Europe and Asia
Common mullein, also known
as wooly mullein, is an erect herb. First year mullein plants are low-growing
rosettes of bluish gray-green, feltlike leaves that range from 4-12 inches
in length and 1-5 inches in width. Mature flowering plants are produced
the second year, and grow to 5 to 10 feet in height, including the conspicuous
flowering stalk. The five-petaled yellow flowers are arranged in a
leafy spike and bloom a few at a time from June-August. Leaves alternate
along the flowering stalks and are much larger toward the base of the plant. The
tiny seeds are pitted and rough with wavy ridges and deep grooves and can
germinate after lying dormant in the soil for several decades.
Common mullein threatens
natural meadows and forest openings, where it adapts easily to a wide variety
of site conditions. Once established, it grows more vigorously than
many native herbs and shrubs, and its growth can overtake a site in fairly
short order. Common mullein is a prolific seeder and its seeds last
a very long time in the soil. An established population of common mullein
can be extremely difficult to eradicate.
DISTRIBUTION IN THE UNITED STATES
mullein was first introduced into the U.S.
in the mid-1700's, where it was used as a piscicide, or fish poison,
in Virginia. It quickly spread throughout the U.S. and is well established
throughout the eastern states. Records show that it was first described
in Michigan in 1839 and on the Pacific coast in 1876, probably due to multiple
introductions as a medicinal herb.
HABITAT IN THE UNITED STATES
mullein can be found where mean annual precipitation is greater than 3-6
inches and the growing season lasts for a minimum of 140 days. Intolerant
of shade, mullein will grow in almost any open area including natural meadows
and forest openings as well as neglected pastures, road cuts, industrial
areas. Common mullein prefers, but is not limited to, dry sandy soils.
mullein is a monocarpic perennial (i.e., takes two or more years to flower
and die). Brought over from Europe by settlers, it was used as a medicinal
herb, as a remedy for coughs and diarrhea and a respiratory stimulant for
the lungs when smoked. A methanol extract from common mullein has been
used as an insecticide for mosquito larvae.
BIOLOGY & SPREAD
During the first
summer after germination mullein produces a tap root and a rosette of leaves. During
this vegetative stage, the rosette increases in size during the growing season
until low temperatures arrest growth sometime during the autumn and winter. Beginning
the next spring, second year plants bolt into maturity, flower, produce seed
during the summer, and then die, completing the plant’s normal life cycle. Flowers
mature from the base to the tip of the stalk. The length of the flowering
period is a function of stalk height; longer stalks can continue to flower
into early October. It is estimated that a single plant can produce
100,000-180,000 seeds which may remain viable for more than 100 years. The
seeds are dispersed mechanically near the parent plant during the autumn
and winter. Seeds at or near the surface are more likely to germinate.
Although common mullein
can be very difficult to eradicate, there are a variety of management methods
available, depending on the particular situation. Because mullein seedling
emergence is dependent on the presence of bare ground, sowing
sites with early successional native grasses or other plants may decrease
seed germination and the chance of successful emergence of mullein seedlings.
Manual and Mechanical
Mullein plants are
easily hand pulled on loose soils due to relatively shallow tap roots. This
is an extremely effective method of reducing populations and seed productivity,
is pulled before seed set. If blooms or seed capsules are present, reproductive
structures should be removed, bagged, and properly disposed of in a sanitary
landfill. Care should be taken, however, to minimize soil disturbance
since loose soil will facilitate mullein seed germination.
There are two insects that
have possible biological control implications for mullein. A European
curculionid weevil (Gymnaetron
tetrum), determined by the U.S. Department of Agriculture to be specific
to mullein, has been introduced to North America. The weevil larvae
matures in the seed capsules and can destroy up to 50% of the seeds. Another
agent, the mullein moth (Cucullia verbasci) has been tested in the
U.S. and is considered to be a relatively safe control agent because of its
consistent feeding and development on mullein species. Although tests
showed limited feeding on other native species, the larvae did not survive
significantly longer than those individuals tested in the absence of food.
Release of biological
controls into natural environments is always experimental and should be
entered into only after full and careful consideration of potential non-target
species impacts. Once released into nature, biological control agents
are difficult if not impossible to control.
For situations where hand-pulling
of plants is not practical or safe, for example, on very steep slopes where
is dangerous or would cause significant soil disturbance, herbicidal control
is an effective option. Apply a 2% solution of glyphosate (e.g., Roundup®)
or triclopyr (Garlon) and water plus a non-ionic surfactant, using a tank
or backpack sprayer to thoroughly cover all leaves. Do not apply so
heavily that the herbicide drips off the leaf surface. Use caution
as glyphosate is a non-selective herbicide that may kill desirable plants
even if partially contacted by spray. Triclopyr is selective to broadleaf
plants and is a better choice if native or other desirable grasses are present. For
some sites, applications can be made during the early spring when most other
non-target vegetation is dormant. Refer to the pesticide manufacturers'
label for specific information and restrictions regarding herbicide use.
USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS.
NOTICE: MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.
For more information on
the management of Common Mullein, please contact:
- Kris Johnson, Great Smoky Mountains
National Park, Gatlinburg, TN
SUGGESTED ALTERNATIVE PLANTS
a popular ornamental, there are many excellent native plant alternatives for
mullein that thrive in full sun and sandy soils. In the eastern U.S., common
milkweed (Asclepias syriaca), butterflyweed (Asclepias
tuberosa), joe-pye weed (Eupatorium dubium), black-eyed Susan
(Rudbeckia fulgida), and Ironweed (Vernonia noveboracensis), are
just a few of the many selections. You may wish to contact your local native
plant society for further suggestions.
Tom Remaley, Great Smoky Mountains National
Park, Gatlinburg, TN
Jil M. Swearingen, National Park Service,
National Park Service
Forest & Kim Starr, US Geological Survey, HI
Baskin, J.M. and C.C. Baskin. Seasonal
changes in germination responses of buried seeds of Verbascum thapsus and V.
blattaria and ecological implications. Can. J. Bot. 59: 1769-1775;
Haragan, Patricia D. Weeds of Kentucky and Adjacent
States. Lexington, KY: The Univ. Press of Kentucky; 1991: 136-7.
Martin, Alexander C. 1987. A Golden
Guide: Weeds. Golden Press, New York, p. 106.
Maw, M.G. Cucullia verbasci an Agent for
the Biological Control of Common Mullein (Verbascum thapsus). Weed
Sci. 28(1): 27-30; 1980.
Radford, A. E., H. E. Ahles, and C. R. Bell. Manual
of Vascular Flora of the Carolinas. Chapel Hill, NC: Univ. of North
Carolina Press; 1968.
Semenza, R. J., J. A. Young, and R. A. Evans. Influence
of Light and Temperature on the Germination and Seedbed Ecology of
Common Mullein (Verbascum thapsus). Weed Sci. 26(6): 577-81;
Swearingen, J. 2009. WeedUS Database of Plants Invading Natural Areas in the United States: Common Mullein (Verbascum thapsus). http://www.invasive.org/weedus/subject.html?sub=3080.
USDA, NRCS. 2009. The PLANTS Database (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
Plant Conservation Alliance, Alien Plant Working Group.