Great Mullein (Verbascum thapsus)

Photo: (c) Harry Rose

Family: Scrophulariaceae

Growth Habit: Great Mullein grows to 2.5m. Its height tends to increase in favourable seasons but decrease in poor seasons. It has erect, densely woolly stems. Leaves are grey-green to whitish or yellowish, densely covered with matted layers of white star-shaped hairs giving a woolly appearance and prominently veined on the underside. The young plant is a large rosette. The mature plant has larger leaves at the base, 8 to 50 cm long, 2.5 to 14 cm wide, ovate to elliptical, which graduate to smaller leaves higher up the plant. The soft white hairs which cover the plant gives it the green/ grey appearance.

Type of Plant: An erect biennial herb which can sometimes (though rarely) behave as an annual.

Photo: (c) Harry Rose

Flowers: In late summer, numerous yellow flowers appear up the tall stems. These measure 1.5 to 3cm in diameter 12-18 mm long, and are located on rod-like structures, which taper to a point at the top of the plant.

Fruit/Seed: Great Mullein is a prolific seeder and can produce 250,000 seeds per plant with an expected germination of up to 80%.  The fruit is an ovoid to globose, hairy capsule, 7 to 10 mm long, with a short stalk. Green when young, brown when dry, splitting into 2 valves when mature. Up to 600 seeds per capsule, reddish brown, pitted and ridged, less than 1 mm long, 5 or 6 sided, rod-shaped with one pointed end.

Dispersal: Seed is easily moved by water and soil movement.

Distribution: Great Mullein prefers areas of low fertility eg. rocky outcrops, roadsides or unimproved pastures.

Status: Undeclared in Tasmania.

Weed Impact:

  • The plant is capable of spreading very quickly. Rosettes can cover a large area.
  • Stock will selectively graze other species and avoid Great Mullien. This gives the plant the opportunity to spread if pasture has been overgrazed.
  • This plant is poisonous to stock, but the risk of this occurring is minimal as the animals do not tend to feed on it.

For further information contact the Department of Primary Industry, Parks, Water and Environment, Tasmania.

Control Methods:

  • Cultivation/ grubbing (autumn, winter and spring). Remove entire plant by hand or garden implement.
  • Herbicide (autumn, winter and spring). Herbicides registered in Tasmania include glyphosate and triclopyr.

N.B. Always check the herbicide label before use.