According to the National Gardening Association, the most popular homegrown veggies are tomatoes (86%), cucumbers (47%), sweet peppers (46%), beans (39%), carrots (34%), summer squash (32%), onions (32%), hot peppers (31%), lettuce (28%), peas (24%), and sweet corn (23%). When you consider both sweet and hot peppers together, they are the second most popular homegrown vegetable in the U.S. Peppers are thought to be native to South America more specifically the areas of modern-day Bolivia and Peru. Peppers have been a part of the human diet for over 7500 years. Evidence points to the first domestication of peppers in Mexico over 6000 years ago; however, there is also evidence that they were also being cultivated in Peru, Bolivia and the Amazon basin. Christopher Columbus took pepper seeds with him back to Europe, and the species quickly spread across the continent appearing in Spanish records by 1493 and spread on to Asia and Africa. Wild peppers and all of the original cultivated peppers had some degree of heat/spiciness due to the presence of capsaicin and other related compounds (capsaicinoids). Capsaicin is present in all fleshy parts of the plant but is in highest concentration in the fruit, especially the inner white placental tissue. Removing the seeds and placenta before using hot peppers will reduce the spiciness considerably. Capsaicin is an irritant and neurotoxin to all mammals, including humans. Birds, however, are not affected by capsaicin. Seeds of wild Capsicum are often dispersed by birds who eat the fruit and pass the seeds. That also means that you can protect your bird feeder seeds from squirrels, mice, racoons, and other thieves by shaking on a healthy amount of cayenne pepper or chili powder. The mild bell pepper cultivar didn’t exist until it was developed in the 1920s, in Szeged, Hungary. Most of the edible peppers that we are familiar with belong to the Capsicum annuum species. Bell, cayenne, ancho, jalapeno, cubanelle, wax, serrano – these are all Capsicum annuum varieties. There are over 25 species of Capsicum, five of which are domesticated species that have found their way to our tables – Capsicum annuum, Capsicum baccatum, Capsicum chinense, Capsicum frutescens, Capsicum pubescens. Some estimates put the number of pepper varieties grown worldwide at over 50,000. This may be an overestimate, but just looking through any seed catalog tells you there are a lot. Most of these are in the Capsicum annuum species.

Figure 1: A variety of different pepper varieties grown by Joe Willis in New Orleans

Scoville Heat Units (SHU) The Scoville Scale was invented in 1912 by an American pharmacologist named Wilbur Scoville. Scoville devised a way of testing the pungency of chili peppers by making an extract and then diluting it with sugar water until a panel of trained tasters could no longer detect any capsaicin. The number of dilutions required to reach this point is expressed as Scoville Heat Units (SHU). Since the test depended on the inherent ability of panel members to detect the heat, it could have a wide range. Since the 1980s, pungency has been assessed quantitatively using high-performance liquid chromatography (HPLC). HPLC measures the concentration of heat-producing capsaicinoids in a standardized extract. This concentration in parts per million (ppm) is then related back to Scoville Heat Units by multiplying ppm by 16. SHU values for any pepper variety are variable due to genetic variation within a variety as well as growing conditions like climate, humidity, water availability, and soil nutrient composition. This variability can be by a factor of 10 or more. There are five levels of pungency based on the use of Scoville heat units (SHU): non-pungent (0–700 SHU), mildly pungent (700–3,000 SHU), moderately pungent (3,000–25,000 SHU), highly pungent (25,000–70,000 SHU), and very highly pungent (>80,000 SHU). More commonly used terminology is sweet (0-700 SHU); mild (700-2500 SHU); medium (2500-10,000 SHU); hot (10,000-50,000 SHU); very hot (50,000- 350,000 SHU); extremely hot (350,000-900,000 SHU); and super hot (>900,000 SHU). Pepper Anatomy Peppers are fruits and more specifically, berries. In botany, a berry is a fleshy fruit without a central pit or stone that develops from a single flower containing one ovary. Peppers are members of the Solanaceae family. Flowers, generally, are complete with five or more flower parts and the petals are partially fused. Flower color and morphology are the major ways to distinguish the 5 domesticated species.

Figure 2: Scoville Heat Units (SHU) for some familiar peppers.

Pepper Anatomy Peppers are fruits and more specifically, berries. In botany, a berry is a fleshy fruit without a central pit or stone that develops from a single flower containing one ovary. Peppers are members of the Solanaceae family. Flowers, generally, are complete with five or more flower parts and the petals are partially fused. Flower color and morphology are the major ways to distinguish the 5 domesticated species.

Capsicum annuum This species is cultivated around the world and has the greatest number of varieties and the most diversity of shapes, colors, sizes, and flavors. The spiciness may be completely absent or sweet, as with bell peppers; mild, as with Cajun belles; medium, as with jalapenos; hot or very hot, as with serranos and cayennes. Most peppers sold as ornamental peppers are in this species. 0-350,000 SHU The flowers of Capsicum annuum varieties are white, purple, or white bordered with purple with no spots on the petals. They generally have 5 petals and one flower per node.

Figure 3: Typical pepper flower with parts labeled.

Figure 4: Anatomy of the typical pepper fruit (a berry). Note the location of the placenta which contains most of the capsaicin.

Capsicum baccatum Capsicum baccatum varieties have pendulous white flowers with 4-9 petals having yellow or green dots. There is normally one flower per node. Variety names often have “aji” in the name. There are a few mild to medium varieties but most are hot. Common varieties include Aji Rico, Brazilian starfish, and Christmas bell. 2500-50,000 SHU

Capsicum chinense Capsicum chinense is a misnomer because these peppers are native to the Amazon basin and not China. Most varieties have greenish-white flowers with purple anthers with some varieties having white petals with purple spots. There are generally 5-6 petals and a ringshaped constriction on the petiole just before the fruit. There are 2 or more flowers per node. Though there are a few mildly spicy varieties, this species is known for the extremely hot varieties. Common varieties include habanero, ghost pepper, scorpion, Scotch bonnet, and the Carolina reaper. 500-1,350,000 SHU

Capsicum frutescens Capsicum frutescens varieties have white to greenish flowers with 5-6 petals, purple anthers, and no spots on the corolla. There is normally one and sometimes two flowers per node. Fruits are held erect and are easily detached from the pedicel. Fruits are very spicy. Plants tend to be very bushy in habit. The most common variety is tabasco. 30,000-900,000 SHU

Capsicum pubescens Capsicum pubescens have purple flowers and the seeds are black. Flowers are held erect and there are 1- 2 per node. Pubescens means hairy and the plants Typical pepper flower with parts labeled. Anatomy of the typical pepper fruit (a berry). Note the location of the placenta which contains most of the capsaicin. have hairy leaves. Only a few varieties of Capsicum pubescens are available, the most common being rocoto. The fruits are very hot. 50,000-350,000 SHU.

Joe W. Willis

Resources Capsaicin. 2024. Wikipedia. Capsaicin - Wikipedia Chili Pepper. 2024. Wikipedia. Chili pepper - Wikipedia Dewitt, D. and P. W. Bosland. 2014. The Complete Chile Pepper Book. Timberland Press. Dewitt, D. and J. Lamson. 2015. The Field Guide to Peppers. Timberland Press. How Do You Measure the Heat of a Pepper. 2022. National Institute of Standards and Technology. How Do You Measure the ‘Heat’ of a Pepper? | NIST Scoville Scale. 2024. Wikipedia. Scoville scale - Wikipedia Zamora, A.G. et. al. 2013. Characterization of Different Capsicum Varieties by Evaluation of Their Capsaicinoids Content by High Performance Liquid Chromatography, Determination of Pungency and Effect of High Temperature. Molecules. 2013 Nov; 18 (11): 13471–13486. Characterization of Different Capsicum Varieties by Evaluation of Their Capsaicinoids Content by High Performance Liquid Chromatography, Determination of Pungency and Effect of High Temperature - PMC (nih.gov)

Figure 5: The five domesticated species of Capsicum. Note the distinguishing differences as discussed in the text.