Both Cactaceae
Echinocereus engelmannii vs Opuntia polyacantha
These two are not on this page because a keyword tool suggested them. They are here because our own identification model genuinely mistook one for the other, on real photographs, 4 times. We publish the rate, and then we tell you what actually separates them.
Confused 4x by our model Method published
Side by sidefigs. a and b
Echinocereus engelmannii
Engelmann's Hedgehog Cactus
Opuntia polyacantha
Plains Pricklypear
How often our model gets it wrong measured, not estimated
| When the plant was | The model said | How often |
|---|---|---|
| Opuntia polyacantha | Echinocereus engelmannii | 4 of 20 (20%) |
Measured on 38,949 openly licensed, research-grade photographs. Full method and dataset.
What actually separates themon the record
| Family | Both Cactaceae. The family does not separate them. |
|---|---|
| Genus | Echinocereus versus Opuntia. |
| Flowering | Peaks in April versus June. If the plant is in flower, timing helps. (n = 1,991 and 1,755.) |
What we do not have yet: the diagnostic morphological character that a botanist would key on, from a source we can cite. We are not going to invent one. Until we have it, this page tells you the two are genuinely confusable, how often, and what the taxonomy and the flowering data do and do not settle.