As nouns the difference between forb and ironweed
is that forb is any non-woody flowering plant that is not a grass while ironweed is any of certain species of the genus Vernonia of forbs and shrubs.
forb
English
Noun
(
en noun)
(chiefly, ecology) Any non-woody flowering plant that is not a grass.
ironweed
English
Noun
(Vernonia)
Any of certain species of the genus Vernonia of forbs and shrubs.