The term 'Fall Flower' can be broken down into two crossword solutions: MUM (3 letters) and ASTER (5 letters). Mums, also known as Chrysanthemums, are a popular flower that bloom in the fall. They come in a variety of colors and sizes and are often used in bouquets and floral arrangements. Asters are another type of flower that bloom in the fall. They have daisy-like petals and come in a range of colors, including white, pink, purple, and blue. Asters are often used in gardens and as cut flowers.