1a. Plant a shrub or small tree to 5 m tall; stems, branches, petioles, and rachises with stout prickles ... A. elata

1b. Plant herbaceous or suffruticose (woody at the base but remaining herbaceous above), stem unarmed or bristly towards the base ... 2

2a. Plant acaulescent, the peduncle and a single leaf arising from the rhizome (base); inflorescence of (2)3(7) umbels, the stalks of all umbels of equal (subequal) lengths and originating from a single point at the top of the scape ... A. nudicaulis

2b. Plant caulescent, the peduncles and multiple leaves arising from the stem; inflorescence of (2)5-many umbels; the stalks of the umbels of varying lengths and originating from multiple points along the stem and/or rachis ... 3

3a. Inflorescence a raceme of 2-15 umbels; leaves bipinnate; stem bristly towards the base ... A. hispida

3b. Inflorescence a compound panicle of 15-many umbels; leaves with three primary divisions that are each pinnately compound; stem unarmed ... A. racemosa