Humulus japonicus or Japanese hop is a vine from the hemp family, evergreen in tropical and sub-tropical regions but grown as annuals in colder climates.
It is a strong grower that can grow to 5-8 m high, provided it has a good support. Without support, it grows as ground cover. It is perfect to cover a wall or fence.
In warm to temperate regions, the species is invasive and can cover large areas quickly and smother the local flora.
The leaves are dark green, 5-6 cm long, 5-7-lobed. The leaves are covered with short stiff hairs on the top and short prickly hairs on the underside. The leaf stalk is as long or slightly shorter than the leaf and covered with short stiff and prickly hairs. The stem is green to purple and also covered with hairs.
The plant is dioecious, male flowers are 5 mm in diameter and female flowers 15-20 mm in diameter, both are light green. The female flowers grows in a short spike that hangs over with time. The flowering takes place from the mid-summer to autumn and lasts about 2 months. Pollination and distribution of the seeds is done by the wind.
The flowers attract bees and butterflies. Please note that the pollen is an allergen.
Humulus: origin uncertain, it could be derived from the German humela or from humus (soil)
Japonicus: new Latin derived from japonia (from Japan, Japanese)
Moist soil, in open plains, on the edge of rivers, lakes and roads
USDA zones 4-8 (the plant dies but growth resumes next spring)
Moist, deep, humus-rich, acidic, neutral or alkaline, tolerates lime soil
Sun, partial shade
In pot, fertilize weekly with universal liquid fertilizer. In the garden, in spring with solid fertilizer.
May be cut down to soil level at the first frost
- sow in early spring, indoors or under glass have get an early start
- sow in a light and moist mix, at 0,5 cm depth
- 18-22 °C
- germination: 25-30 days