The term 'forest plant' can be broken down into three crossword solutions: FERN (4 letters), Tree (4 letters), and TREES (5 letters). Ferns are a type of vascular plant that reproduce via spores and have fronds, or leaf-like structures. TREES are woody plants that have a single trunk and can grow to great heights. TREES are the most common type of forest plant. Finally, TREES are a collective term for multiple TREES that grow together in an area. All three of these terms are associated with forests and the plants that inhabit them.