Geum japonicum aka Asian Herb Bennet

Geum japonicum is generally considered easy to grow. Plants For A Future and Useful Temperate Plants both describe it as easily grown in moderately good, well-drained garden soil, with the only notable horticultural quirk being that it hybridizes freely with other Geum species when planted nearby. No special equipment or technical skill is required beyond basic perennial care.

Mature plants reach roughly 0.6 m (2 ft) tall, growing from a basal rosette of leaves typical of the genus Geum. Flower stalks are wiry and emerge above the foliage in early summer.

Geum japonicum prefers consistently moist soil rather than dry conditions. Plants For A Future lists 'moist soil' as the preference, and Useful Temperate Plants emphasizes well-drained but organic-rich soil that retains some moisture; it is not drought-tolerant and not aquatic.

The species tolerates light (sandy), medium (loamy) and heavy (clay) soils, ideally well-drained and enriched with organic matter. Soil pH from mildly acid through neutral to mildly alkaline is acceptable, making it adaptable across most garden soils.

Geum japonicum is hardy across roughly USDA zones 6-9 (UK zone 7). At the genus level, Geum species remain evergreen except where winter temperatures fall below about −18 °C (0 °F), which corresponds to the cold limit of the species' useful range.

Plants typically remain evergreen through mild winters and only die back where temperatures drop below about −18 °C (0 °F). Flowering occurs in June and July with seed ripening in July and August, and clumps benefit from division every three to four years in spring or autumn to maintain vigor.

Geum japonicum produces yellow flowers on wiry stalks during June and July, with seed ripening from July into August. The genus Geum overall is known for flowers in shades of white, red, yellow and orange in midsummer.

A recognized infraspecific taxon is Geum japonicum var. chinense F.Bolle. The species also has several historical synonyms including Geum iyoanum Koidz., Geum sieboldii Scheutz, and Geum japonicum f. iyoanum (Koidz.) H.Ikeda.

The species is suited to outdoor garden cultivation, where it is easily grown in moderately good, well-drained soil enriched with organic matter. It accepts either semi-shade or full sun and is hardy through roughly USDA zones 6-9. Note that it hybridizes freely with other Geum species, so seed-grown offspring may not come true if other Geum varieties are present.

Flowers are insect-pollinated (entomophilous). At the genus level, Geum species also serve as larval food for some Lepidoptera.

The leaves of Geum japonicum are recorded as edible, although Plants For A Future gives the species a modest edibility rating of 1 out of 5 and provides no specific culinary preparations beyond noting that the plant is harvested from the wild in Japan for local use.

Geum japonicum has a long history in East Asian traditional medicine. The whole plant is regarded as diuretic and astringent and has been cooked with other foods to treat coughs and haemoptysis, while the roots are applied externally as a poultice for boils and ulcers. Modern pharmacological studies have isolated polyphenols, ellagic acid and a series of tannins (gejaponin A-G) and have reported cardioprotective, anti-platelet, neuroprotective and antidepressant-like activities in laboratory models, though clinical evidence remains limited.

No notable non-medicinal, non-culinary uses are recorded. Plants For A Future rates the species 0 out of 5 for 'other uses'.

Asian Herb Bennet’s native range is N. America, E. Asia.

To ensure optimal growth, the Asian Herb Bennet prefers bright diffused 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.

Asian Herb Bennet is not known to cause harm to humans or pets.