1、 Leaf difference

The leaves of Polygonum hydropiper are lanceolate or elliptic lanceolate, 4 to 8 cm long and about 0.5 to 2.5 cm wide. The top of the leaves gradually becomes sharp, the base of the leaves is wedge-shaped, the edge is full-bodied, the two sides of the leaves are hairless, with small brown spots, and the petiole is 4 to 8 mm long

The leaves of Polygonum Polygonum are broadly ovate, ovate lanceolate or broadly elliptic, 10 to 20 cm long and 5 to 12 cm wide. The top becomes sharp gradually. The leaf base is round or subcordate, and the edge is entire

2、 Flower difference

The raceme of Polygonum hydropiper is spike shaped, terminal or axillary, 3 to 8 cm long, usually drooping, with sparse flowers and discontinuous lower part. The bracts of the flowers are funnel-shaped, 2 to 3 mm long, green. The flowers are green, with 5 deep cracks, and the upper part is white or light red

The raceme of Polygonum hydropiper is spike shaped, terminal or axillary, 3 to 7 cm long. The flowers are dense and slightly drooping. Usually, several more form a panicle, and the flowers are light red or white