Fausset's Bible Dictionary
So Celsius and the learned Ben Melech explain rosh (Hosea 10:4; Amos 6:12). (See .) Gesenius explains, from the etymology, "poppy heads." Possibly many plants of bitter juice are meant. Rosh grew in grainfields rankly, and bore a berry or fruit. Deuteronomy 29:18; Jeremiah 9:15; Jeremiah 23:15; Lamentations 3:19. Not necessarily poisonous.
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Fausset, Andrew R. Entry for 'Hemlock'. Fausset's Bible Dictionary. https://www.studylight.org/dictionaries/eng/fbd/h/hemlock.html. 1949.