Hygrophila Lacustris

Taxonomy & Names

• Scientific Name: Hygrophila lacustris (Schltdl. & Cham.) Nees 

• Common Name: Gulf Swampweed 

• Family: Acanthaceae (Acanthus family) 

• Synonyms: Ruellia lacustris Schltdl. & Cham. (its basionym) 

Note on Taxonomy: There is some debate among botanists. Some recent sources suggest that H. lacustris might actually be part of a more widespread, variable species called Hygrophila costata. However, it is still widely recognized as a separate taxon, particularly in resources focused on the flora of the Southeastern United States .

 Physical Characteristics

• Growth Form: An emergent or submersed aquatic plant, typically found growing upright in shallow water. It often has a "fern-like" appearance and can form dense stands .

• Height: Stems usually grow around 3 feet (approx. 90 cm) tall .

• Stems: The stems are often branching and will root at the nodes (the points where leaves attach), which helps the plant spread. They are described as square-shaped .

• Leaves: The leaves are arranged in opposite pairs along the stem. They are long and narrow (lanceolate to elliptical), roughly 9 cm long and only 10 mm wide. The foliage is typically a shade of green .

• Flowers: Small, tubular flowers bloom from summer to early fall (June to September). They are described as bluish-white and are nestled in the leaf axils (where the leaf meets the stem) .

  • Note: One source describes the flowers as "showy purple," but this is contradicted by the more detailed academic and extension service sources .

 Habitat & Distribution

• Native Range: It is native to the southeastern United States (from Georgia and Florida west to Texas) and is also found in the West Indies .

• U.S. States: It has been documented in Alabama, Florida, Georgia, Louisiana, Mississippi, and Texas .

• Preferred Habitat: As its common name suggests, it grows in wet, sunny places. You'll find it in shallow water of swamps, marshes, ponds, and along shores .

• Wetland Indicator: It is classified as OBL (Obligate Wetland) , meaning it almost always occurs in wetlands .

 Ecological Role & Adaptations

• Wildlife Value: The plant provides habitat. Its root systems can be used by macroinvertebrates, and birds may forage in patches of it . The flowers also attract pollinators like bees and butterflies .

• Salinity Tolerance: It has a low tolerance for salt. It will typically die if water salinity rises above 3 parts per thousand (ppt) .

• Erosion Control: Its root system helps stabilize sediments along shorelines .

 Aquarium Cultivation

Hygrophila lacustris is also known in the aquarium trade, sometimes under the name "Lake Hicotea" . A Chinese aquarium source provides specific care details :

• Difficulty: Moderate.

• Lighting: Requires strong light to grow well.

• Temperature: Prefers warm water between 22-28°C (72-82°F) .

• Water Parameters: Soft to moderately hard water (2-12 dH) with a slightly acidic to neutral pH (6.0-7.2).

• CO2 and Nutrients: Adding CO2 and fertilizers is beneficial for healthy growth.

• Placement: Often used as a mid-ground or background plant in larger aquariums.

 Conservation Status

According to NatureServe, its global conservation status is ranked as G5, meaning it is considered "Secure" across its range . It is not listed under the U.S. Endangered Species Act.

Summary of Key Details