Hydrilla verticillata (L.f.) Royle

Description

Hydrilla verticillata is a submerged freshwater aquatic herb, usually growing completely underwater and forming dense underwater mats. It is a perennial herb with slender, flexible stems that may reach 1–3 m in length depending on water depth and nutrient availability. Stems are highly branched, cylindrical, and often rooted in the substrate through delicate rhizomes and tuber-like structures. Leaves are simple, sessile, and arranged in whorls (verticillate arrangement) around the stem, usually in groups of 3–8 leaves per node. Leaves are linear to lanceolate, approximately 0.5–2 cm long, with serrated margins and a distinct midrib. The leaf surface often bears small spines or teeth, giving a rough texture. Leaves are usually bright green but may become reddish-brown under stress or high light conditions. Flowers are unisexual and very small, produced underwater or at the water surface. The species is generally monoecious or dioecious, depending on population. Male flowers are tiny and detach from the plant, floating to the surface where they release pollen. Female flowers are attached to long slender stalks and may reach the water surface for pollination. Flowers possess three sepals and three petals, with petals usually white and very small. Fruits are rarely observed and develop as small cylindrical capsules containing numerous tiny seeds. Vegetative reproduction is extremely important through fragmentation, turions, and subterranean tubers, enabling rapid spread and survival under unfavorable conditions.

Diagnostic Characters

Distribution

Phenology

Where it grows on campus

Taxonomic Notes

Hydrilla verticillata belongs to Hydrocharitaceae, a family of aquatic monocots characterized by Submerged aquatic habit, Whorled leaves, Reduced flowers, Vegetative reproduction. It is often confused with Egeria densa and Elodea canadensis.