Yes, IRONWEED is a Scrabble word!

Letter values in Scrabble US: I 1, R 1, O 1, N 1, W 4, E 1, E 1, D 2.

Is it a valid word?

IRONWEED is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

any of various plants of the genus Vernonia of tropical and warm regions of especially North America that take their name from their loose heads of purple to rose flowers that quickly take on a rusty hue

Not playable in Scrabble US: VERNONIA.