Flora of the Hawaiian Islands
Dicotyledon Literature for Solanum americanum
Lorence & Wagner, 2020.
   Solanaceae -- The Nightshade Family Bibliography
      Solanum americanum

Common name(s): nightshade, tomato, `olohua, glossy nightshade, polopolo, popolo, popolohua (Ni`ihau)
General Information
DistributionWidely distributed in tropical and warm temperate areas, probably native to the New World, generally associated with some man-made disturbance.In the Hawaiian Islands, naturalized on Kure, Midway, Lisianski, Laysan, Nihoa, Ni`ihau, Kaua`i, O`ahu, Moloka`i, Lana`i, Maui, Kaho`olawe, Hawai`i.

Click here for detailed USGS map by Jonathan Price
Annual or short-lived perennial herb to 1.5 m tall, erect or wide spreading, straggly with age, sometimes flushed purplish; stems unarmed, sometimes angled or narrowly winged with lines of tissue from base of petiole, older stems often appearing spinescent, glabrous or sparsely pubescent with simple curved hairs.
Leaves simple, alternate, petiolate; blade ovate to ovate-lanceolate, or elliptic, greatly variable in size, 3.5–10 cm long, 1.0–4.5 cm wide, margin entire or occasionally sinuate-dentate, apex acute to acuminate, base truncate to cuneate and continued as a narrow wing along petiole; petiole (0.3–)2.0–3.8(–4.0).
Inflorescences an extra-axillary umbelliform cyme, peduncle (0.5–)1–1.8 cm long, flowers congested at apex. Flowers perfect, actinomorphic, pedicel 3‒9 mm long; calyx campanulate, tube 1‒1.4 mm long, lobes obtuse, 0.3–0.5 mm long; corolla white or occasionally purple tinged, stellate, 0.8‒0.9 cm in diameter, with a yellowish green star-shaped area at base, lobes ca. 1.5 mm wide, becoming reflexed; stamens inserted near base of corolla tube; filaments with spreading hairs on inner side, 1‒2 mm long, anthers oblong, 1.5‒2 mm long, opening by pores or short slits; ovary globose, ca. 1 mm in diameter, glabrous, style erect, 2.5‒4 mm long, pubescent in proximal part, stigma capitate, at level of anther pores.
Fruit glossy black, succulent, globose, (4‒)6‒8 mm in diameter, readily shed when ripe, sclerotic granules 0‒4, ca. 0.5 mm in diameter, pedicel erect or recurved in fruit, 13–18 mm long, not deciduous with fruit, persistent on older inflorescences; calyx lobes subequal, enlarged to 1(–2) mm and strongly reflexed.
Seeds numerous, 1‒1.5 mm long, compressed, white or tan, testa minutely reticulate.
2n = 12, 24.
Solanum americanum is a 2n = 24 diploid species (Särkinen et al. 2018) that can be easily recognized by its glossy black fruits on spreading pedicels with strongly reflexed calyx lobes (to par¬allel with the pedicel) that are somewhat papillate abaxially. In fruit, the pedicels remain on the plant after fruits fully mature and drop off, leaving behind a distinct group of tightly clustered spreading pedicels with reflexed calyx lobes; this character is easily vis¬ible in many herbarium specimens.
Nancy Khan