by Bob Harms 

But until the very end of the 19th Century keys for Berberis/Mahonia used venation to distinguish B. nervosa (as the name implies), and otherwise made no reference to bud scales.

A photo of the 1828 herbarium sheet for B. trifoliolata, first collected by J. Berlandier (13 years before the species was named by Moricand), is available online from Missouri Botanical Garden. It leaves little doubt that the bud scales of that species are persistent (but small). [If this link does not produce an image page, then go to their species search page and enter "Mahonia trifoliolata," and select the image from the resulting page.]

Detail from Missouri Botanical Garden photo of Berlandier's B. trifoliolata.

Moricand 1841, who cites Berlandier's specimen, noted B. trifoliolata's persistent bud scales (p. 113):

Les bourgeons sont enveloppés d'écailles d'un rouge noirâtre, pointues, imbriquées, qui sont les bases des pétioles avortés, et qui persistant à la base des rameaux.
The buds are enveloped by scales of a dark red color, acute, imbricated, which are at the base of aborted petioles, and which persist at the base of the branches.

Moricand, T. 69, branch detail.

Howell 1897 (pp. 27-28; and again in 1903) uses venation in his key, but provides bud scale details for his northwestern species; e.g., for B. nervosa: "bud scales long-acuminate, 10-12 lines long, persistent, becoming dry and rigid."

In contrast with more regional flora, Gray's 1895 ternary key (pp. 68-70) represents a major shift toward the use of bud scale size and persistence. His key, interestingly, does not mention venation and B. nervosa (p. 70) is described as "somewhat nervose–veiny."

* ... bud scales short and small, somewhat persistent on the axillary spurs, which bear fascicles rather than racemes
     [=> B. trifoliolata]

** ... bud scales ... deciduous: flowers in erect and commonly fascicled racemes
     [=> other western Berberis species, including B. swaseyi &ndash for which Gray probably did not have had bud scale information]

*** ... bud scales large, coriaceo-glumaceous and persistent
     [=> B. nervosa]

Fedde 1901 divided Mahonias into four sections (Gruppe), one of which was Longibracteatae – for its long, thick, glumaceous inflorescence bracts – including B. nervosa and B. japonica (= B. bealei, now naturalized in the U.S.). He assigned our southwestern species to the section Horridae, with inflorescence bracts described as "bractearum parvarum squamoidearum triangularium acuminatarum" [small, scale-like, triangular, acuminate bracts (gen.)](p. 77). An identical description is given for his group Aquifoliatae, which includes the other North American species of the West. No mention is made of persistence.

Ahrendt's 1961 monograph closely followed Fedde's classification, but added a major division of Mahonias into two Groups based on inflorescence bracts, adding persistence as a diagnostic feature (p. 297):

Bracts of the inflorescence persistent and long, (1-) 1.5–4 cm.      Group ORIENTALES
     [=> B. nervosa, B. bealei]
Bracts of the inflorescence deciduous and short, 2–5 (-8) mm.      Group OCCIDENTALES
     [=> other American Mahonias]

American taxonomic treatments of Berberis in the 20th Century tend to fall into two groups based on regional coverage. (1) Areas without B. nervosa (i.e., Texas, New Mexico, Arizona) do not mention bud scales; (2) other areas (i.e., California and the Northwest) present bud scale features, both length and persistence, either in keys or descriptions. Species other than B. nervosa were earlier categorized as 'deciduous' without qualification. More recent treatments - with the exception of Whittemore's FNA key - have felt some necessity to qualify the degree of deciduousness.

As noted above, Whittemore and Williams both determine the species of the Horridae section to be 'deciduous'/'generally deciduous.' This conflicts with my own observations for B. trifoliolata, B. swaseyi, B. haematocarpa, B. nevinii, and B. fremontii which indicate that they are quite similar in the persistent bud scales of their short shoots. Indeed the short shoots of these species tend to consist of tightly fascicled sequences of bud scales and petiole bases, formed over many years.

B. swaseyi short shoots with bud scales of many years.

The literature for B. trifoliolata and B. swaseyi thus presents a wide range of views, and with the exception of Moricand, incorrect:

• Discussion of the terms persistent and deciduous.
• The persistent bud scales of Berberis in Central Texas.