Whorl Leaf Watermilfoil

Grows in thickets in lakes and ponds. Found abundantly in the Kashmir Valley lakes. Collected here in a stream in the Salt Range, Jhelum Dist. at c. 700 m.

In its terrestrial form this species may fully develop as small plants, with few leaf segments, and often set fruit better than the aquatic form.

Submerged perennial. Stem thick, up to 3 m long, simple, rarely branching, glabrous. Rhizome rooting. Leaves 20-35 mm long, pinnatisect, segments 20-35, linear and filiform. Spike 10-30 cm long. Bracts 10-25 mm long, pectinate, the lower most sterile. Flowers sessile, in whorls of (4-) 5, in the axils of bracts, the upper male, the lower female with a few bisexual ones in between. Male flower: calyx tube c. 1 mm long, lobes triangular; petals 4, oblong-ovate, 2.5-3 mm long, greenish-yellow. Stamens 8, filaments slender; anthers c. 2 mm long. Female flower: calyx as in the male; petals lacking. Ovary subglobose, c. 2 mm long, 4-locular; style short, stigmas plumose. Fruit a schizocarp. Seeds elongated, 1.5 mm long, smooth.

Plants mostly monoecious, rarely with bisexual flowers. Perennation by clavate turions. Stem robustly branched or unbranched, 50-150 cm; internodes often shorter than leaves. Submerged leaves 4-6-whorled, pectinate, narrowly ovate in outline, 3-5 × 1.5-2.5 cm; segments in 10-20 pairs, filiform, 1-2.5 cm. Inflorescence a terminal spike of 4-whorled flowers, 7-20 cm; bracts pectinate or absent. Male flowers: bracteoles lanceolate-lobed; calyx broadly campanulate, ca. 1 mm, 4-parted nearly 1/2 of way to base; petals white or greenish, obovate, 2-2.5 mm; stamens 8. Female flowers: bracteoles pectinate, 1-5 × as long as flower; calyx tubular, shortly lobed; petals greenish or white, minute. Fruit 4-loculed, subglobose, ca. 3 mm; mericarps smooth or sparsely verrucose along margins. Fl. and fr. Apr-Sep.

Distribution: Throughout Europe, Asia, N. & S. America, N. Africa.

Throughout China [Africa, Asia, Europe, North America].

Fl.Per.: July-August.

Stagnant waters, lakes, ditches, slow streams, occasionally drying ponds; near sea level to 3500 m.

Myriophyllum limosum Hectot ex Candolle.