As previously indicated, a number of weed species are especially troublesome because they are poisonous to humans and/or animals. The table below summarizes the names, toxic compounds, and species affected for a number of important poisonous plants found in the U.S.

 

Poisonous species Toxin Symptoms of Poisoning
Larkspur Alkaloids Nervousness, staggered gait, bloat, sudden death
Lupines Alkaloids Birth defects (e.g. crooked legs), convulsions, loss of muscular control
Water hemlock Cicutoxin Sudden death
Locoweed Alkaloids, Selenium Nervousness, staggered gait, bloat, sudden death
Halogeton Oxalates Weakness, salivation, increased heart rate