(1) Alisma

A perennial herb, 15 to 100 cm tall. Roots are fibrous, with shortened root heads. The leaves are basal, with a long stalk, and the base is sheath-shaped; the leaves are oblong to broadly ovate, with entire margin. The scape is erect; the inflorescence is large, conical, umbrella-shaped, with whorled branches, usually 3 to 8 whorls; flowers are bisexual; 3 sepals, broad ovate, persistent; 3 petals, white, obovate.

Achenes are obovate, flat, with 1 to 2 grooves on the back. The 1st to 3rd leaves of the seedlings are strip-like lanceolate, sessile, with a thick short leaf sheath at the lower part, and a membranous edge; the 4th to 6th leaves are ovate-lanceolate, with obvious feather veins and a long stalk.

(2) Dwarf Arrowhead

Perennial herbaceous plant. It has underground transverse rhizomes, the apex of which expands into a bulbous tuber. The leaves are basal, strip-shaped or strip-lanceolate, with blunt apex, attenuate base, slightly thicker, and obvious network veins. The scape is erect. Inflorescence paniculate and umbrella-shaped. Achenes are broadly obovate, flat, with narrow wings on both sides, and unevenly serrated wing edges.

(3) Sagittaria spp.

The underground rhizomes run sideways and the apex expands into a corm. The stem is very short and bears many alternate leaves. The leaf shape is usually triangular and arrow-shaped. Racemes, with 3 to 5 flowers on whorls, unisexual, with female flowers in the lower part with short stalks and male flowers in the upper part with slender pedicels. The aggregate fruit is round-headed, about 1 cm in diameter. Achenes obliquely obovate, 3 to 5 mm long, flat. Cotyledons are unearthed and needle-shaped. There is 1 primary leaf, alternate, linear-lanceolate.

(4) Duckweed

Annual herb. Overall smooth and hairless. Stems erect or slanting upward. Basal leaves have long stalks, cauline leaves have short stalks, and the base is sheathed; leaf shape and size are variable, usually ovate or ovate-lanceolate. Inflorescence racemose axillary. Capsule oblong. The primary leaves of seedlings are lanceolate, with a tapered apex and entire edge; after emerging from the water, the leaves gradually become oval.

(5) Yujiuhua

Yujiuhua is similar to duckweed. The differences are: the plant height of Yujiuhua is 20-40 cm; the leaves are oval and heart-shaped, larger; the inflorescence is terminal, with many flowers and a long pedicel. Concentrated in Northeast China and Hebei, Shanxi, Shaanxi, Henan, Jiangsu, Anhui and other places.