Persicaria capitata is a medicinal plant known via a range of common names which include Pink Knotweed, Japanese Knotweed, Himalayan Smartweed and Pink Bubble Persicaria. A member of the Polygonaceae family, this plant used to be known botanically as Polygonum capitatum but now has been reclassified into a new genus, Persicaria.
A native of Asia, this plant has naturalised in various parts of the world and has become an invasive weed in areas where the climate permits. It is an herbaceous plant that adopts a prostrate growth habit, meaning it creeps near the surface of the plant. Owing to this growth habit, Persicaria capitata is often grown as a groundcover plant.
A candidate for medicinal gardens, it is a highly ornamental plant suited for planting in the foreground in a landscape. For example, it can cleverly be grown between some rocks. The leaves of Persicaria capitata are green in colour and the chevron that adorns each leaf becomes more obvious under direct sunlight. The reddish stems contrast against strongly the foliage. Flowers of this plant are produced freely in the form of small pink globes that are held well above the foliage. This plant emits a strong odour when parts of it are crushed.
Persicaria capitata is a perennial plant in Singapore which prefers to be grown under direct sunlight and a moist, well-draining location. It seems to be able to grow in poor, clayey soils and can be drought-tolerant when established. Under optimal growing conditions, it is able to form a dense mat of foliage that hugs the ground. It is relatively pest- and disease-free under local conditions and can be easy to propagate it via stem-cuttings. Note that it is important to plant Persicaria capitata in a weed-free area as it has been noted that grassy weeds can still grow through a dense mat of this plant and eradication of these unsightly weeds can be very difficult to perform.
Persicaria capitata is used in Traditional Chinese Medicine where its aerial parts are used to brew a tea which is consumed for the treatment of a range of urological disorders, such as kidney stones and urinary tract infections. An in-vitro study reported that traditional use of this plant for the treatment of urinary tract infections can be attributed to the presence of anti-bacterial and anti-inflammatory agents found in the plant. Persicaria capitata has also been found to contain antioxidants.