Downy Hop (Humulus pubescens)

Hairy hop Pubescent hop
Silhouette: T. Michael Keesey / License

Humulus pubescens: Morphology and Ecological Significance

Distinguished by the dense, fine hairs covering its leaves and stems, Humulus pubescens thrives as a robust climbing perennial in various ecosystems across the United States. Taxonomists frequently classify this vine as a botanical variety of the widely known common hop. The plant relies on a deep perennial root system to produce rapid herbaceous growth during the spring and summer seasons.

Taxonomy

  • ∟ царство Plantae
  • ∟ division Tracheophytes (Vascular Plants)
  • ∟ subdivision Spermatophytes (Seed plants)
  • ∟ Angiosperms
  • ∟ mesangiosperms (Core angiosperms)
  • ∟ eudicots
  • ∟ Superrosids
  • ∟ rosids
  • ∟ order Rosales
  • ∟ family Cannabaceae (Hemp family)
  • ∟ genus Humulus (Hops)
  • ∟ species Humulus pubescens (Downy Hop)

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Morphology

The most defining morphological characteristic is the dense, velvety pubescence on the lower surfaces of the leaves and along the entire length of the stems. The foliage is opposite, palmately lobed, and possesses a notably coarse, sandpaper-like texture on the upper epidermis.

Key diagnostic features of this taxon include:

  • Stem pubescence: A continuous layer of fine hairs distinguishing it from other related varieties.
  • Resin glands: Present on the papery female cones, emitting a characteristic aromatic scent upon physical disturbance.

Flowering season

Late summer

Jan
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Name
Dec

Applications

The plant serves primarily as an ecological resource rather than a commercially cultivated crop. It acts as an important host plant for various butterfly species, including the comma and question mark butterflies, which rely on its foliage for larval development.

Interesting facts

The dense layer of epidermal hairs on its foliage is scientifically interpreted as an evolutionary adaptation for reducing transpirational water loss and deterring small insect herbivores. Despite its wild nature, genetic introgression occasionally occurs when it hybridizes with cultivated hop varieties.

Geography of distribution

  • United States

Sources

  • Plants of the World Online (POWO)
  • Global Biodiversity Information Facility (GBIF)
  • Tropicos

Technical Information

External Databases: GBIF, POWO, Tropicos

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