Plants of Southern California: Brickellia californica and B. desertorum
On the desert side of the southern California mountains, these two species are often hard to distinguish, and it is easy to get the wrong determination.
The Jepson eFlora key to separate these two species is:
13. Petiole 5–60+ mm; leaf blade 10–100 mm ..... B. californica
13' Petiole 1–2.5 mm; leaf blade 3–15 mm ..... B. desertorum
The key refers to actual leaves on the plant, and not to the leaf-like bracts found in the inflorescence. If one measures what look like perfectly-fine leaves in the inflorescence for B. californica, one would conclude it was a perfect B. desertorum. See measurements and discussion for one plant.
This key is also difficult to use in that actual leaves are usually no longer present when there are flowers or fruit, which is when botanists usually want to key out a plant.
More useful is the Munz 1974 key, at least for the head length:
8. heads mostly 9-10 mm high; invol. puberulous .... B. desertorum
8'. heads mostly 12-14 mm high; invol essentially glabrous ... B. californicum
Additional characteristics that discriminate these species are:
The corolla color is white for B. desertorum, and yellow-green for B. californica.
The number of pappus bristles would clearly discriminate the two species, if the FNA treatments were correct. B. desertorum is said to have 12 to 15 bristles, and B. californica to have 24 to 30 bristles. However, in just the few specimens I and others have examined after learning about this, it appears that B. desertorum has significantly more bristles than given in the FNA, at least for our plants in the Borrego Desert area.
Here are the plants of both species measured so far.
- 27, 28 and 29 bristles for a plant along SR76 on the south side of Palomar Mountain.
- (13) 16 to 22, mean of 19.5 bristles for a plant near the mouth of Henderson Canyon west of Borrego Springs.
I'll add further measurements as they are made. If you have counted the number of pappus bristles for either of these two species, I'd love to add your count to this page, with credit to you.
Copyright © 2021 by Tom Chester
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Last update: 27 December 2021