The classification of chillies is widely controversial. This is my attempt to discover some of the salient facts about chillies, an essential ingredient in Thai food. Since I’m not a botanist, I’m certain to offend someone or other with this post. Nonetheless, here’s my best effort at getting it correct. Comments gladly accepted: please keep it civil!

(Click on an image to see a larger version.)

Origin & Cultivation of chillies

Chillies at Khon Kaen Market

All varieties of chillies originated in Central, South and North America, primarily in Colombia, Ecuador and Mexico. The sometimes seen speculation that all chillies are descendants of an original “mother” chilli from Bolivia is unproven, called by one researcher “a highly speculative hypothesis.” (# 1.) It is possible that there are a very few Old World cultivars that are not found in the Americas. (cultivar: “a variety of a plant developed from a natural species and maintained under cultivation” – WordNetweb)

Chillies have been cultivated for millennia by Native Americans making them one of the oldest cultivated crops in the world. Chillies have played a part in Native American diets as early as ~8000 B.C.E. and were cultivated and traded as early as 6000 B.C.E.. Chillies were independently domesticated several times by several different prehistoric Native American cultures; traces have been found of this cultivation from the Bahamas to Southern Peru. At the time of the arrival of the Europeans, domestication was quite widespread throughout South, Central and North America, in virtually every soil and climate ranging from Argentina and Chile to the Southwestern United States. (# 2.)

We owe a huge debt to the Native Americans who cultivated (and continue to cultivate) chillies for thousands of years. This debt extends beyond chillies: foods first domesticated by Native Americans from an early date include corn, tomotoes, potatoes, squash, shell beans and manioc (also called cassava, tapioca or yuca – a common ingredient in Thai cooking). In 2007, five of the top twenty crops in the world (by tonnage) originated in the Americas (maize (corn), potato, cassava, tomato and sweet potato); of the top twenty-six crops, eight were crops domesticated by early Native Americas. (# 3.)

Reaching Thailand

Red Thai Chillies

Chillies made it to Europe with Christopher Columbus, returning from the New World after his 1492 voyage. Columbus was searching for a shorter route to India, source of the valuable spice black pepper. By the time of Columbus’s arrival in Cuba, there were probably hundreds of types of chilli peppers being raised. In 1492 Columbus saw some plants cultivated in Hispaniola (the second largest island in the Caribbean) by the Arawak Indians, (# 4.) who called them “axi,” which became “aji.” Chillies are a completely different botanical subclass, order and family than black pepper (see below). Nonetheless, Columbus, thinking he was in India, called them “red peppers.” He also misnamed the inhabitants “Indians.”

All chillies are of the genus Capsicum, generally used only for taxonomic discussion. (taxonomy: “a classification of organisms into groups based on similarities of structure or origin etc” – WordNetWeb) The common name comes from the Nahuatl (Aztec) “chil” or “chili”. Today, you’ll find three different English spellings for “red pepper”: chile, chili and chilli. Chile is the Hispanic spelling of the word; chili (one l) is the English (as spoken by the English) spelling; chilli (two ls) is used in Middle Eastern and Asian countries. Except when quoting, I use the spelling “chilli” (two ls) since that is Kasma’s generally preferred spelling. Columbus’s misnomer persists to this day and we still refer to chillies as chilli peppers.

After Columbus took the chillies back to Spain, they spread quite rapidly to all of Europe, Asia and Africa, carried primarily by the Portuguese. I came across two theories as to how they spread, though it does not seem to me that they are contradictory. One is that chillies spread to Asia, first via the Phillippines and then to India, China, Korea and Japan. The second is that the Portuguese began cultivating chillies in India and that they spread from there. However it happened, within 50 years of Columbus’s first voyage (by 1542) they were being cultivated in India, Japan and China. (# 5.) One primary reason that chillies spread so rapidly was because they had already been thoroughly domesticated by the Native Americans.

It’s unclear when the chili made it to Thailand – it could have been no earlier than sometime in the latter part of the 16th century. Whenever chillies did arrive, they have certainly become an integral part of Thai cuisine: the Thai people have a genius in incorporating new ingredients into their cuisine and making the result uniquely Thai. Check out Kasma’s blog Thai Food is Fusion Food.

It’s interesting that it’s now almost impossible to conceive of Thai food without chillies.

“Thai” Chillies

More chillies for sale

Perhaps the most common chilli used in Thailand is called prik kee noo meaning mouse dropping chilli and usually called “Thai chilli” in English. (See Kasma’s Thai Chillies – Prik Kee Noo.) Nonetheless, despite the fact this type of chilli is raised in Thailand and used in Thai cooking, there really is no “Thai” chilli pepper. Prik kee noo is a garden cultivar of aji, the same chilli species found by Columbus; there are dozens of cultivars of this variety of plant in the Americas. The origin of the variety called prik kee noo is now thought to be Ecuador where it has been cultivated since 7000 B.C.E.. One can find many aji cultivars in the Caribbean and Mexico that are indistinguishable from prik kee noo.

Some chillies have retained the name of their place of origin; cayenne, another garden cultivar of aji, was named for a port in current-day Suriname (in South America). Elsewhere, as chillies were traded, they were renamed and new associations, some fanciful, once they took hold became fixed in popular usage; so prik kee noo have been given a fanciful name in Thai and in English translation are called “Thai chillies,” referencing the cuisine in which they feature. This changing of names can be seen even in some scientific names: Capsicum chinense means “Chinese chilli,” even though it, like all chillies, originated in the New World; chillies had spread so quickly that Europeans erroneously believed they had originated in the Orient. (# 5c.)

Prik kee noo are also called “bird’s eye pepper” and “bird pepper” as is the chilli called chilli pequin, although they are not the same plant. “Bird pepper” must have been an irresistible name to people who saw wild birds eating the spicy red fruit with impunity (birds are not affected by the heat in chillies). Chilies are not alone in the vegetable world in attracting birds and other animals who eat them and help disperse their seeds locally. According to a book on seed dispersal, “Birds are the primary consumers and dispersers of wild chillies.” (# 6.)

Biological Name

Dried red chillies

Note: The claffication of plants and taxonomy is clearly an immense field in itself. Classification of Plants explains how plants are classified. As for chillies, W. Hardy Eshbaugh says: “Determining the place of origin of the genus and each of the domesticated species is at best a problematic exercise.” (# 1.) Another article as recently as 2007 talks of “the general chaos concerning classification of capsicum species.” (# 7.)

As mentioned before, all chillies are of the genus Capsicum, which is one genus of many within the family Solanaceae (Nightshade). The complete taxonomic classification (taken from the USDA Classification) looks schematically like this:

Kingdom: Plantae – Plants

Subkingdom: Tracheobionta – Vascular plants

Superdivision: Spermatophyta – Seed plants

Division: Magnoliophyta – Flowering plants

Class: Magnoliopsida – Dicotyledons

Subclass: Asteridae

Order: Solanales

Family: Solanaceae – Potato [Nightshade] family

Genus: Capsicum L. – pepper

Species: [various]

The letter L. following Capsicum stands stands for Linneaus, the botanist who named the plant; it seems to be often omitted when people give the botanical name. The family name, Solanaceae, means nightshade and includes potatoes, tomatoes and eggplant in addition to chillies.

There appear to be 30 or more species of capsicum (chillies). (# 8.) There can be many different varieties within each species. For example, the species Capsicum annuum (or C. annuum) contains chillies that are pungent (hot), such as Thai chillies, as well as chillies that are sweet, such as bell peppers. Genetically they are nearly identical yet a very small variation means a huge difference in the fruit. It is the amount of the chemical capsaicin (methylvanillyl nonenamide) in the chilli that is responsible for the heat (burning sensation in mouth).

Five species of chiles (though some would say those five species comprise only three species) are thought to have been domesticated independently in at least two regions of the New World: C. annuum and C. frutescens in Mesoamerica; C. baccatum, C. pubescens, and C. chinense in South America. Four species (although some would say three) are in general cultivation: C. annuum, C. baccatum, C. chinense and C. pubescens. (# 9.)

Of these four species, Capsicum annum is the dominant pepper globally; this is in part because Columbus and other explorers discovered it first, so it was the first chilli taken to Europe, from whence it spread rapidly.

An example of a variety within the species C. annuum would be glabriusculum: C. annuum var. glabriusculum:

Family Solanaceae – Potato [Nightshade] family

Genus – Capsicum L. – pepper

Species – Capsicum annuum L.

Variety Capsicum annuum L. var. glabriusculum

Dried chillies close-up

Capsicum annuum var. glabriusculum: As far as I can tell, the Thai chili belongs to Capsicum annuum var. glabriusculum. This variety is native to Colombia, Central America, the Caribbean and parts of the Southern United States, including Florida, Texas, Arizona, Mexico. Everywhere else it is found (so in Thailand, for instance) it is naturalized (“established: introduced from another region and persisting without cultivation” – WordNetweb) or is cultivated. It is thought (by some, at least) to be the progenitor of C. annuum. Some of the common names for this species as given by the USDA listing are aji, bird pepper, chile pequin and chilipiquin and cayenne pepper. One way of referring to prik kee noo would be as a Thai cultivar of aji. The cultivated Thai chilli also could be called C. annuum cultivar, or C. annuum var. glabriusculum cultivar.

I’ve been told, but been unable to verify, that the IAPT [International Association for Plant Taxonomy] has reclassified the Thai chilli as C. annuum var. poquin.

Some other chillies that belong to C. annum are: bell pepper (called simply Capsicum annuum); Jalapeño peppers (Capsicum annuum L. var. annuum); and the Tabasco pepper (Capsicum annuum L. var. frutescens (L.)). (# 9b.)

Many websites give the botanical name of prik kee noo as Capsicum frutescens. This, apparently, is out-of-date and the Thai chili is now classified as C. annuum. The current thinking seems to be that C. frutescens and C. annuum are the same species and are grouped together under C. annuum. It also appears that C. annuum was sometimes misidentified as C. frutescens in scientific literature. (# 10.) I’ve been told that IAPT [International Association for Plant Taxonomy] considers C. frutescens as outdated and that it is no longer is use there, although I’m not a member so I’m unable to verify this.

Two “Peppers”

It’s interesting to compare the scheme for black pepper (Piper nigrum), the spice Columbus was searching for, with that of chillies. (Schema is from ITIS [Integrated Taxonomic Information System].)

Kingdom: Plantae – Plants

Subkingdom: Tracheobionta – Vascular plants

Division: Magnoliophyta – Flowering plants

Class: Magnoliopsida – Dicotyledons

Subclass: Magnoliidae

Order: Piperales

Family: Piperaceae – Peppers

Genus: Piper L. – Pepper

Species: Piper Nigrum L. – Black pepper

It is obvious that the two “peppers” (Piper and Capsicum) belong to completely different botanical subclasses, orders and families. Piper nigrum is native to India. As mentioned above, members of the genus Capsicum are referred to as “peppers” by historical accident only, because Columbus did not understand what he had discovered.

Black pepper (Piper nigrum) in Thai is called prik Thai, which translates literally as “Thai pepper,” although in recipes it is correctly identified as black (or white) pepper as required by the recipe. (Note: black and white peppercorns are different forms of Piper nigrum – see Kasma’s article Peppercorns – Prik Thai.) Prior to the arrival of red peppers with the Portuguese, Thai cooking used prik Thai in their cooking, presumably arriving from India at some point. So we have the following:

• prik kee noo (literally, mouse dropping pepper) is the spicy (hot) red chilli Capsicum annuum var. glabriusculum; it is translated as “Thai chilli” in English.
• prik thai (literally, Thai chilli) is the black pepper Piper nigrum; it is translated as “black or white pepper” in English.

Chillies used in Thai cooking

This dish uses red chillies in the curry paste and fresh chillies for garnish

Some Articles Referenced

1. W. Hardy Eshbaugh in the 1993 article Peppers: History and Exploitation of a Serendipitous New Crop Discovery.”Determining the place of origin of the genus and each of the domesticated species is at best a problematic exercise. In 1983, I stated that “it appears that the domesticated peppers had their center of origin in south-central Bolivia with subsequent migration and differentiation into the Andes and Amazonia.” This is a condensation of a highly speculative hypothesis (McLeod et al. 1982). From that hypothesis Pickersgill (1989) later suggested that I (Eshbaugh 1983) argued that all the domesticated taxa arose in Bolivia. Without question, I could have stated this idea more clearly. We (McLeod et al. 1982) have speculatively hypothesized that Bolivia is a nuclear center of the genus Capsicum and that the origin of the domesticated taxa can ultimately be traced back to this area. That does not imply that each of the domesticated species arose in Bolivia. Clearly, evidence supports a Mexican origin of domesticated C. annuum while the other domesticated species arose in South America. Nonetheless, the ancestry of the domesticates can be traced to South America. While McLeod et al. (1982) have hypothesized a Bolivian center of origin for Capsicum there is no evidence for a polyphyletic origin of the genus as now understood.”
2. Three articles on early cultivation of chillies are: a. Domestication of Capsicum annuum chile pepper provides insights into crop origin and evolution; b. Americans Cultivated And Traded Chili Peppers 6,000 Years Ago; c. Precolumbian use of chili peppers in the Valley of Oaxaca, Mexico
3. From a.
   Wikipedia – Columbian Exchange; b. Foods that Changed the World (by Steven R. King, Ph.D.)
4. The Smithsonian Magazine article What’s so Hot About Chili Peppers?
5. See a: Wikipedia – Chili pepper; b. What’s so Hot About Chili Peppers? (page 2); c. Diffusion of Mesoamerican food complex to southeastern Europe (by Jean Andrews)
6. From the book Seed Dispersal: theory and its application in a changing world, edited by Andrew J. Dennis. The authors reference (Tewksbury and Nabham, 2001; Levey et. al., 2006)” for this quote.
7. T. Hietavuo Wild Capsicums & Domesticated Peppers. This article also says: “Categorizing plants can be very frustrating, and in case of peppers, it is almost a hopeless task.” Also: “The description of genus capsicum has been disputed and even partly questionable until these days. Because of this, most information sources still offer limited or downright false information about chile peppers and their backgrounds.”
8. Number of species: Genetic variability in domesticated Capsicum spp as assessed by morphological and agronomic data in mixed statistical analysis (PDF file)
9. a: Genetic diversity and structure in semiwild and domesticated chiles (Capsicum annuum; Solanaceae) from Mexico; b: Peppers – A Short Study; c: According to reference 7 above: “There are also 3 [to] 5 domesticated species depending on any given researcher’s opinion.” d. This quote us from T. Hietavuo Capsicum annuum var. annuum: “Capsicum annuum is a plant science, some degree of classification problem, because it consists of several genetically very closely related subspecies that different researchers have over the years classified as the most diverse ways. What is certain is only that, Capsicum annuum, chinense and frutescens subspecies is a common wild-stem form (C. annuum var. glabriusculum), which grows a rare region of northern South America at the southern USA.” [Note: this is a translation from the original Finnish using Google Translate.]
10. a: Bosland in Capsicums: Innovative Uses of an Ancient Crop; b. in reference 1 above there’s an extended discussion on this issue under the heading “CAPSICUM ANNUUM VAR. ANNUUM–CAPSICUM CHINENSE”.