Solanum triflorum
2n=2x=24 (Moscone 1992; Moyetta et al. 2013).
Solanum triflorum is native to the Americas with an amphitropical distribution between temperate South and North America. Introduced outside its native range in Europe, South Africa and Australia, probably with agricultural seed or wool waste. It grows across a wide range of habitats, along road sides, sandy soils, in cultivations, and in salt plains; between 0 - 2,300 (-2,900) m elevation in its native range, between 0 - 1,800 m in the introduced range.
Old World: Australia: cut-leaf nightshade (Walsh and Entwisle 1999), three-flowered nightshade (Harden 1993); United Kingdom: small nightshade (Stace 2010).
Uses. None recorded; a weed of agriculture.
New World:
Preliminary conservation status (IUCN 2016). Solanum triflorum is a weedy species that is invasive where introduced; it has a large EOO and can be assigned a preliminary status of LC (Least Concern; Table 7 in Sarkinen et al. 2018). The EOO based on native range only is also very large (19,993,876 km2), mainly due to the disjunct distribution between North America and southern South America.
Solanum triflorum is a weed of agricultural areas, and appears not to spread aggresively based on collection numbers (see Knapp 2017). It is easily distinguished from other species in the Old World by its usually deeply lobed leaves that are often pinnatifid, but are sometimes only shallowly lobed (see van Ooststroom 1966; description of var. dentatum), the usual presence of a bracteole in the inflorescence, very narrowly elliptic buds and berries with > 30 stone cells per berry.
In its native range S. triflorum has a very large range of berry sizes; most introduced material has larger berries, but it is possible we have not seen material that has the smaller berry size from the Old World. There is also large variation in the indumentum and leaf shape in S. triflorum in its native range (Subils 1989), some of which can be seen in the Old World material. This variation is likely caused by environmental factors, and has no taxonomic relevance (Subils 1989).
The varieties of S. triflorum described by Hooker (1837) were described from plants collected on the second Franklin Expedition of 1825-1827, whose principal botanist was John Richardson and assistant botanist Thomas Drummond. William J. Hooker saw the material while he was at Glasgow, and two specimens at E were originally from there; the material from the expedition eventually came to the Natural History Museum (BM), but some is also held at K. We have selected as the lectotype of var. minus the sheet labelled “S. trifidum β” (= var. minus) at E (E00526685) which has tiny plants, and consider the small plants (also labelled “β” and on a sheet together with larger plants with a separate label) at BM (BM000934744) as isolectotype material. The sheet at K (K001159656) has both small and large plants mounted on it, and is labelled “S. triflorum α & β”, but here the small plants are labelled” α”; we think these are mis-labelled at K, and are actually part of what Hooker was recognising as var. minus (his β). We select the large plants (BM000934745) as the lectotype of var. majus, and assign the large plants on the K sheet (K001159656) as isolectotype material.