Humulus is a genus with – depending on species boundaries – three to up to ten species from the northern hemisphere. One species, Humulus lupulus L., is a common native plant in Belgium. It is also locally cultivated (hop) for flavouring beer or as an ornamental. A second species, Humulus japonicus, is cultivated for ornament and occurs as an invasive escape in many parts of the world (including parts of southern Europe).
1 Annual. Abaxial side of leaf blades stiffly hairy, especially on the nerves. Petioles usually longer than the blades, the lowermost blades (5-)7(-9) lobed. Anthers non-glandular === Humulus japonicus
Perennial. Abaxial side of leaf blades glabrous or softly pubescent. Petioles usually shorter than the blades, the lowermost blades 3-5 lobed. Anthers glandular (native) === H. lupulus
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