Peperomia is one of the two large genera of the family Piperaceae. It is estimated that there are over 1,000 species, occurring in all tropical and subtropical regions of the world. They are concentrated in South and Central America, but may also be found in southern North America, the Caribbean islands, Africa, Oceania, and southern and eastern parts of Asia. The exact number of species is difficult to determine, as some plants have been recorded several times with different names, and new species continue to be discovered. Peperomias have adapted to many different environments and their appearances vary greatly. Some are epiphytes (growing on other plants) or lithophytes (growing on rock or in rock crevices), and many are xerophytes (drought-tolerant, with thick succulent structures to save water) or possess underground tubers (geophytes). Most species are compact perennial shrubs or vines. Some Peperomias have thick, waxy, succulent leaves and stems; still, others are rather delicate, with paper-thin leaves. Many species will easily sunburn, preferring filtered or indirect, bright sunlight. Most of the Peperomias have minimal to virtually non-existent root systems (species-depending), with the entire mass often being nothing more than a collection of tiny, hair-like appendages used to anchor the plant. These roots, while delicate, also enable the plants to survive in less-than-ideal conditions; however, their fragility also places them at a greater risk for root rot if water does not drain sufficiently quickly. The genus name Peperomia was coined by Spanish botanists Ruiz López and Pavón Jiménez in 1794 after their travels in Peru and Chile. Peperomia plants do not have a widely- accepted common name, and some argue that it is better to use the genus name, as is the case with genera such as Petunia and Begonia. They are sometimes called radiator plants, a name possibly coined by L.H. Bailey because many of them enjoy bright and dry environments similar to a windowsill above a radiator. Furthermore, many individuals simply refer to the many Peperomias by their individual nicknames, such as Peperomia polybotrya being called the “Raindrop Peperomia” (due to its large, drop-shaped leaves), or P. argyreia being the “Watermelon Peperomia”, due to its leaf veining and shape resembling the look of a watermelon.
Description Peperomias vary considerably in appearance (see gallery below) and there is no universally accepted method of categorising them, although three main groups can be distinguished. Most species are compact and usually do not exceed 30 cm (12 in) in height. First are plants with decorative foliage, which often grow in rain or cloud forests as epiphytes. They are adapted to living in small shady crevices on, for example, trees, with small root systems. As they do not have access to ground water they are typically succulent to a certain degree, which in many species shows as thick, fleshy leaves which have a waxy surface and are sometimes rippled. The leaves may be oval with the leafstalk at or near the center of the leaf blade, or they may be heart-shaped or lance-shaped; their size varies from 2.5–10 cm (1–4 in) long. They may be green or striped, marbled or bordered with pale green, red or gray, and the petioles of some kinds are red. They also enjoy high air humidity, warm temperatures, and grow all year round. Examples include P. argyreia, P. caperata, P. nitida, P. obtusifolia, P. polybotrya, and P. scandens. The second group consists of more arid-climate, succulent peperomias, which are often found at higher altitudes. They are adapted to withstanding a long warm season followed by a colder winter and very little rainfall. They store water both in their stout stems and in their succulent leaves, which typically form a sort of “tube” or “burrito”, appearing U- or V-shaped in cross-section, often with epidermal windows on the top-side. P. columella, P. ferreyrae, P. graveolens and P. nivalis fall into this category. The third group contains geophytic peperomias. These plants have leaves that fall off in the colder dry season, survive due to their underground tubers, and grow the leaves back as more rain falls. Examples include P. macrorhiza, P. peruviana, and P. umbilicata. Currently just under 50 species of geophytic peperomias are known, but new ones continue to be discovered. Peperomia flowers are typically unnoticeable, growing in cordlike spikes, although there are some exceptions, such as P. fraseri. Most peperomia flowers seem odorless to humans but some carry a musty or even unpleasant odor, such as P. graveolens. The fruit is a berry that eventually dries out and shows the tiny pepper-like seed.
Species
There are over a thousand Peperomia species, although the exact number is unclear as some plants have been recorded several times with different names (c. 3,000 names have been used in publications) and new species continue to be discovered. At the moment [when?], Catalogue of Life lists around 1,400 recognized species.
Distribution Peperomias are found in tropical and sub-tropical regions around the world. Northern South America and Central America host the largest number of species, but peperomias can also be found in Africa, southern Asia, and Oceania. The exact number of peperomia species continues to change as new plants are discovered and some distinct plant names, perhaps catalogued in separate geographical regions, are realised to describe the same species. Therefore, the table below gives only a rough overall impression of the worldwide distribution.
Note that many peperomias are found in wide overlapping regions, for example everywhere in tropical America or Asia, and so may have not been included in the species count for individual areas.
Peperomias and humans
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