| Family | Scientific Name | Common Name | Habitat | Distribution | Image |
|---|---|---|---|---|---|
| Hydrocharitaceae | Blyxa | Blyxa |  (c) Rainforest, Wairambar - CC-BY | ||
| Hydrocharitaceae | Blyxa aubertii | Submersed in artificial impoundments. | Native of Asia, Africa, and Australia. | (c) Rainforest, Wairambar - CC-BY | |
| Hydrocharitaceae | Egeria | South American Waterweed |  (c) Cressler, Alan M. | ||
| Hydrocharitaceae | Egeria densa | Brazilian Waterweed, "Elodea", "Anacharis" | Ponds and stagnant water of streams or rivers. | Native of South America. | (c) Cressler, Alan M. |
| Hydrocharitaceae | Elodea | Waterweed |  (c) McNitt, Timothy - CC-BY | ||
| Hydrocharitaceae | Elodea canadensis | Common Waterweed | Rivers, lakes, ponds, stagnant waters of streams. | Québec west to Saskatchewan, south to North Carolina, Panhandle Florida, n. Arkansas, Oklahoma, New Mexico, and California, the southern distribution perhaps only introduced. | (c) McNitt, Timothy - CC-BY |
| Hydrocharitaceae | Elodea nuttallii | Nuttall's Waterweed, Free-flowered Waterweed | Lakes, ponds, stagnant waters of streams. | Newfoundland and Labrador and Québec west toBC, south to North Carolina, Al, Mississippi, New Mexico, and California. |  (c) Radford, Ahles and Bell |
| Hydrocharitaceae | Halophila | Seagrass |  (c) Fuller, Richard - CC0 | ||
| Hydrocharitaceae | Halophila decipiens | Caribbean Seagrass | Estuarine waters. | C. and s. peninsular Florida; West Indies, Mexico (Veracruz), Central America and n. South America. |  (c) Copeland, Alison - CC-BY |
| Hydrocharitaceae | Halophila engelmannii | Engelmann’s Seagrass | Estuarine waters. | S. Florida, west along Gulf Coast (Mississippi, Louisiana) to Texas and Mexico (Tamaulipas, Veracruz) to Central America; West Indies. |  (c) Northup, Alison - CC-BY |
| Hydrocharitaceae | Halophila ovalis ssp. ovalis | Johnson’s Seagrass | Estuarine waters. | Indo-Pacific regions; also West Indies and s. Florida (probably by introduction). | (c) Fuller, Richard - CC0 |
| Hydrocharitaceae | Hydrilla | Hydrilla |  (c) Horn, Jay | ||
| Hydrocharitaceae | Hydrilla verticillata ssp. peregrina | Wandering Hydrilla | Ponds, lakes, rivers, often locally abundant. This species has become a serious aquatic weed. | Native of Korea and adjacent ne. China. |  (c) Pogacnik, Shaun - CC0 |
| Hydrocharitaceae | Hydrilla verticillata ssp. verticillata | Whorled Hydrilla | Ponds, lakes, rivers, often locally abundant. This species has become a serious aquatic weed. | Native of China and adjacent areas. |  (c) Horn, Jay - CC-BY |
| Hydrocharitaceae | Hydrocharis | Frog's-bit |  (c) Danielson, Erik | ||
| Hydrocharitaceae | Hydrocharis morsus-ranae | European Frog's-bit | Flooded and saturated wetlands. | Native of Europe. | (c) Danielson, Erik |
| Hydrocharitaceae | Hydrocharis spongia | American Frog's-bit, Spongeplant | Swamps, marshes, ponds, pools. | Delaware and Maryland south to s. Florida, west to e. Texas, north in the interior in the Mississippi Embayment to s. Missouri and s. Illinois; disjunct around the Great Lakes (as in n. Indiana and w. New York). Reports of L. spongia as also in tropical America are based on misapplication of the name to plants that are actually H. laevigatum (Humboldt & Bonpland ex Willdenow) Byng & Christenhusz. | |
| Hydrocharitaceae | Hydrocharitaceae | Frog's-bit Family |  (c) Fleming, Gary P. | ||
| Hydrocharitaceae | Limnobium | Frog's-bit |  (c) Sorrie, Bruce A. - CC-BY | ||
| Hydrocharitaceae | Najas | Naiad, Bushy-pondweed, Water-nymph |  (c) htrommer - CC-BY-NC | ||
| Hydrocharitaceae | Najas canadensis | Northern Naiad | Lakes, rivers, impoundments. | Maine and Minnesota south to Virginia, Ohio, and Indiana; in the west in Idaho, Washington, and Oregon (at least); also in n. Europe. |  (c) Léveillé-Bourret, Étienne - CC-BY-NC, permission granted to NCBG |
| Hydrocharitaceae | Najas filifolia | Narrowleaf Naiad | Lakes. | Sw. Georgia (Jones & Coile 1988) and s. Alabama to Florida (Haynes in FNA 2000). |  © Nia Wellendorf |
| Hydrocharitaceae | Najas flexilis | Northern Naiad | Lakes, rivers, impoundments. | Newfoundland and Labrador (Newfoundland) west to Ontario, south to Connecticut, Michigan, and Nebraska; also in the west from Alberta and Saskatchewan south to Oregon and Utah; n. Eurasia. |  (c) Steven, Daniel - C, permission granted to NCBG |
| Hydrocharitaceae | Najas gracillima | Slender Naiad, Bushy Naiad | Ponds, lakes, slow-moving streams. | Nova Scotia west to Minnesota, south to North Carolina, Alabama, and Missouri; disjunct in California (where likely alien). |  (c) Graeff, Alex - CC-BY-NC-ND, permission granted to NCBG |
| Hydrocharitaceae | Najas guadalupensis var. floridana | Lakes and streams. | S. Georgia and s. Alabama south to Florida. |  (c) Bradley, Keith | |
| Hydrocharitaceae | Najas guadalupensis var. guadalupensis | Common Naiad, Southern Naiad | Lakes, rivers, impoundments. | Maine to Alberta and Washington, south to s. Florida, Texas, and California, and south through Mexico, Central America, South America; West Indies. |  (c) Watson, Ryan - CC-BY |
| Hydrocharitaceae | Najas guadalupensis var. olivacea | Lakes, rivers. | Québec, Ontario, and Manitoba south to New York, Indiana, Illinois, and Iowa. | (c) htrommer - CC-BY-NC | |
| Hydrocharitaceae | Najas marina | Holly-leaf Naiad | Brackish or calcareous waters. | Scattered in ne. and nc. North America; Florida; sw. United States, nw. United States (Freeman & Pfingsten 2021), Mexico, Central America, and South America; West Indies; Eurasia. |  (c) ÖkopatóPál - CC0 |
| Hydrocharitaceae | Najas minor | Spinyleaf Naiad | Ponds, lakes, and reservoirs, particularly where eutrophic. | Native of Eurasia. This species is apparently a rather recent introduction to North America, now widespread in e. North America. Haynes (1979) reported that it is becoming more abundant in e. North America because of its tolerance for polluted, eutrophic waters. |  (c) Spaulding, Dan - CC-BY-NC, permission granted to NCBG |
| Hydrocharitaceae | Najas muenscheri | Hudson River Naiad | Estuarine waters. | Hudson River Estuary, Delaware River Estuary, North East River Estuary. | |
| Hydrocharitaceae | Najas wrightiana | Wright’s Naiad | Blackwater streams, sloughs, freshwater marshes. | S. peninsular Florida; West Indies (Cuba); Mexico and Central America (Guatemala, Belize, Honduras). |  (c) Horn, Jay |
| Hydrocharitaceae | Ottelia | Duck-lettuce |  (c) Aravinth - CC-BY | ||
| Hydrocharitaceae | Ottelia alismoides | Duck-lettuce | Quiet waters of streams and bayous, and a weed in rice fields. | Native of Asia and Australia. | (c) Aravinth - CC-BY |
| Hydrocharitaceae | Thalassia | Turtlegrass |  (c) Montes de Oca, Joseph - CC-BY-NC, permission granted to NCBG | ||
| Hydrocharitaceae | Thalassia testudinum | Turtlegrass | Seagrass beds in estuarine waters. | E. coast of c. peninsular Florida (Indian River County) to s. Florida, north along the west coast of Florida to the Panhandle, west to Texas, thence south through Mexico and Central America to South America; West Indies. | (c) Montes de Oca, Joseph - CC-BY-NC, permission granted to NCBG |
| Hydrocharitaceae | Vallisneria | Water-celery, Eelgrass | (c) Fleming, Gary P. | ||
| Hydrocharitaceae | Vallisneria ×pseudorosulata | Aquatic. | Known from coastal and inland Florida and inland Alabama, but likely to be much more widespread. | ||
| Hydrocharitaceae | Vallisneria americana | Vallisneria, Water-celery, Tapegrass, Eelgrass | Lakes, rivers, estuaries, sounds. | Nova Scotia and Québec west to North Dakota, south to Florida, Texas, New Mexico, Arizona; south into tropical America {or is this all or partly V. neotropicalis?}. | (c) Fleming, Gary P. |
| Hydrocharitaceae | Vallisneria neotropicalis | Large Water-celery, Large Eelgrass | Spring runs; other aquatic habitats. | Florida Panhandle, s. Florida, and apparently from e. South Carolina west to Texas in the Coastal Plain; Cuba. |  © Casey Williams |
| Hydrocharitaceae | Vallisneria spiralis | Rivers. | Native of Europe, Africa, and s. and w. Asia. Introduced and invasive in the Braden River, Florida. |