Poisonous Plants 
Agronomy 105's Weed ID
Spotted waterhemlock
Waterhemlock is a perennial plant that has large tuberous roots and a very distinct odor.
The stems of this plant are smooth and generally grow to a height of less than 5 feet.  The poisonous compound in waterhemlock was used in ancient times to kill people.  The famous drink that killed Socrates may have been laced with poison extracted from waterhemlock.  The plant is generally found along rivers, in swamps and other wet, marshy places.
The inflorescence of waterhemlock is composed of small white flowers that are borne at the tops of the plant.  The entire plant is poisonous and will affect all warm-blooded animals including humans.  Symptoms of poisoning are a frothing at the mouth, abominable pains, diluted pupils, muscle spasms, convulsions and possibly death.
Spotted waterhemlock seeds.