The “ren plant,” botanically known as Houttuynia cordata, is a fascinating perennial that presents a unique paradox to gardeners. Its striking appearance and vibrant foliage make it a popular ornamental choice, often seen brightening up gardens with its colorful leaves. However, beneath its appealing facade lies an aggressive nature, as this plant has a strong tendency to spread rapidly. This duality of being both a desirable garden specimen and a potentially invasive species makes understanding and managing Houttuynia cordata particularly important for those considering its cultivation.
Understanding Ren Plant
Houttuynia cordata is a flowering perennial groundcover belonging to the Saururaceae family, often referred to as lizard’s tail. Its common names, such as chameleon plant, fish mint, rainbow plant, and heart leaf, hint at its distinctive features. Native to East Asia, including regions from the Himalayas to Japan, this plant thrives in moist, shady environments.
The plant’s physical attributes include broadly heart-shaped leaves, typically ranging from 4 to 9 cm long and 3 to 8 cm wide. While the species generally has green leaves, the popular ‘Chameleon’ cultivar displays an eye-catching variegation of green, red, pink, yellow, and cream, especially when exposed to ample sunlight. Small, inconspicuous greenish-white flowers emerge on terminal spikes, usually accompanied by four prominent, showy white petal-like bracts.
One of the most notable characteristics of Houttuynia cordata is its distinctive aroma, which can be perceived differently by various individuals. When crushed, the leaves often emit a scent described as cilantro-like, “fishy,” or even citrusy, resembling orange peel, depending on the plant’s chemotype and the individual’s perception. This plant typically grows as a vigorous groundcover, reaching heights of 15 to 60 cm and spreading indefinitely through its extensive rhizomatous root system.
Cultivating Ren Plant
Ideal Growing Conditions
Houttuynia cordata demonstrates adaptability to a range of environmental conditions, making it relatively easy to grow when its preferred settings are met. It thrives in locations offering partial to full shade, though variegated cultivars like ‘Chameleon’ often exhibit more vibrant leaf colors in full sun. The plant is particularly fond of moist to wet soil and can even tolerate shallow standing water, making it suitable for bog gardens or pond margins.
While it prefers consistently moist, humus-rich, and well-draining soil, Houttuynia cordata is tolerant of various soil types, including sandy, loamy, and heavy clay, and can adapt to mildly acidic, neutral, or mildly alkaline pH levels. The plant is quite hardy, generally tolerating temperatures down to about -15°C (USDA Zone 5), though its top growth may die back in colder winters. Despite its hardiness, it does not tolerate drought conditions well, emphasizing the need for consistent moisture.
Planting and Propagation
Planting Houttuynia cordata can be done from nursery starts or by dividing existing plants. When transplanting, ensure the soil is kept consistently moist to aid establishment. Good drainage is still important to prevent root rot, even though the plant prefers wet conditions. Adding organic matter to the soil can help maintain the necessary moisture levels.
Propagation of Houttuynia cordata is notably easy, primarily due to its aggressive rhizomatous growth. The most common and effective method is division, which can be performed in spring or early summer. Simply dig up a portion of the plant, separate the rhizomes, ensuring each new section has roots and at least one growing point, and then replant them. Stem cuttings can also be rooted in water or moist potting mix, and while less common, propagation from seed is also possible.
Managing Ren Plant’s Spread
Understanding its Invasive Nature
Houttuynia cordata is recognized for its aggressive, invasive tendencies in many non-native regions. Its primary method of spread is through a vigorous system of underground rhizomes, which can extend indefinitely and rapidly colonize new areas. These rhizomes are particularly fragile and break apart easily, with each small fragment capable of resprouting and forming a new plant.
This plant’s ability to outcompete other species stems from its dense mat-forming growth habit and rapid reproductive rate, both sexually through seeds and asexually via rhizomes. Once established, Houttuynia cordata can be very difficult to remove, as even small pieces of root left in the soil can lead to regrowth. Early intervention and proactive containment are therefore important to prevent it from overwhelming garden spaces or escaping into natural habitats.
Physical Removal Techniques
Manual removal of Houttuynia cordata requires persistence due to its tenacious rhizomatous network. Digging out the plant is a common method, but it is important to remove every piece of rhizome, as any left behind can regrow. This often means sifting through the soil carefully to ensure all fragments are collected. Repeated pulling of new shoots as they emerge can also weaken the plant over time by depleting its energy reserves.
Another physical technique involves smothering the plant by covering the infested area with opaque tarps or thick layers of cardboard. This blocks sunlight, which is necessary for the plant’s growth, eventually starving the rhizomes. This method can take several months to a full growing season to be effective. Consistent monitoring and follow-up are necessary to address any regrowth from missed fragments or dormant seeds.
Chemical Control Considerations
Chemical control using herbicides is often considered a last resort for Houttuynia cordata due to its resilience and the potential impact on surrounding plants. Herbicides containing glyphosate are sometimes recommended for severe infestations. For effective application, it is often advised to cut back the plant’s foliage in early summer, allowing it to regrow new, tender leaves before applying the herbicide.
Applying glyphosate directly to cut stems can also be an option for a more targeted approach. However, caution is necessary as glyphosate can harm desirable plants upon contact. Always follow product label instructions precisely, including recommended concentrations and safety precautions, to minimize environmental impact and ensure personal safety. Repeated applications over several growing seasons may be necessary for complete eradication.
Containment and Prevention
Preventing the aggressive spread of Houttuynia cordata is often more manageable than attempting to eradicate it once established. One effective strategy is to plant it in containers, which physically restrict its rhizomes from spreading into the surrounding soil. For in-ground planting, installing sturdy root barriers made of metal or thick plastic can help confine the plant to a designated area. These barriers should extend deep enough into the soil to prevent rhizomes from growing underneath.
Diligent monitoring is also important, regularly checking for any shoots emerging outside the intended planting zone and promptly removing them. When pruning or clearing plant material, responsible disposal is necessary to avoid accidental propagation. Do not compost Houttuynia cordata trimmings unless the compost pile reaches consistently high temperatures, as viable rhizome fragments could survive and spread. Instead, dispose of plant material in sealed bags or by incineration where permitted.
Uses of Ren Plant
Culinary Applications
Houttuynia cordata is widely appreciated in various Asian cuisines, where its unique flavor profile adds a distinctive touch to dishes. Known as “fish mint” in many regions, its leaves are frequently used as an herb in salads, soups, and stir-fries. The flavor can be described as a combination of cilantro, fishy notes, and a peppery or citrusy taste, depending on the cultivar and individual palate.
In northeastern India, the leaves are commonly incorporated into salads and salsas, or cooked with other vegetables. The tender roots can also be ground into chutneys, often paired with dry meat or fish and chilies. In parts of China, particularly Guizhou, the roots (known as zhé’ěrgēn) are a staple, often fried with cured pork belly or used as a condiment for noodles.
Traditional Medicinal Uses
Beyond its culinary uses, Houttuynia cordata has a long history of application in traditional medicine systems across East Asia. It is believed to possess various properties, including anti-inflammatory, antiviral, antibacterial, and antioxidant effects. Traditionally, decoctions made from the plant have been used internally to address ailments such as coughs, dysentery, fevers, and to strengthen the immune system.
Externally, it has been applied in treatments for snake bites and skin disorders. While traditional uses are extensive, it is important to understand that these applications are based on historical practices and not all are supported by modern clinical research. For any health concerns, consulting a healthcare professional is always recommended.
Ornamental and Groundcover Use
Despite its invasive potential, Houttuynia cordata is intentionally cultivated in gardens for its ornamental appeal, particularly its colorful variegated forms. The ‘Chameleon’ cultivar, with its striking blend of green, red, pink, and yellow foliage, is a popular choice for adding visual interest. Its low-growing, spreading habit makes it an effective groundcover in areas where its spread can be controlled.
It is often used in moist, shady areas of the garden, such as bog gardens, pond margins, or woodland settings, where its preference for wet conditions can be met. When grown as an ornamental, it is generally recommended to use containers or root barriers to manage its aggressive spreading nature. This allows gardeners to enjoy its beauty without it overwhelming other plants in the landscape.