German description and comments that C. mollicula is closely related. 

Differences are: larger and more offsetting, more and higher ribs, more pronounced areoles, spines more robust, radial spines more adpressed, flower larger and more brightly yellow, fruit larger with numerous and larger scales.  Discovered in 1956 FR523.

The species seems to be highly variable as some seeds of FR523 produced plants of C. rubriflora.

Although Ritter points at C. montana (now C. hypogeae var. montana) as C. grandiflora's closest ally, current thinking (Charles 1998) classifies C. grandiflora as a variety of C. cinerascens.

Taylor N. P. 1981, A commentary on Copiapoa , The Cactus and Succulent Journal of Great Britain, 43(2/3): 49-60

Taylor reports C. grandiflora and distinctive when compared to C. hypogaea and C. cinerascens.

Butcher summarises the above information and adds that Backeberg believed it to be related to C. montana (C. hypogeae var montana (Ritter) Charles) and that Karl Knize used the name grandiflora in error for KK 196 (should be C. malletiana).

KK 1067 is also in doubt as its habitat (Agua Verde) suggests a form of C. coquimbana.

Adriana Hoffmann records Copiapoa cinerascens (Salm-Dyck) Britton et Rose var grandiflora (Ritter) A. Hoffmann comb. nov.

Ritter 523: Copiapoa grandiflora F. Ritter - Taxon 12(1): 30, 1963. (First mentioned in Backeberg, Die Cact. 6: 3828, 1962 (as nom. nud.).)
Typus (T): Ritter 523 (U 145311B, SGO, ZSS [seeds only, status ?]) (Holotype cited for U l.c., 28.).

loc. 1:  Chile: ,,Esmeralda“.
SGO 124883 ISO - rad, corp. ar, sp
U 145311B HOLO - rad, corp. ar, sp ("Junges Exemplar, noch nicht sprossend“ = young plant, not yet producing offsets. Labelled as "Holotypus“ by Ritter, but without collection data.)
ZSS S10312 Type number - sem (Leg. F. Ritter 1957. No locality data associated with this specimen.)

loc. 2: Chile: ,,Esmeralda Nr. 2“. -/2. /1956.
ZSS SR13464 ISO-sem

The authors do not wish to be involved in taxonomic discussion and refer to the plant by its basionym.  They report plants resembling C. grandiflora in the Pan de Azucar, growing with C. cinerascens and also with C. columna-alba. Near Tigrillo and in the Guanillos Valley we found it in association with C. columna-alba, C. longistaminea, C. esmeraldana, and C. laui. During our visit (May/June 2001) Marlon Machado followed a single hover fly visiting open flowers of the last three species in turn.

The authors note that C. grandiflora grows in a variety of soil types and was never found in isolation but always with the species mentioned above.

Retained as a variety of C. cinerascens