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Redshank Revelation: Growing, Caring, and Using Polygonum orientale

The Polygonum orientale is an annual herbaceous plant of the buckwheat family, Polygonaceae. Boasting a robust and upright stem that can reach up to 2 meters in height, its leaves are broad-ovate, broad-elliptical, or ovate-lanceolate in shape, tapering to a pointed tip, with a rounded or nearly heart-shaped base. Both surfaces are densely covered with […]

The Polygonum orientale is an annual herbaceous plant of the buckwheat family, Polygonaceae.

Boasting a robust and upright stem that can reach up to 2 meters in height, its leaves are broad-ovate, broad-elliptical, or ovate-lanceolate in shape, tapering to a pointed tip, with a rounded or nearly heart-shaped base.

Both surfaces are densely covered with short soft hairs, with longer soft hairs along the veins; the petioles are also covered with long soft hairs. The stipules form a tubular sheath of membranous texture.

The plant bears spike-like, dense, and somewhat drooping panicles at the tips or in the leaf axils, with broadly funnel-shaped, green, herbaceous bracts. The flowers are pale red or white, with elliptical tepals and a distinct floral disc.

Polygonum orientale

The nearly round achene fruit matures between August and October, following a blooming period from June to September.

The Oriental Persicaria is favored for its rapid growth, substantial height, lush green leaves, and dense clusters of bright red flowers, coupled with its strong adaptability, making it an excellent choice for ornamental purposes.

Its fruit is used in traditional medicine under the name “Shui Hong Hua Zi” and is believed to invigorate the blood, relieve pain, reduce stagnation, and promote urination.

I. Morphological Characteristics

Redshank is an annual herbaceous plant. Its stem is erect, robust, and grows to a height of 1-2 meters, with many branches at the upper part, densely covered with long, soft hairs.

Polygonum orientale

The leaves are broad ovate, wide elliptical, or ovate-lanceolate, measuring 10-20 centimeters in length and 5-12 centimeters in width.

They taper to a point at the tip, have a rounded or nearly heart-shaped base that extends slightly downward, and feature smooth edges with dense marginal hairs.

Both surfaces are covered with short, soft hairs, while the veins are densely populated with long, soft hairs. The petioles are 2-10 centimeters long, also bearing long, soft hairs.

The stipules form a tubular sheath, membranous, 1-2 centimeters long, covered with long, soft hairs, and have long marginal hairs, usually with green, herbaceous wings along the top.

The inflorescence is a dense, spike-like cluster that appears terminally or axillary, measuring 3-7 centimeters in length, with flowers that are tightly packed and slightly drooping, often grouped together to form a conical shape.

The bracts are wide, funnel-shaped, 3-5 millimeters long, green, herbaceous, and covered with short, soft hairs, with long marginal hairs, each containing 3-5 flowers.

The pedicels are longer than the bracts; the perianth is deeply 5-lobed, pale red or white; the perianth segments are elliptical, 3-4 millimeters long; there are 7 stamens, longer than the perianth; the disk is prominent; the styles are 2, fused at the middle and lower parts, longer than the perianth, with capitate stigmas.

The achene is nearly round, biconvex, with a diameter of 3-3.5 millimeters, dark brown, and glossy, enclosed within the persistent perianth. The flowering period is from June to September, with the fruiting period from August to October.

II. Growth Environment

Found throughout China except for Tibet, this plant also grows in Korea, Japan, Russia, the Philippines, India, Europe, and Oceania, whether in the wild or cultivated. It thrives in moist areas beside ditches and roads near villages, at altitudes ranging from 30 to 2,700 meters.

Preferring warm and humid conditions, it requires ample sunlight. The plant is highly adaptable, with no strict soil requirements, and thrives in various soil types.

It favors fertile, moist, and well-drained soil but can also tolerate poor conditions. Red knotweed loves water yet withstands drought, typically growing in valleys, along roadsides, on ridges between fields, and on grasslands and riverbanks, often forming large clusters.

Remarkably resilient, red knotweed is virtually free from diseases and pests and can grow well with minimal care.

III. Growth and Propagation

Redshank propagates through its seeds.

Seed collection takes place annually between September and October, coinciding with the maturation of redshank seeds. It is essential to harvest the seeds promptly.

After removing the husks, the seeds should be dried in the shade and then stored in a sealed and dry location. Sowing begins in March for spring seedling cultivation. Before sowing, the soil should be deeply plowed and leveled.

Holes should be made at a row and plant spacing of 30-35 centimeters, with a depth of about 7 centimeters. Approximately 10 seeds are sown per hole, with a sowing rate of 9-15 kg per hectare, and covered with 2-3 centimeters of fine soil.

After sowing, apply a mixture of human and animal liquid manure and cover with a layer of wood ash or fine soil about 1 centimeter thick.

Subsequently, water spray should be applied once or twice a week for thorough permeation. After seedlings emerge, thin them out in a timely manner to maintain a spacing of about 30 centimeters between plants.

IV. Pest and Disease Control

Red knotweed rarely suffers from insect damage, but it does occasionally fall prey to brown spot disease, which can hinder its growth.

Brown spot disease causes lesions on the red knotweed leaves. These spots appear on both sides of the leaves, starting as small yellow-brown dots that are circular or nearly so, sometimes irregular, measuring 3-6 millimeters in diameter.

A single leaf may have several dozen such spots, which can gradually expand to form lesions 1-2 centimeters across, with a pale brown center and distinct concentric rings of varying shades.

In severe cases, the lesions can reach 2-3 centimeters in diameter. The affected areas may exhibit a gray-black moldy substance, which is the conidiophores and conidia of the pathogen.

The pathogen, known as Septoria polygonorum, is a fungus belonging to the subdivision Ascomycotina. This fungus infects both sides of the leaf and thrives at temperatures between 27-30°C, ceasing development above 37°C or below 5°C.

The optimal temperature for conidia germination is 26-31°C, with an ideal relative humidity of 98%-100%.

Control Methods

  • Remove infected plant debris, dry grass, and pruned remnants in late autumn or early winter to reduce the source of infection.
  • Before or during hot and humid weather, apply less or no nitrogen fertilizer, maintain adequate levels of phosphorus and potassium fertilizers, and avoid flood or furrow irrigation, especially watering in the evening.
  • At the initial onset of the disease, when dry spots appear, fungicides such as methotrexate or tebuconazole may be used for control. In severe cases, spray a 1500x dilution of 50% benomyl wettable powder or use Amistar for treatment.

V. Primary Value

Ornamental Use

Red knotweed is an excellent herbaceous plant for greening and beautifying gardens. Its stems, leaves, and flowers are suited for ornamental purposes and can be planted in courtyards, along walls, or beside ditches to embellish spaces where people seldom tread.

Indoor hydroponic cultivation of red knotweed is also quite simple. Cut a segment of the branch, place it in a vase with water, and within a few days, it will root and grow in the water.

Positioned on a windowsill or computer desk, it not only increases indoor humidity but also offers ornamental appeal.

Medicinal Use

Indications: Dispels wind and eliminates dampness; clears heat and detoxifies; promotes blood circulation; prevents malaria.

Primarily used for rheumatic pain; dysentery; diarrhea; convulsions associated with cholera; edema; beriberi; carbuncles, boils, and sores; snake and insect bites; pediatric indigestion and hernia; injuries from falls and blows; and malaria.

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Founder of FlowersLib

Peggie was once a high school mathematics teacher, but she set aside her chalkboard and textbooks to follow her lifelong passion for flowers. After years of dedication and learning, she not only established a thriving flower shop but also founded this blog, “Flowers Library”. If you have any questions or wish to learn more about flowers, feel free to contact Peggie.

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