We found one dictionary that defines the word mustard trees:

General (1 matching dictionary)

1. mustard trees: Vocabulary.com

(Note: See mustard_tree as well.)

Definitions from Wiktionary (mustard tree) ▸ noun:  The toothbrush tree. ▸ Also see mustard_tree ▸ Words similar to mustard trees ▸ Usage examples for mustard trees ▸ Idioms related to mustard trees ▸ Wikipedia articles (New!) ▸ Words that often appear near mustard trees ▸ Rhymes of mustard trees ▸ Invented words related to mustard trees