Japanese hops are an invasive species.
- Japanese hops are found in sunny riparian areas, grasslands, hayfields and roadsides.
- This vine aggressively climbs over trees and larger vegetation, creating dense patches and choking out other vegetation.
- The tiny hairs on the stem can irritate bare skin.
Japanese hops should be reported. The Minnesota Department of Natural Resources provides detailed recommendations for reporting invasive species.
How to identify Japanese hops
- Japanese hops (Humulus japonicus) is an annual vine with palmately arranged leaves.
- Can grow up to 35 feet in a single growing season.
- Stems and leaves have hooked hairs.
- Stems are covered with downward-pointing prickles.
Opposite, toothed leaves are divided into five to seven lobes; two to five inches long.
- Bracts occur where the leaf petioles attach to the stem.
- There are separate male and female plants.
- Flowers occur in clusters, are green in color and don’t have petals.
- Male flowers are upright while female flower clusters droop down.
- Blooms mid to late summer.
- Single flattened seeds from each female flower.
- Each inflorescence produces several seeds that mature in September.
- Plant produces yellow-brown achenes.
- Seeds remain viable in soil for up to three years.
- Whole hops can float and travel in the current for dispersal.
- Younger plants have small white roots that quickly establish into a fibrous mass.
- Roots easily break off when pulled and quickly resprout another vine.
Reviewed in 2019