Houttuynia cordata (heart-leaved houttuynia)
Heart-leaved houttuynia is a creeping herb with fleshy stems and a scent that has been described as lemon, sandalwood, coriander or raw fish.
About this species
Houttuynia cordata was first described by the Swedish naturalist Carl Peter Thunberg in his Flora Japonica in 1784 from material collected in Japan. It is also common in the wetter and warmer parts of China, where it is valued for its many uses. For example, the shoots are eaten as a vegetable and aerial parts are used in traditional Chinese medicine (TCM). There are two distinct chemotypes: the Japanese type has an orange scent, whereas the Chinese type has a smell resembling coriander.
Geography & Distribution
Houttuynia cordata has a wide native range, from Nepal and India in the west, through China and Indochina to Japan in the east, and south via Thailand to the mountains of Java (Indonesia). It is found from near sea-level to an elevation of 2,500 m. It has been introduced to Australia, New Zealand, some Pacific islands and North America and is frequently considered a weed.
Houttuynia cordata is a creeping herb 30–60 cm high, with thin, spreading rhizomes. The stems are green or sometimes purplish red, and either smooth or pubescent on the nodes. The lower parts of the leaf stalks form a sheath round the stem. The leaves are usually heart-shaped, 4–10 cm long and 2.5–6.0 cm wide, and purple underneath. The flowers are small, crowded into a short spike around 2 cm long, with four white, petal-like bracts at the base. The stamens usually degenerate, and the fruits are apomictic, i.e. they develop seeds without being fertilized.
Apart from the wild green-leaved form, there are cultivars with red, pink, golden and white leaves (such as ‘Chameleon’, ‘Flame’, ‘Joker’s Gold’, ‘Sunshine’ and the ‘Variegata group’), and one with extra petal-like bracts (‘Flore Pleno’).
Illustration from Curtis's Botanical Magazine
A hand-coloured engraving of Houttuynia cordata by W.J. Hooker (1827) taken from Curtis’s Botanical Magazine (Image: RBG Kew)
Curtis’s Botanical Magazine (Editor: Martyn Rix) provides an international forum of particular interest to botanists and horticulturists, plant ecologists and those with a special interest in botanical illustration.
Now well over two hundred years old, the Magazine is the longest running botanical periodical featuring colour illustrations of plants. Each four-part volume contains 24 plant portraits reproduced from watercolour originals by leading international botanical artists. Detailed but accessible articles combine horticultural and botanical information, history, conservation and economic uses of the plants described.
Published for the Royal Botanic Gardens, Kew by Wiley-Blackwell Publishing.
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Threats & Conservation
This species is widespread and not threatened. There are concerns that it could become invasive in the future because it spreads quickly and is difficult to control once introduced into a favourable area. It therefore may pose a potential threat to natural habitats.
Heart-leaved houttuynia is grown as an ornamental and groundcover. In many parts of its range it is grown as a salad crop or as a medicinal herb. The tender shoots and leaves are eaten raw or cooked. In Nepal, juice from the roots is used for treating indigestion and applied to the skin to treat wounds and skin diseases. The aerial parts are used medicinally in both China and Japan. In traditional Chinese medicine (TCM), they are used to treat respiratory tract infections, inflammation of the urinary tract and carbuncles and sores.
Millennium Seed Bank: Seed storage
The Millennium Seed Bank partnership aims to save plant life worldwide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in Kew's seed bank vault at Wakehurst.
Description of seeds: Average 1,000 seed weight = 0.04 g.
Number of seed collections stored in the Millennium Seed Bank: Two.
This species at Kew
Pressed and dried specimens of Houttuynia cordata are held in Kew’s Herbarium, where they are available to researchers from around the world, by appointment. The details of one of these specimens, including an image, can be seen online in the Herbarium Catalogue.
Identifying plants in products
Since the early 1990s there has been a large increase in the diversity of plant-based products traded worldwide for making cosmetics, herbal medicines (especially traditional Chinese medicines), functional foods, potpourri, colouring agents and pet products.
Kew is investigating these using a range of morphological as well as chemical and DNA fingerprinting methods to identify species of plants being traded and to study whether plant-derived products contain the appropriate range of compounds associated with their proposed use.
Over 1,000 species and over 1,500 plant extracts have been studied so far. Although in most cases the correct species has been traded, there have been a few incidents when incorrect species or poor-quality substitutes have been sold. Other issues relate to the over-exploitation of some species, especially those that are wild collected and where there is a need to develop sustainable harvesting practises to avoid adulterants or poor-quality material entering the trade.
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