Asian Water Grass, Hygrophila polysperma, is a widely cultivated aquatic plant often featured in freshwater aquariums, ponds, or bog gardens. Its vibrant green to reddish foliage creates a lush, natural aesthetic. Both novice and experienced aquarists appreciate its straightforward care and attractive appearance.
Key Characteristics of Asian Water Grass
Asian Water Grass is an herbaceous aquatic plant with a rapid growth rate. Its slender stems can reach 10-20 inches (25-50+ cm) in aquariums, and up to 6 feet (2 meters) in its natural habitat. Leaves are oval to lance-shaped, growing opposite on the stem, and are light green. Bright lighting can bring out pinkish or reddish hues in the top leaves. Native to South and Southeast Asia (e.g., India, Bangladesh, Bhutan, China), it thrives in slow-moving rivers, marshes, and flooded fields.
Cultivating Asian Water Grass
Cultivating Asian Water Grass requires suitable environmental conditions: light, water, substrate, and temperature. This plant is known for its adaptability, making it a good choice for various setups.
Lighting Needs
Medium to high lighting levels promote optimal growth and coloration. A daily photoperiod of 10-12 hours is recommended. Lower light results in slower growth, less vibrant coloration, and leggy, less dense stems. Strong lighting encourages dense growth and reddish tones.
Water and Substrate Requirements
It adapts to a broad range of water parameters, preferring slightly acidic to neutral pH (6.0-7.5), though it tolerates 5.0-8.0. It thrives in soft to moderately hard water. As a heavy root feeder, it benefits from a nutrient-rich substrate. Specialized aquatic soils provide essential nutrients for robust growth. A substrate depth of at least 1 to 2 inches (2.5 to 5 cm) allows for proper anchoring and nutrient absorption.
Temperature and Water Chemistry
It grows best in tropical temperatures (71-82°F / 22-28°C). While it can endure brief periods as low as 39°F (4°C), consistent warm water promotes health and growth. Stable water chemistry is beneficial. CO2 supplementation, though not strictly necessary, enhances growth rate, density, and leaf coloration, especially under higher light. Regular partial water changes replenish nutrients and maintain water quality.
Propagating Asian Water Grass
Propagation is straightforward, primarily through stem cuttings. It readily develops new roots from stem fragments, making multiplication easy. To propagate, cut a healthy stem portion (about 4 inches / 10 cm) just below a node, removing leaves from the bottom 1-2 inches to prevent rot. Gently insert the cutting into the substrate, ensuring secure anchoring. New roots typically form within 7-10 days, establishing a new plant.
Important Considerations for Growing
Due to its fast growth rate, Asian Water Grass requires regular trimming to prevent overcrowding and overshadowing other plants. Frequent pruning (every 2-3 weeks) encourages bushier growth and maintains appearance. This species can become invasive in natural waterways if trimmings are not disposed of responsibly, as small fragments can root and establish new colonies. Common issues include nutrient deficiencies, manifesting as yellowing or deformed leaves, especially if rapid growth outstrips nutrient availability. A nutrient-rich substrate and liquid fertilizers or root tabs can address these issues; sudden changes in water parameters or insufficient CO2 can also lead to leaf loss or stunted growth.