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 in June to August, when five-petaled, yellow flowers develop at the apex of the shoot. Plants die after flowering.
Fruit
The fruit is a 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 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.