Key to the haplostemonous species of Graptopetalum:

1. Rosettes 2.0–8.0 cm in diameter, cespitose ........................................................................................................................................2

- Rosettes 9.0–16.0 cm in diameter, non cespitose ...............................................................................................................................4

2. Inflorescence 6.0–12.0 cm long, 2 or less branches per inflorescence, endemic to Colima ................................................ G. glassii

- Inflorescence 19.0–35.0 cm long (rarely less), 3 or more branches per inflorescence, endemic to Michoacán ................................3

3. Leaves broadly oblong, rosettes 5.0 cm or less in diameter, flowers 15.0 mm or less in diameter ................................... G. kristenii

- Leaves obovate, rosettes 6.0 cm or more in diameter, flowers 17 mm or more in diameter....................................... G. pentandrum

4. Stems more than 10.0 mm in diameter, squamose stem surface ..................................................................................... G. superbum

- Stems less than 8.0 mm in diameter, smooth stem surface ................................................................................................................5

5. Plants 40.0–87.0 cm tall, inflorescence primary branches 5–7, mean flower density per 10 cm of the scape 6–14, flowers per basal branch 7–8, flower diameter 14.9–15.9 mm, petals yellowish with conspicuous transversal red stripes, petal width 2.9–3.0 mm, filaments red, carpels abaxially rounded............................................................................................................... G. rosanevadoense

- Plants 15.0–35.0 (–41.0) cm tall, inflorescence primary branches 8–10, mean flower density per 10 cm of the scape 16–20, flowers per basal branch 3–6, flower diameter 12.9–13.1 mm, petals greenish with inconspicuous transversal red stripes, petal width 2.7–2.8 mm, filaments greenish to distally red, carpels abaxially obtuse........................................................................... G. trujilloi