1. Plant annual herbs, not climbing; flowers white or yellow; fruits green or black.

2. Plant spiny; flowers yellow, 2-3 cm wide......................Solanum rostratum

2. Plants not spiny; flowers white or creamy, less than 1 cm wide.

3. Leaves deeply lobed....................................Solanum triflorum

3. Leaves entire, toothed or wavy margined.

4. Calyces 4-6 mm long at maturity, cupping the fruit; stems with spreading hairs.............................Solanum physalifolium

4. Calyces 2-3 mm long at maturity, not cupping the fruit; stems smooth or appressed-hairy...............................Solanum americanum

Source: The Illustrated Flora of British Columbia

Note that Solanum nigrum (with two subspecies) was added to the BC flora after the publication of the Illustrated Flora, and is not included in this key. It may be confused with Solanum americanum and features overlap, but with good fruiting or flowering material these two species but may be separated as follows:

1. Corollas > 5 mm diameter, anthers 1.5 - 3.0 mm, petals whitish, seeds 1.5 - 2.5 mm, inflorescence raceme-like with an often extended central axis, fruit often dull when mature...................S. nigrum

1. Corollas ca. 4.5 mm diameter, anthers < 1.5 mm, petals whitish to faintly to strongly purple-tinged, seeds 1 -1.5 mm, inflorescence umbel-like with a very short central axis, fruit often shiny when mature.................S. americanum

2. plants subglabrous or often with appressed non-glandular hairs on the stems and leaves...............subsp. nigrum

2. plants villous with spreading glandular multi-celled hairs...........subsp. schultesii

Source: Frank Lomer, 2010.