Hydrocotyle vulgaris aka Marsh Pennywort

Marsh pennywort is an aquatic plant that requires constantly wet to waterlogged soil conditions and should never be allowed to dry out. It thrives in poorly-drained soils and can grow submerged in up to 2-5cm of standing water, making it ideal for pond margins, bog gardens, and water features. When grown in containers, keep the soil permanently saturated or place the pot in a saucer of water to maintain consistent moisture.

Marsh pennywort is hardy in USDA zones 6-10 and can tolerate a wide temperature range typical of temperate climates. It survives winter temperatures down to approximately -20°C (-5°F) and thrives in summer temperatures up to 28°C (82°F). For aquarium or indoor water garden cultivation, maintain temperatures between 18-28°C (64-82°F) for optimal growth.

As a wetland and aquatic plant, marsh pennywort thrives in very high humidity environments and naturally grows in locations with consistently humid conditions such as marshes, bogs, and pond margins. When grown in containers or water gardens, the constant moisture of its growing medium provides the humidity it needs, and it will tolerate any indoor humidity level as long as the soil remains waterlogged.

Marsh pennywort is easily propagated by division of its creeping runners at any time during the growing season, as the stems naturally root at the nodes. Simply separate rooted sections and replant in wet soil or water. It can also be grown from seed by sowing in early spring in a cold frame, though division is quicker and more reliable. Keep divisions constantly moist or in shallow water until established.

Yes, marsh pennywort produces small, inconspicuous greenish-white to purplish-green flowers from June to September (sometimes starting in May). The tiny flowers appear in simple umbels of 3-7 blooms, each cluster measuring about 1-2cm across. While the flowers are not showy or ornamental, they are hermaphrodite and self-fertile, producing seeds that mature from July to October.

Marsh pennywort is primarily an outdoor plant hardy in USDA zones 6-10 and UK zone H5. It thrives in bog gardens, pond margins, water gardens, and as ground cover in consistently wet areas. The plant can grow in full sun to partial shade, tolerates both exposed and sheltered locations, and can be grown submerged in shallow water up to 5cm deep or as a floating plant. Container cultivation is recommended in boggy areas to prevent invasive spreading.

Regular pruning is recommended to control the vigorous spreading of marsh pennywort. Cut back the creeping runners regularly to prevent excessive spread and maintain the desired coverage area. The plant can be very invasive, but it's fairly easy to control by simply pulling out rooted stems or cutting back overgrown sections. Pruning can be done at any time during the growing season without harming the plant.

If growing marsh pennywort in containers, repot when the plant fills its current pot, typically every 1-2 years depending on growth rate. Container cultivation is actually recommended in boggy areas to prevent the plant from spreading invasively into surrounding areas.

Marsh pennywort is generally pest-free and disease-resistant with no serious problems reported. However, it may occasionally be susceptible to mint rust, a fungal disease that can affect plants in the same family. The RHS notes the plant is 'generally pest-free', and Missouri Botanical Garden reports 'No serious pest or disease problems'. Its vigorous growth and aquatic habitat make it less attractive to common garden pests.

The leaves of marsh pennywort are edible when cooked, but the plant has minimal culinary value with an edibility rating of only 1 out of 5. The cooked leaves have a strong carroty taste and cannot be eaten in quantity. While technically edible and non-toxic, marsh pennywort is not commonly used as a food plant and should be considered more of a survival food than a culinary vegetable.

Marsh pennywort has a slight carroty scent when the leaves are crushed or bruised. The fragrance is subtle and not typically noticeable unless the foliage is disturbed. This mild aromatic quality is related to the plant's edibility, as the cooked leaves are described as having a strong carroty taste, indicating similar aromatic compounds.

Marsh pennywort requires minimal cleaning maintenance due to its low-growing, aquatic nature. Growing in wet environments, the leaves naturally stay relatively clean. If grown in a water garden or aquarium, occasional removal of dead or yellowing leaves will help maintain plant health and water quality.

Caring for Marsh Pennywort is a breeze, as it is highly adaptable and forgiving to minor neglect.

Marsh Pennywort’s native range is Europe, including Britain, from Scandanavia south and east to N. Africa, Greece and the Caspian Sea.

Marsh Pennywort is very sensitive to dry soil. To ensure your Penny Rot is thriving and blooming, choose a potting soil that retains moisture. A good soil should still allow for adequate drainage and contain lots of organic matter. Coco coir or sphagnum moss are great soil additives that will help to retain moisture and provide your Pennywort with the nutrients it needs for healthy growth. Make sure to mix these soil additives into the potting soil before planting and water the soil thoroughly. By providing your Marsh Pennywort with a well-draining, moisture-retaining soil, you can help to maximize its growth and keep it blooming.

To ensure optimal growth, the Marsh Pennywort prefers bright indirect light for 6-8 hours each day. Insufficient light can result in slow growth and leaf drop, so it's important to find a well-lit location for this plant. Place it near a window, within a distance of 1 meter (3 feet), to enhance its potential for thriving.

Repotting the Marsh Pennywort should be done either when it has doubled in size or on a yearly basis, whichever occurs sooner. Fresh potting soil with all the required nutrients, refreshed annually, will provide the plant with all the necessary sustenance, making the use of fertilizer unnecessary. Keep in mind that plants receive their energy from the sun, not fertilizer.

Marsh Pennywort is not known to cause harm to humans or pets.

During the cold period, it is common for Marsh Pennywort to go dormant, resulting in a slowdown of growth. To accommodate this, waterings should be spaced out more.