**Background:** Slender nightshade (Solanum nigrescens Mart. and Gal.) is a wild, perennial, woody shrub distributed at altitudes of 1500–3000 m from the southeastern United States through Central America to Chile and Argentina. In Mexico, it is found in states including Aguascalientes, Chihuahua, Durango, Jalisco, the State of Mexico, and Michoacan. Despite its traditional uses as food and medicine, the species remains underutilized and is often considered a weed in crops such as corn, sugarcane, and avocado. The authors note that few phenological studies exist for wild plants, and no prior work has systematically described the growth stages of S. nigrescens. The objective was to review the scientific literature on the species and to record its phenological development under controlled greenhouse conditions using the BBCH (Biologische Bundesanstalt Bundessortenamt und Chemische Industrie) scale.
**Methods:** A literature search was conducted across 15 databases including BASE, BHL, CORE, Europe PMC, Google Scholar, PubMed, Scopus, and Science Direct using keywords such as 'slender nightshade', 'Solanum nigrescens', 'hierba mora', and 'chiquiquelite'. For the phenological study, wild plants were collected in October 2021 from San Luis Huexotla, Texcoco, State of Mexico (19°28′14″ N, 98°51′21″ W, 2330 m elevation). Ten ripe, purple fruit were gathered from the largest, disease-free plant. Seeds were extracted, rinsed, dried at room temperature (24 °C), and sown in peat substrate in 200-cavity polystyrene trays. At 44 days after planting, seedlings were transferred to black polyethylene bags with tezontle substrate and irrigated with Universal Steiner nutrient solution. Plants were grown in a greenhouse with UVII-720 plastic (85% light transmission), average day/night temperatures of 27 °C and 16 °C, and 55% relative humidity. Phenological changes were recorded from February to September 2022 using a Samsung Galaxy A02 camera (super-macro function) and a Canon DS126621 camera connected to a Zeiss SteREO Discovery V20 stereo microscope. Images were edited with Gimp 2.10 and scaled with ImageJ. A voucher specimen was deposited in the CHAPA Herbarium (voucher number 155812).
**Key Results:** The phenological record was described across seven principal BBCH stages. Germination (Stage 0) occurred in 14 days, beginning with seed imbibition (codes 01–03), radicle emergence (code 05), and seedling emergence (code 09). Leaf development (Stage 1) involved unfolding of cotyledons and up to nine or more true leaves; the first three leaves were oval with smooth edges, later becoming serrated and pointed. Side shoot formation (Stage 2) began when plants reached 5 cm in height and had unfolded the sixth true leaf. Inflorescence emergence (Stage 5) began after bifurcation of the main shoot, with flower buds progressing from erect and merged to fully open sepals with petals visible. Flowering (Stage 6) was gradual within racemes, starting with 25% of flowers open and ending with petal wilting and dehiscence. Fruit development (Stage 7) culminated in fruit reaching up to 1.5 cm in diameter. Fruit ripening (Stage 8) began with green fruit gradually turning purple; full ripening of all fruit within a cluster occurred 143 days after the appearance of the flower bud. The plant reached 1.5–3.5 m in height, with lanceolate leaves 10–18 cm long and 7–10.5 cm wide, flowers in racemes of four with stellate corollas 8–10 mm in diameter, and globose fruit turning from green to black at ripening with purple gelatinous pulp and lenticular seeds 1–1.5 mm in diameter.
Regarding traditional uses, the paper reports that in Tehuacan Puebla, average annual consumption of the plant is 8.2 kg per family. Boiled leaves contain P (1850 mg/kg), K (17,200 mg/kg), Ca (33,500 mg/kg), Mg (6000 mg/kg), Na (180 mg/kg), Fe (240 mg/kg), Mn (335 mg/kg), Cu (10.1 mg/kg), and Zn (55 mg/kg). The plant is used medicinally in Mexico (Hidalgo, Queretaro), Guatemala, and Ecuador for headaches, sore throats, wounds, gastrointestinal infections, joint pain, and skin problems. Leaf extract inhibits Candida albicans, Helicobacter pylori, Cryptococcus neoformans, Staphylococcus aureus, and several dermatophytes. Aqueous extract of the whole plant at 0.05% concentration causes 63% mortality in Aedes aegypti larvae, while root extract causes up to 98% mortality (range 88–98% depending on season).
**Clinical Implications:** While this paper is primarily a botanical and phenological study rather than a clinical trial, it documents the traditional medicinal uses and biocidal activities of S. nigrescens that may have clinical relevance. The reported inhibition of Helicobacter pylori and Candida albicans by leaf extracts suggests potential for developing antimicrobial therapies. The presence of anthocyanins in the fruit, associated with antioxidant capacity and potential anticancer properties, may have implications for human health. The detailed phenological record provides a foundation for domestication and large-scale cultivation of this species, which could contribute to food security and diversification of food sources. The authors note that seed physical latency (hard seed coat) is a barrier to germination that must be addressed in domestication efforts.