Hygrophila 'Siamensis': The Beginner-Friendly Giant Hygro

The Hygrophila corymbosa 'Siamensis', often simply called Siamensis or Siam Hygro, is a large, vibrant, and incredibly popular freshwater stem plant. As a cultivar of the species Hygrophila corymbosa (Temple Plant), the 'Siamensis' is prized for its robust nature, fast growth rate, and attractive bright green, elongated leaves that grow on thick, sturdy stems. This plant is a fantastic choice for beginners looking to easily create a lush, jungle-like background.

Native to Southeast Asia (specifically Thailand, Vietnam, and Malaysia), this plant/tissue culture is amphibious and will readily grow both submerged in the aquarium and emersed (above water) in a paludarium, where it can produce beautiful purple flowers. Under strong lighting and with adequate nutrients, the leaf tips may take on a pleasant bronze or reddish hue, adding visual interest to its bright green base color. Due to its size and fast growth, it functions best as a midground or background accent in medium to large aquariums.

The 'Siamensis' is an aggressive feeder, absorbing large amounts of nutrients (including nitrates and ammonium) directly from the water column, making it a powerful tool for maintaining water quality and inhibiting algae growth in a freshwater tank.

Care & Propagation:

• Difficulty: The 'Siamensis' is considered Easy to care for, making it suitable for both novice and experienced aquarists. It is highly adaptable to a wide range of water conditions.
• Lighting: It thrives under Moderate to High light. While it tolerates lower light, high light encourages faster, bushier growth and the desirable bronze coloration on new leaves. Under low light, the plant may become leggy and drop its lower leaves.
• CO₂ Injection: Not strictly required. This plant will grow quickly in a non-CO₂ setup, but adding CO₂ will significantly boost its growth rate and lead to a more dense, compact, and lush appearance.
• Substrate & Fertilization: It benefits greatly from a nutrient-rich substrate (like aquasoil or root tabs) and regular liquid dosing of macro and micronutrients, particularly Iron (for color) and Potassium (to prevent pinholes/deficiencies).
• Trimming & Propagation: Propagation is simple: just perform a clean cut along the stem (a few inches from the top) and replant the top portion into the substrate. The original, rooted stem will quickly sprout multiple side shoots, leading to a much bushier, denser plant. Regular trimming is necessary to prevent it from growing out of the water and to maintain a desired shape.

Quick Facts

• Scientific Name: Hygrophila corymbosa 'Siamensis'
• Primary Common Name: Siamensis
• Other Common Names: Siam Hygro, Temple Plant, Giant Hygro
• Origin: Southeast Asia (Thailand, Vietnam, Malaysia)
• Maximum Submerged Height: 12–24 inches (30–60 cm)
• Growth Rate: Fast
• Care Difficulty: Easy
• Lighting Demand: Moderate to High
• CO₂: Beneficial but Not Required
• Placement: Midground to Background
• Water Hardness: Soft to Hard (Adaptable)
• Temperature Range: 68–82°F (20–28°C)
• pH Range: 5.5–8.0