Plants of Southern California: Dudleya arizonica and D. pulverulenta

In this version of the page, I've identified all the plants that appear to clear examples of D. arizonica or D. pulverulenta. The determinations, and the basis for each determination, are given immediately below each photograph. One cohort, Cohort E, defied my attempt to determine it. If you can do so, please let me know!

I made the determinations as follows:

This procedure identified 17 out of the 36 plants.

Interestingly, the leaf tips for all the plants in Cohort F, called D. arizonica from the obovate leaf shapes, have tips that are rounded and mucronate, which is supposedly a characteristic for D. pulverulenta, not the generally long-acuminate tip for D. arizonica. And since the leaf tips for all the plants in Cohorts A and B, called D. pulverulenta, are acute to acuminate, it seems hard to use the leaf-tip shape to determine a given plant.

Long acuminate tips are seen in Cohort D, determined as D. arizonica below. It seems odd to have two such very different leaf shapes in the same species, with the different leaf shapes found in different geographic locations.

I then used the difference in the number of leaves for a mature plant, which I considered to be one that was putting up flower stalks, and called plants with fewer than 20 leaves as D. arizonica. That included pix 7A (17 leaves) and 8A (19 leaves), both from Cohort D.

Note that if I had used the Jepson Manual range in the number of leaves, and called plants with fewer than 26 leaves at maturity as D. arizonica, this procedure would have misdetermined pix 10A, with 21 leaves, and pix 11B, with 25 leaves, as D. arizonica, even though they were previously determined as D. pulverulenta from one other member of Cohort A that had 36 leaves at flowering.

I then determined the other plants in Cohort D as D. arizonica. This included the budding specimen 15A with 31 leaves.

This determined an additional five pix, for a total of 22 out of the 36 plants.

This leaves two cohorts with all pix undetermined, Cohorts C and E.

Cohort C has three members, with 21 and 25 leaves for budding plants, and 25 leaves for the other plant. Two of the three members have long acuminate leaves, so these plants are probably D. arizonica.

Cohort E has five members, with 11, 14, 19, 25 and 30 leaves. None of the plants were budding or showed inflorescences from previous years. The leaves are mostly oblong in shape, with rounded mucronate tips, although some leaves are obovate and some have acute tips. It isn't clear to me how to call these plants.

In addition to the five members of Cohort E, there are six other pix that remain undetermined. Five are from coastal locations and so are surely D. pulverulenta. One is from Rockhouse Canyon near Clark Valley, and so is almost surely D. arizonica. I've labeled those photographs now.

This just leaves the five members of Cohort E. Nothing about those five plants tells me that they are unambiguously one species or the other. Maybe you can figure out what they are by comparing to the other pix.


Text from the previous page, with updated characteristics and some pix identified.

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. Most of the pix were taken by me; some pix were nabbed from iNaturalist, and thus are not in any cohort.

The leaf difference as given in the Jepson Manual descriptions is given in Table 1. Extensions to the given characteristics from plants in this set of pictures are given in red.

Table 1. Leaf Characteristics given in the Jepson Manual eFlora, updated with results from these Pictures

CharacteristicD. arizonicaD. pulverulenta
# of lvs, presumably for mature plants15 to 25
15 to 31
40 to 60
21 to 60
shapeoblong to oblong-obovateoblong
leaf tipgenerally long-acuminate
to rounded and mucronate
acuminate to mucronate [to acute]
lengthgenerally 5--15 cm8--25(27) cm
width1--5 cm3--10 cm
thickness2--4 mm 3--10 mm
basal width1--3.5 cm3--8 cm

Table 2. Photographs of Dudleya arizonica and D. pulverulenta, with my determinations

Row #Column AColumn B
Row 1
Cohort F-------------Cohort F
D. arizonica: obovate lvs

Cohort F-------------Cohort F
D. arizonica: obovate lvs
Row 2
Cohort E-------------Cohort E

Cohort A-------------Cohort A
D. pulverulenta, from other cohort members.
Row 3
probably D. arizonica from location at Rockhouse Canyon near Clark Valley.

Cohort F-------------Cohort F
D. arizonica: obovate lvs
Row 4
Cohort F-------------Cohort F
D. arizonica from other cohort members.

Cohort E-------------Cohort E
Row 5
Cohort F-------------Cohort F
D. arizonica: obovate lvs

Cohort A-------------Cohort A
D. pulverulenta, from other cohort members.
Row 6
Cohort F-------------Cohort F
D. arizonica: obovate lvs

Cohort D-------------Cohort D
D. arizonica, from other cohort members.
Row 7
Cohort D-------------Cohort D
D. arizonica, from 17 leaves at time of flowering.

Cohort A-------------Cohort A
D. pulverulenta, from other cohort members.
Row 8
Cohort D-------------Cohort D
D. arizonica, from 17 leaves at time of flowering.

Cohort D-------------Cohort D
D. arizonica, from other cohort members.
Row 9
Cohort E-------------Cohort E

Cohort A-------------Cohort A
D. pulverulenta, from other cohort members.
Row 10
Cohort A-------------Cohort A
D. pulverulenta, from other cohort members.

Cohort C-------------Cohort C
probably D. arizonica; see text.
Row 11
D. pulverulenta, from coastal location


Cohort A-------------Cohort A
D. pulverulenta, from other cohort members.
Row 12
Cohort C-------------Cohort C
probably D. arizonica; see text.

Cohort C-------------Cohort C
probably D. arizonica; see text.
Row 13
Cohort E-------------Cohort E

D. pulverulenta, from coastal location
Row 14
Cohort E-------------Cohort E

D. pulverulenta, from location at the Santa Rosa Plateau.
Row 15
Cohort D-------------Cohort D
D. arizonica, from other cohort members.

D. pulverulenta, from coastal location
Row 16
Cohort B-------------Cohort B
D. pulverulenta, from other cohort members.

D. pulverulenta, from coastal location
Row 17
Cohort A-------------Cohort A
D. pulverulenta: 36 lvs

Cohort B-------------Cohort B
D. pulverulenta: 39 lvs
Row 18
D. pulverulenta: 41 lvs
D. pulverulenta, from coastal location

D. pulverulenta: 44 lvs
D. pulverulenta, from coastal location


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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.html
Comments and feedback: Tom Chester
Last update: 5 March 2018