Pennywort (Hydrocotyle) is a fast-growing, semi-aquatic plant known for its distinctive, coin-shaped leaves. This adaptable species thrives in various environments, ranging from fully submerged aquatic settings to consistently moist terrestrial gardens. Due to its appealing foliage and ability to form dense ground cover quickly, pennywort is frequently used in landscaping, water features, and aquariums.
Understanding Pennywort’s Preferred Conditions
The defining characteristic of pennywort is its requirement for continuous moisture, making it highly versatile. It can exist as an emergent plant along pond margins, fully submerged in an aquarium, or in damp, bog-like terrestrial soil. The plant uses runners that creep along the substrate to efficiently absorb moisture and nutrients from its surroundings.
Pennywort performs best in bright, indirect light or partial shade. While it tolerates full sun if kept consistently wet or fully submerged, intense afternoon light can scorch the delicate leaves. In aquatic settings, moderate to high light encourages a compact growth habit, preventing weak, elongated stems. The plant flourishes in warm conditions, generally between 65 and 85 degrees Fahrenheit.
Pennywort benefits from a nutrient-rich substrate but is not overly demanding. For terrestrial setups, a rich, muddy soil that retains water mimics its natural marsh habitat. In aquatic use, it can be rooted in fine gravel or sand, or attached to hardscape, as it readily absorbs nutrients from the water column. Many Hydrocotyle species can grow effectively without a deep root system, making them suitable for shallow water planting.
Preparing Your Plant Material
Successful planting involves selecting healthy cuttings or divisions from established runners. Pennywort naturally propagates via horizontal stems (stolons) that creep along the surface and produce new plantlets at nodes. A viable cutting must include at least one node, as this is the point where roots and new leaves emerge.
Use clean, sharp scissors to snip a section of the runner that includes newly formed leaves. While cuttings without established roots will root successfully, those with developing root structures will establish themselves more quickly. Ensure the cutting is long enough to anchor into the substrate, preventing it from floating away in water environments.
If acquiring pennywort from an aquatic store, thoroughly clean the material before installation. Gently rinse away any remaining sterile gel or debris from the roots and leaves using dechlorinated water. This cleaning prepares the plant for immediate nutrient uptake and prevents the introduction of unwanted substances or pests.
Step-by-Step Planting Instructions
The planting method depends on whether the pennywort will be grown terrestrially or aquatically, but the goal is always to secure the nodes into the substrate.
Terrestrial Planting
For planting directly into damp soil, create a shallow indentation in the muddy substrate. Lay the runner horizontally, pressing the nodes firmly into the soil while leaving the leaves exposed above the surface. Space the cuttings six to eight inches apart to achieve dense ground cover quickly. Pressing the nodes encourages immediate root formation and anchors the plant. Lightly mist the area after planting to settle the soil around the nodes.
Aquatic Planting
In aquatic settings, anchoring the plant is the primary concern. For marginal planting, place rooted cuttings into planting baskets filled with heavy loam soil or gravel. Submerge the basket so the leaves are just above or slightly below the waterline. For full submersion in an aquarium, use fine-tipped tweezers to gently push the stems into the substrate, ensuring the nodes are buried while the leaves remain clear.
Container Planting
If growing pennywort in containers for easier management, select a pot without drainage holes or use a standard pot placed within a sealed saucer. This setup maintains constant water levels. Plant the runners just beneath the surface of the potting mix, which must be kept saturated at all times. This method is useful for containing aggressively spreading varieties, allowing for easy removal or trimming.
Long-Term Maintenance and Growth Management
Consistent watering is the most important factor for maintaining healthy pennywort, especially for terrestrial plantings. The soil must never be allowed to dry out completely, which quickly leads to leaf browning and plant death. For potted specimens, maintaining a shallow layer of water above the soil line ensures continuous moisture.
Due to the plant’s fast growth rate, regular trimming and pruning are necessary to maintain its appearance and prevent it from smothering neighboring plants. In aquatic environments, runners that spread too far can be trimmed back at any node. These trimmed pieces can be immediately replanted to thicken the existing mat or used to start new colonies.
Pennywort does not typically require heavy fertilization when planted in rich soil or an established aquatic environment. If growth appears stunted or foliage is pale, apply a balanced, water-soluble fertilizer diluted to half-strength every four to six weeks during the active growing season. A comprehensive liquid fertilizer supports robust growth for aquatic plants.
Managing the plant’s spread is a continuous task, as its prolific runners can quickly take over an area. Regular removal of unwanted runners is the most effective way to control its footprint. Promptly snipping any stray stems that cross designated boundaries will keep the plant contained and prevent it from becoming invasive.