Plants of Southern California: Dudleya arizonica and D. pulverulenta
I have spent most of my botanical career being confused about these two species. Hence I began photographing a number of plants whenever I came across them, so that some day I could put all those pictures together and see if I could distinguish them.
Finally, some day came, and here are some of the pictures I've accumulated over the years. All of these pictures are from San Diego County or from the very nearby Santa Rosa Plateau in southwestern Riverside County. Most of the pictures on this page are from me, but I nabbed a few from iNaturalist from other areas in San Diego County I haven't been, to get better geographic coverage.
The pictures are displayed in Table 2 below.
They are presented in increasing order of the number of leaves, since D. arizonica is supposed to have 15 to 25 leaves for a mature rosette, and D. pulverulenta is supposed to have 40 to 60 leaves for a mature rosette. Presumably, the plants near the top of Table 2 should preferentially be D. arizonica, and plants near the bottom of Table 2 should preferentially be D. pulverulenta. However, note that some of the pictures show plants without buds or old inflorescences, which are possibly immature and would be expected to have fewer leaves, and hence there probably are some D. pulverulenta lurking near the top of the Table.
The rows are numbered and the columns are lettered so a given pix can be identified by its row and column. The pix on the left in the top row is thus 1A; the one on the right is 1B.
Most of these pictures are from a group of plants at a given location, and are identified by the tag "Cohort A", "Cohort B", etc. Each cohort is color-coded so that one can quickly find the members of a given cohort. The cohort letters were assigned randomly. Presumably, all members of a cohort should be the same species. The pix nabbed from iNaturalist are not in any cohort, since each observation showed only a single plant.
I used the pictures on this page to see if I could distinguish the species, so the pictures are presented without identification here. I thought others might like to do the same exercise, so I've left this page intact. At the bottom of this page is a link to a page in which I have determined all of these pix except for one cohort that defied my attempt to categorize it.
I used the leaf differences, as given in the Jepson Manual descriptions, to determine these plants. Those differences are given in Table 1. I found that some extensions were needed to some of those characteristics. See the updated Table 1 in the link at the bottom of this page. But don't click on that link until you are finished trying to figure out the determinations yourself, if you choose to do so!
Table 1. Leaf Characteristics given in the Jepson Manual eFlora
| Characteristic | D. arizonica | D. pulverulenta |
|---|---|---|
| # of lvs, presumably for mature plants | 15 to 25 | 40 to 60 |
| shape | oblong to oblong-obovate | oblong |
| leaf tip | generally long-acuminate | acuminate to mucronate [to acute] |
| length | generally 5--15 cm | 8--25(27) cm |
| width | 1--5 cm | 3--10 cm |
| thickness | 2--4 mm | 3--10 mm |
| basal width | 1--3.5 cm | 3--8 cm |
Table 2. Photographs of Dudleya arizonica and D. pulverulenta, in order of the number of leaves per plant
| Row # | Column A | Column B |
|---|---|---|
| Row 1 |  Cohort F------------Cohort F |  Cohort F------------Cohort F |
| Row 2 |  Cohort E------------Cohort E |  Cohort A------------Cohort A |
| Row 3 | 
|  Cohort F------------Cohort F |
| Row 4 |  Cohort F------------Cohort F |  Cohort E------------Cohort E |
| Row 5 |  Cohort F------------Cohort F |  Cohort A------------Cohort A |
| Row 6 |  Cohort F------------Cohort F |  Cohort D------------Cohort D |
| Row 7 |  Cohort D------------Cohort D |  Cohort A------------Cohort A |
| Row 8 |  Cohort D------------Cohort D |  Cohort D------------Cohort D |
| Row 9 |  Cohort E------------Cohort E |  Cohort A------------Cohort A |
| Row 10 |  Cohort A------------Cohort A |  Cohort C------------Cohort C |
| Row 11 | 
|  Cohort A------------Cohort A |
| Row 12 |  Cohort C------------Cohort C |  Cohort C------------Cohort C |
| Row 13 |  Cohort E------------Cohort E | 
|
| Row 14 |  Cohort E------------Cohort E | 
|
| Row 15 |  Cohort D------------Cohort D | 
|
| Row 16 |  Cohort B------------Cohort B | 
|
| Row 17 |  Cohort A------------Cohort A |  Cohort B------------Cohort B |
| Row 18 | 
| 
|
Link to the page which has my determinations of the above pictures.
Go to:
Copyright © 2018 by Tom Chester
Permission is freely granted to reproduce any or all of this page as long as credit is given to me at this source:
http://tchester.org/plants/analysis/dudleya_pulverulenta_arizonica_pix_label.html
Comments and feedback: Tom Chester
Last update: 5 March 2018