Boyd’s Bible Dictionary:
Not the bitter, poisonous hemlock as in Hosea 10:4; Amos 6:12, but “gall,” as elsewhere
Concise Bible Dictionary:
1. laanah, “wormwood:” used only in a figurative sense for bitterness or poison (Amos 6:12). It is translated WORMWOOD (Deut. 29:18; Prov. 5:4; Jer. 9:15; Jer. 23:15; Lam. 3:15,19; Amos 5:7). It corresponds with ἄψινθος in Revelation 8:11.
2. rosh, some poisonous plant expressive of bitterness or poison (Hos. 10:4). The word is elsewhere translated “gall,” “poison,” and “venom.” The common hemlock is the conium maculatum; the water hemlock the cicuta virosa.
Cicuta Virosa