A pepper plant is a woody-stemmed perennial shrub with simple alternate leaves, five-lobed flowers and a fruit that botany classes as a berry. Knowing the parts pays off twice: you diagnose faster, and you can name the species from a flower and a seed without waiting for a pod to ripen. The single most useful fact in this article is that capsaicinoids form in the epidermal cells of the placenta and the interlocular septum, not in the seeds.
Roots
Germination sends out the radicle, which becomes the primary root. In undisturbed ground that root drives a taproot down. Transplanting almost always breaks the tip, and the plant compensates with a dense fibrous network in the top 12 to 18 inches (30 to 45 cm). Lateral roots spread outward from the primary axis, and root hairs, single-cell extensions of the root epidermis, do nearly all the water and nutrient absorption. Root hairs are fragile and short-lived, which is why a root ball handled roughly produces a week of wilting that has nothing to do with watering. Pepper stems also throw adventitious roots from buried nodes in humid conditions, the same capacity that makes stem cuttings work.
Stem, nodes and branching
The main stem carries xylem, which moves water and dissolved minerals upward, and phloem, which moves sugars in both directions. That division explains blossom end rot: calcium rides the xylem only, so it cannot move back down into fruit once the transpiration stream slows. Nodes are the points where leaves, buds and flowers emerge, and internode length records the light the plant received. Short internodes mean strong light; long pale internodes mean the fixture sat too far away. Axillary buds sit in the angle between petiole and stem, and each can become a branch or a flower. Most peppers fork at a Y, and the flower that sits in that first fork is the terminal flower growers usually pinch off to build a larger plant.
Leaves
Pepper leaves are simple and entire: one blade, no leaflets, smooth margins. The blade catches light, the petiole positions it, and the veins supply it. Stomata concentrate on the underside, where they regulate gas exchange and transpiration. That location has a practical consequence beyond water loss, since Leveillula taurica, the fungus behind pepper powdery mildew, grows inside the leaf and pushes its spore-bearing structures out through those stomata. The white bloom appears underneath while the top of the leaf shows yellow blotches, and the diagnosis chart explains why that gets misread as downy mildew. Trichomes, the hairs on leaf and stem surfaces, reach their densest in C. pubescens, whose epithet means downy.
Flower structure
A pepper flower hangs or stands on a pedicel. The calyx, a whorl of fused green sepals, protects the bud and persists as the cap on the finished pod. The corolla carries five to seven lobes, white in most species. Five stamens surround the pistil, each a filament topped by an anther that releases pollen through terminal pores. The pistil has three parts: a sticky stigma, a style, and an ovary that becomes the fruit. Peppers self-pollinate, but they are not strictly selfers. Published natural cross-pollination rates in Capsicum annuum run from roughly 7 to 65 percent depending on cultivar, pollinator pressure and how far the stigma protrudes past the anthers. A long exserted stigma sits outside the pollen cloud and picks up whatever a bee brings.
What can a flower tell you about the species?
| Feature | C. annuum | C. chinense | C. baccatum | C. frutescens | C. pubescens |
| Corolla color. | White, rarely purple. | White to greenish white. | White. | Greenish white. | Purple, rarely white. |
| Corolla markings. | None. | None, rarely faint green. | Green or yellow spots at the base, diagnostic. | None. | Purple throughout. |
| Flowers per node. | 1, rarely 2 to 3. | 2 to 5, up to 7. | 1 to 2. | 2 to 3. | 1 to 2. |
| Calyx at the pedicel junction. | No annular constriction. | Strong annular constriction, the species marker. | No constriction; 5 prominent teeth. | No constriction. | No constriction; 5 long teeth. |
| Seed color and coat. | Tan to straw, smooth. | Light tan, smooth. | Tan to yellow, smooth. | Pale tan, smooth. | Black and wrinkled, unique among cultivated peppers. |
| Leaf and stem hairs. | Sparse. | Sparse; leaves often crinkled. | Sparse; long petioles. | Sparse. | Dense and obvious to the touch. |
Two of those rows settle most identification arguments on their own. Black wrinkled seed means Rocoto or another pubescens, and nothing else cultivated produces it. A ring-shaped groove where the calyx meets the pedicel means C. chinense, and its absence rules the species out. Yellow-green spots at the corolla base mean C. baccatum. The flower guide by species works through the wild species as well.
Fruit structure
The pod wall, the pericarp, has three layers: exocarp as the outer skin, mesocarp as the flesh, endocarp as the lining. Inside, septa divide the cavity into locules, usually two to four, and the placenta runs down the center bearing the seeds. Wall thickness separates a bell from a cayenne and decides whether a variety dries well or rots first. At the top, the calyx sits over the shoulder and the pedicel joins the plant. An abscission zone forms at that junction as the pod finishes, which is why a ripe pepper releases with a light twist. Wild Capsicum pushes this further with deciduous pedicels that drop pods on contact, an adaptation for bird dispersal; cultivated types hold on.
Where is the capsaicin in a pepper?
In the placenta and the septum, not the seeds. Capsaicinoid synthesis happens in the epidermal cells lining the interlocular septum and placenta, and the compounds accumulate in subcuticular cavities that raise visible blisters on the placental surface. Stewart and colleagues traced this localization while mapping the Pun1 locus that governs pungency in C. chinense. The Chile Pepper Almanac puts the distribution at roughly 90 percent of total capsaicinoids in the placenta, 6 percent in the septa, 4 percent in the pericarp and under 1 percent in the seeds. Seeds taste hot only because they sit against placental tissue and pick up the oil. Scraping seeds out of a pod reduces heat mainly by removing the white ribs they cling to, so scrape the ribs deliberately if mildness is the goal. The capsaicinoid article covers the chemistry.
Seed anatomy
A pepper seed is flat, round and roughly 3 to 5 mm across. The testa, a tough seed coat, encloses the embryo. The embryo holds the radicle, the future root, and the plumule, the future shoot, with two cotyledons folded alongside. Germination is epigeal: the hypocotyl straightens and lifts the cotyledons above the soil, where they green up and photosynthesize until the first true leaves take over. Pepper seed retains a thin endosperm layer that supplies the embryo through that transition. The hilum, a small scar on the seed edge, marks where the seed attached to the placenta. For the physiology behind all of this, see botany for pepper growers.
Sources & Further Reading
- Stewart, C., et al. Genetic control of pungency in C. chinense via the Pun1 locus. Journal of Experimental Botany 58(5), 2007.
- Zamski, E., O. Shoham, D. Palevitch, and A. Levy. Ultrastructure of capsaicinoid-secreting cells in pungent and nonpungent red pepper (Capsicum annuum L.) cultivars. Botanical Gazette 148, 1987, 1 to 6.
- Bioversity International. Descriptors for Capsicum (IPGRI, AVRDC and CATIE, 1995), the standard source for calyx, corolla and seed descriptors.
- Pacific Northwest Pest Management Handbooks. Pepper (Capsicum spp.) Powdery Mildew.
- Priest, C.T., and D.J. Austin. The Chile Pepper Almanac. Harambe Publishing, 2026. Chapters 31 and 32. Amazon