Myriophyllum variifolium

Perennial aquatic herb; stems 30–50 cm long, to 5 mm diam., rooting at nodes in shallow water. Leaves dimorphic; submerged leaves in whorls of 4 or 5, orbicular, mostly 11–20 mm long, pectinate, with 9–15 well-spaced pinnae; emergent leaves in whorls of 5, linear to terete, mostly 8–15 mm long, margins entire or lowermost 3 or 4 denticulate. Bracteoles of male flowers ovate, c. 1.2 mm long; bracteoles of female flowers smaller; flowers solitary, sessile. Male flowers: sepals 4, orbicular to oblong, 0.6–0.8 mm long; petals 4, 2.5–3.5 mm long, yellow to reddish, caducous; stamens 8. Female flowers: sepals and petals absent; ovary 4-celled, styles sessile, stigmas white, fimbriate. Fruit cylindric, yellow-brown to pale reddish; mericarps cylindric, 1.4–1.5 mm long, truncate, smooth or minutely and sparsely papillose. Flowers Oct.–Mar.