Both Cirsium
Cirsium texanum vs Cirsium undulatum
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, 3 times. We publish the rate, and then we tell you what actually separates them.
Side by sidefigs. a and b
Cirsium texanum
Texas Thistle
Cirsium undulatum
wavyleaf thistle
How often our model gets it wrong measured, not estimated
| When the plant was | The model said | How often |
|---|---|---|
| Cirsium undulatum | Cirsium texanum | 3 of 18 (17%) |
Measured on 38,949 openly licensed, research-grade photographs. Full method and dataset.
What actually separates themon the record
| Family | Both Asteraceae. The family does not separate them. |
|---|---|
| Genus | Both Cirsium. Congeners, which is why this is hard. |
| Flowering | Peaks in August versus July. If the plant is in flower, timing helps. (n = 1,110 and 486.) |
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.