Humulus japonicus, known as wild hop or Japanese hop, synonym H. scandens, is an ornamental plant in the Cannabaceae family. Originally found in temperate parts of Asia (China, Japan, Korea, Taiwan and Russia) and the tropical environment of Vietnam, it was imported to North America in the 1800s for use in an Asian tonic and as an ornamental plant. Since its arrival in North America, it has spread widely. It can be found throughout the Northeastern U.S. and eastern Canada. It is considered an invasive species in North America. The composition and chemistry of its oils differ from those of its relative the common hop, Humulus lupulus. As a result, the Japanese hop is not used in the production of beer.
Well-developed leaves with 5-9 lobes; abaxial surfaces of leaves pubescent, but not densely so; infructescence rarely longer than 2 cm, with bracts and bracteoles less than 1 cm long, and notable spinulose-ciliate Inflorescences: staminate inflorescences erect, 15–25 cm, flower anthers without glands; pistillate inflorescences spikes, conelike, ovoid; bracteole ovate-orbiculate, 7–10 mm, pilose, margins densely ciliate-hairy. Infructescences pendulous, green, conelike, ovoid to oblong, (1-)1.5-3(-4) cm; bracteoles without yellow glands.
Seeds germinate in early spring, but plants may continue to emerge if conditions are favorable. Seeds can be dispersed by number of agents including humans, animals, machines, and flood waters.
Distribution and habitat
Humulus japonicus originates in temperate regions of Asia and the Tropics of Vietnam, but has become an invasive species in North America since it was imported in the 1800s. The plant has been immensely successful in North America, where it has an enormous range. It can be found throughout eastern Canada and the eastern half of the United States. In the United States Humulus japonicus has a lateral range from North Dakota to Maine and a vertical range from Minnesota to Georgia. Japanese hops grow well given plentiful sunlight, moisture, and nutrient rich soil, and are most commonly found along stream banks and floodplains. Japanese hops do not grow as well in shaded areas and drier soils. In milder climates, it can survive the winter.
The Japanese hop can adapt well to new environments. Its range and distribution in North America prove that it can thrive in a wide range of environments, from the southern regions of the U.S. to the far reaches of northern of Canada. It can grow and cover any area quickly. Thousands of hop plants can grow in one acre, and they can blanket a majority of the local vegetation. The vines grow rapidly during the summer, climbing up and over everything in their path, and can form dense mats several feet deep, blocking light to plants underneath.
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- "Humulus japonicus in Flora of North America @ efloras.org". www.efloras.org. Retrieved 2015-12-07.
- "Plants Profile for Humulus japonicus (Japanese hop)". plants.usda.gov. Retrieved 2015-12-07.
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