Fox Tail Rush, also known as Rotated Fox Tail Rush, is a robust, submerged perennial herb of the family Haloragaceae and genus Myriophyllum. The rhizome is well-developed, spreading in the mud at the bottom of the water, with roots at the nodes. The stem is cylindrical, with many branches. The leaves above water are alternate, lanceolate, robust, bright green, with wider lobes. In autumn, spike-like winter buds are produced in the axils of the leaves to overwinter. The bracts are pinnately comb-like in division. Flowers are unisexual, monoecious or bisexual, solitary in the axils of the水上 leaves, without stems, shorter than the leaves. The female flowers are born in the lower leaf axils of the submerged stems: pale yellow, filaments thread-like, extending out of the corolla after blooming. The fruit is broadly ovate, with 4 shallow grooves, with the apex having remnants of the calyx and style.