Below you can find the Species of this plant are the most common cause of hay fever in the u.s. Jeopardy Words Answer. The answer to Species of this plant are the most common cause of hay fever in the u.s. has 7 letters. This clue belongs to the Botany category and is part of Jeopardy Word Level 921. If you scroll near the bottom you will find other clues and answers part of level 921