Both Cirsium
Cirsium arvense vs Cirsium discolor
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 arvense
creeping thistle
Cirsium discolor
field thistle
How often our model gets it wrong measured, not estimated
| When the plant was | The model said | How often |
|---|---|---|
| Cirsium discolor | Cirsium arvense | 3 of 19 (16%) |
Measured on 38,299 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 July versus September. If the plant is in flower, timing helps. (n = 8,029 and 1,501.) |
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.