The leaves of Huoxuedan are herbaceous, the leaves are heart-shaped or kidney shaped, the length of petiole can reach one or two times of the leaves, and the lower part is usually purple; the leaves of Viola are triangular or relatively slender ovate, the upper part is generally oblong, the petiole length can reach one or two times of the leaves, and the lower part is often purple.
The leaves of Viola yedoensis are triangular ovate or narrow ovate in the lower part, and longer in the upper part. They are oblong, narrow ovate lanceolate or oblong ovate.
The flower of Huoxue Dan is relatively few, usually two, rarely 4-6. The bracts are very small, only 4 mm. The calyx is a tubular structure, the disk is like a cup, and the style is slightly extended.
The flowers of Viola are large, purplish or lavender, rarely white, generally light and with purple columnar lines.
