Opuntia orbiculata

Salm-Dyck ex Pfeiffer, Enumeratio diagnostica cactearum hucusque cognitarum 156, 1837

HerbariumHerbarium; Herbarium; Herbarium; Herbarium; Herbarium (All herbarium specimens were submitted  as O. engelmannii, but they are O. orbiculata)

Details

Opuntia orbiculata may reach 3-ft tall, but exceptional plants may be twice as tall. It is often noticeably wider than tall for a large plant. The cladodes are thick and may be 12-inches wide, or they may be smaller. Cladodes may be nearly circular (orbicular), but they may be spatulate, oval, obovate, or even obdeltoid. Often, plants have a bluish look to them, but this is not determinative. In clement growing conditions, the plants make close-branching shrubs. In drier locations the plants may be short, prostrate, and spreading; they may even have trailing prostrate branches. Spines are variable, but are whitish or yellowish and can be lightly curved or straight. O. orbiculata occurs in OK, TX, NM, AZ, NV, and northern Mexico. It may occur in the mountains of southeastern CA. The authors have not observed it in UT. See a table comparing O. engelmannii with O. orbiculata. Read the original description from 1837. O. orbiculata is diploid.

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Dave Ferguson writes:

Details may be lacking, but evidence supports the name, Opuntia orbiculata, for plants on this page. First, the name (O. orbiculata) is valid, but it has a confused history. Material seen by Britton and Rose was assumed by them (and I have no reason to doubt they were correct) to be the same material that was named by Salm-Dyck. It was supposed to be from Brazil (if I recall correctly), but Britton and Rose realized that this was in error and that it had to be from North America, likely northern Mexico. Nothing similar occurs in South America.

Based on the bits of information I’ve been able to put together as well as the description of Britton and Rose, the plants shown on this Web page are correctly identified. There really aren’t any other candidates that fit. See the discussion and description by Britton and Rose, 1919. 

However, this uncertainty about the name suggests tentative use for now. If this name should be thrown out, the name, O. dillei (Griffiths, Annual Rep. Missouri Bot. Gard. 20: 82-83, 1909), was given to nearly spineless plants of the same taxon, and there is no ambiguity about that name (except for Benson’s incorrect belief that it was a hybrid).

As is typical of most Opuntia species, the plants are variable, and while many pads on many plants are nearly orbicular (circular), this is not a totally diagnostic trait. Oval, obdeltoid, obovate, and even spatulate pads are common. Some pads may even have pointed ends. Pads are thick or thick appearing and fleshy seeming, more so than is the case in O. engelmannii or O. lindheimeri
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