Pennywort (Hydrocotyle vulgaris)
Hydrocotyle vulgaris, or Pennywort, is a low-growing herbaceous perennial ideal for moist ground cover, thriving in wet soils.
Complete Plant Information
Overview
Hydrocotyle vulgaris, widely known as Pennywort, offers gardeners a unique, rapidly spreading ground cover perfectly suited for persistently moist or wet environments. Its distinctive character lies in its round, scalloped, penny-sized leaves borne on floating or creeping stems, creating a lush, verdant carpet near water features or bogs. This herbaceous perennial requires minimal attention, making it an excellent choice for low-maintenance landscapes where traditional lawn grasses struggle.
Valued for its ability to naturalize, Pennywort excels at covering large, damp areas quickly, rooting readily at its nodes as it spreads indefinitely. While its purplish-green flowers are inconspicuous, the attractive foliage of Hydrocotyle vulgaris provides year-round visual interest in specialized wet garden settings. Its tolerance for heavy shade combined with its love of water expands planting possibilities beyond sunny, standard perennial borders.
This resilient plant is highly adaptable, capable of forming a dense mat either creeping along the ground or floating in very shallow water systems. If you are aiming to establish cover in tough, soggy spots, Hydrocotyle vulgaris provides an effective, handsome solution that minimizes long-term cultural inputs once established.
Fast Facts
- Plant Family: Araliaceae
- Plant Type: Herbaceous perennial
- Native Range: Northern Africa, Europe
- Hardiness Zones: USDA Zones 6-10
- Size at Maturity:
- Height: 0.25-0.5 ft
- Spread: 1-20 ft
- Bloom Time: June to September
- Bloom Description: Purplish-green
- Sun Exposure: Full sun to part shade
- Water Needs: Medium to wet
- Maintenance Level: Low
How to Grow
Planting Pennywort is best achieved in humusy, consistently moist soils, though it readily adapts to bog conditions. While it prefers full sun to part shade, Hydrocotyle vulgaris is unusually tolerant of deep shade, providing excellent coverage where other plants might falter. Its adaptability means it can be placed directly in the mud at the edge of a pond or in up to two inches of standing water, functioning perfectly as a marginal aquatic.
Care for this perennial is extremely low, fitting its “Low” maintenance rating. Watering requirements are naturally met if planted in a bog or pond setting; otherwise, ensure the soil remains consistently moist. Fertilization is rarely necessary when the plant is situated in rich, moist soil, as nutrients are usually sufficient for steady growth.
A critical aspect of growing Hydrocotyle vulgaris is managing its pervasive spread. To prevent unwanted encroachment into lawns or drier garden beds, it is strongly recommended to grow this rhizomatous spreader in containers, even when sinking those containers into water features or bog gardens. This control measure maintains the aesthetic boundary of your space while utilizing the plant’s moisture-loving nature.
No significant seasonal pruning is required for Pennywort. You can trim back excess runners in the spring if the spread has become too enthusiastic for your taste. In colder zones, its herbaceous nature means it will die back in winter, leaving the root system dormant until spring warmth returns.
Landscape Uses
Pennywort shines in landscape designs focused on moisture management and naturalizing effects. Its primary functions are as a superb ground cover for pond or water garden margins and bog gardens, where its habit of floating or creeping along wet banks stabilizes the substrate. Due to its rampant horizontal growth, it is an excellent choice for naturalizing large, damp slopes or areas intended to mimic a wetland edge.
For water gardens, Hydrocotyle vulgaris creates an essential transition zone between dry land and open water. Use it to soften hard edges around small ponds, streams, or rain gardens, providing a green filter along the overflow sites. Due to its tendency to spread indefinitely, consider planting it within sunken pots or root barriers if you wish to keep its coverage confined to specific zones near pools or hardscaping.
In terms of companion planting, pair Pennywort with other moisture-loving species that can tolerate similar sun/shade gradients, such as certain sedges (Carex species) or moisture-loving ferns. This juxtaposition creates a lush, layered waterside design where the unique texture of the penny-sized leaves contrasts beautifully with taller, more upright wetland flora.
Standout Features
Flower Qualities
- Insignificant
Noteworthy Characteristics
Hydrocotyle vulgaris, commonly called pennywort, is a ground cover for moist to wet areas. Stems clad with round, peltate, short-stalked leaves (3/4” to 1.5” diameter) with scalloped edges float in very shallow water or creep along the ground, rooting at the nodes as they go. Purplish-green flowers are inconspicuous, appearing in 2-5 flowered umbels among the leaves from June through September.
Tolerances
- Heavy Shade
- Wet Soil
Potential Problems
Gardeners will appreciate that Pennywort generally faces no serious insect or disease problems in suitable growing conditions. Its primary challenge is cultural—managing its aggressive spreading habit rather than battling pests or pathogens. If the soil dries out too frequently, the foliage may become sparse or wilted, but systemic infestations are rare.
Prevention focuses entirely on placement control. If the soil remains moist or wet, the plant thrives and spreads rapidly via runners. If you observe it attempting to colonize drier areas or overly manicured beds, lift and divide the runners or ensure it remains contained within its designated habitat, often achieved most easily through the use of edging or waterproof barriers.
Frequently Asked Questions
What hardiness zones is Pennywort suitable for?
Hydrocotyle vulgaris is suitable for USDA Zones 6 through 10, thriving best when protected from deep freezes.
How large does Pennywort grow?
This plant typically reaches heights between 0.25 and 0.5 feet tall, but its spread can be significant, ranging from 1 foot up to 20 feet wide where allowed to colonize freely.
What sun exposure does Pennywort need?
Pennywort prefers full sun to part shade, but it is notably tolerant and can often thrive even in heavy shade, so long as moisture levels remain consistently high.
When does Hydrocotyle vulgaris bloom?
The purplish-green flowers of Hydrocotyle vulgaris appear throughout the growing season, specifically from June through September.
Conclusion
Pennywort (Hydrocotyle vulgaris) is an invaluable, high-impact perennial for gardeners dealing with saturated soils or water garden edges. Its low maintenance and attractive, unique foliage overcome the need for significant floral display, providing reliable matting cover. Before planting, carefully assess your site conditions and decide whether to contain this vigorous spreader or allow the beautiful Hydrocotyle vulgaris to truly naturalize your wet, marginal areas.
Companion Planting
When selecting partners for Pennywort, focus primarily on plants that share its extreme moisture requirements. Good companions include various irises, cattails (Typha), and certain large grasses that thrive in boggy conditions, such as Blue Flag Iris (Iris versicolor). Keep taller companions far enough away that they do not completely shade the Pennywort if you desire optimal growth, although Hydrocotyle vulgaris handles substantial shade well.
For container groupings, pair it with moisture-loving marginal lilies or submerged oxygenators in a unified water garden system. The creeping habit of the Pennywort acts as an excellent visual binder, uniting disparate elements planted along the pond’s perimeter while keeping its rampant runners in check using the container walls.
Propagation Tips
Propagating Hydrocotyle vulgaris is remarkably simple due to its creeping, rooting stems. The easiest method is division, often performed naturally as the plant spreads. Simply take cuttings—lengths of stem containing one or more nodes—and place them directly into moist soil or shallow water near the parent plant during the growing season. Roots will quickly emerge from the nodes, establishing new, independent plants.
Because this plant roots so easily at stem nodes, it can also be propagated simply by layering sections of the creeping stem onto damp soil and covering them lightly with a thin layer of topsoil or grit. This method works rapidly, especially if the stems are semi-submerged or kept constantly wet.
