Appearance
Verbascum thapsus is a biennial forb native to Eurasia and Africa. Plants are unbranched and can grow to more than 6.6 ft. (2 m) tall.

Foliage
First year plants develop as a basal rosette of felt-like leaves. Basal leaves are 4-12 in. (10.2-30.5 cm) long, 1-5 in. (2.5-12.7 cm) wide, and covered with woolly hairs. Cauline (stem) leaves are decurrently alternate and decrease in size towards the apex.

Flowers
The plant bolts in the second year. Flowering occurs from June to August when five-petaled, yellow flowers develop at the apex of the shoot. Plants die after flowering.

Fruit
The fruit is an ovoid capsule that splits, releasing 100,000 to 180,000 seeds from the parent plant, that germinate in water.

Ecological Threat
Once established it grows quickly to form a dense ground cover. It can overtake and displace native species. At the high densities, it appears to prevent the establishment of native herbs and grasses following fires or other disturbances. Verbascum thapsus occurs in areas with an average annual precipitation of 20-60 in. (0.5-1.5 m) and a 140-day growing season. It prefers well-drained soils with pH 6.5 to 7.8. It prefers dry sandy soils but can grow in chalk and limestone. It can be found in neglected meadows, forest openings, pastures, fence rows, roadsides, and industrial areas.

Resources

• Weeds Gone Wild: Alien Plant Invaders of Natural Areas - Plant Conservation Alliance
• Element Stewardship Abstract - The Nature Conservancy
• Weed of the Week - USDA Forest Service

Selected Images

Maps

Invasive Listing Sources

• Alberta Weed Control Act
• California Invasive Plant Council
• City of Ann Arbor Michigan Parks and Recreation
• Colorado Noxious Weeds
• Georgia Exotic Pest Plant Council - Category 4
• Hawaii Noxious Weeds
• Hoffman, R. & K. Kearns, Eds. 1997. Wisconsin manual of control recommendations for ecologically invasive plants. Wisconsin Dept. Natural Resources, Bureau of Endangered Resources. Madison, Wisconsin. 102pp.
• Invasive Plant Species of West Virginia
• Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
• John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
• Kentucky Exotic Pest Plant Council - Significant Threat
• National Park Service, Mid-Atlantic Exotic Plant Management Team Invasive Plant List
• Native Plant Society of Oregon, 2008
• Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
• Pacific Northwest Exotic Pest Plant Council, 1998
• WeedUS - Database of Plants Invading Natural Areas in the United States
• West Virginia Invasive Species Strategic Plan and Volunteer Guidelines 2014
• West Virginia Native Plant Society, Flora West Virginia Project, and West Virginia Curatorial Database System, September 3, 1999
• Wyoming Noxious Weeds

References