Tansy ragwort, Stinking willie
FULL SCIENTIFIC NAME
Senecio jacobaea L.
FAMILY NAME COMMON
FAMILY SCIENTIFIC NAME
Senecio jacobaea is an herbaceous biennial that can grow 20 cm-1 m (8 in.-3.3 ft.) in height. The plant starts out as slightly tomentose, but becomes glabrous by the time it is in full flower. The leaves of the basal rosette look similar to the lower stem leaves, but with reduced internodes. The alternately arranged leaves of the plant are pinnatifid in shape, with the lower leaves having petioles and the upper leaves being sessile. The leaf lobes are oblong and web-shaped. The margins of the leaves are dentate. The leaves can measure between 4-20 cm (1.5-8 in.) long and 2-6 cm (0.75-2.25 in.) wide. The upper surface of the leaves is a medium green color, while the lower surface is lighter in color and sometimes tomentose. There are numerous yellow flower heads on Senecio jacobaea, which appear in July through October. The flower heads measure 1.25-1.6 cm (0.5-0.67 in.) across. They are peduncled and arranged in short, compact corymbs. Each flower head has about 12-15 rays. The rays measure 4-8 mm (0.15-0.3 in.). The involucre measures 4 mm (0.15 in.) in height. The bracts are linear-lanceolate in shape and green, often with a black tip. The fruits are are light brown achenes that measure 2 mm (0.08 in.) long. There are two types of achenes present in Senecio jacobaea. Those produced by disk florets are located at the center of the flower, and have a white pappus that measures from 4 to 5 mm (0.15-0.2 in.) long. Those produced by ray florets at the margin of the flower head do not have a pappus. Page References Fernald 1532, Gleason & Cronquist 559, Holmgren 526, Magee & Ahles 1031, Newcomb 378, Peterson & McKenny 176. See reference section below for full citations.
Senecio aureus L. (Packera aurea (L.) A.& D. Löve) (Golden ragwort) Picture of S. aureus, Tanecetum vulgare L. (common tansy), Sonchus arvensis L. (perennial sow-thistle), S. aureus has basal leaves that are cordate in shape. The stem leaves are greatly reduced compared to S. jacobaea.
Senecio jacobaea reproduces by means of wind-dispersed seeds.
Senecio jacobaea is native to most of Europe, North Africa and western Asia. It has been introduced into New Zealand, Australia, South Africa, North and South America. In Canada, it has been reported from Prince Edward Island, Nova Scotia, and New Brunswick. In the United States, it has been found in the west in California, Oregon, Washington, Idaho, Montana, and Wyoming. In the eastern United States it has been found in Michigan, Illinois, Indiana, New York, New Jersey, and Pennsylvania. In New England, it has been reported from Maine and Massachusetts.
HISTORY OF INTRODUCTION IN NEW ENGLAND
The history of introduction of this weed into New England is largely unknown. It was first reported from various ports on the coasts in the 1900s. In 1904, it was reported from a pasture in Portland, Maine. In 1910, there is a record of it from Danvers, Massachusetts in Essex County. It appears that neither the Portland, Maine, nor the Danvers, Massachusetts populations have persisted to the current time. It was reported from Vancouver, Canada in 1913 and Oregon in 1922. It was likely introduced via contaminated hay brought over from Europe. More recently, in 2002, it has been reported from Barre, Massachusetts in Worcester County. However, the plants seem to have been there for some time prior to this recent report. It appears to have come from wool waste that was spread on the farm fields for fertilizer.
HABITATS IN NEW ENGLAND
Abandoned Field, Agricultural Field, Edge, Open Disturbed Area, Pasture, Railroad Right-of-Way, Roadside, Vacant Lot, Yard or Garden. Senecio jacobaea relies on disturbance to become established. It is highly tolerant of a variety of soil types, as well as salt, and does not appear to have a preference for any particular type.
In the west, Senecio jacobaea is mainly a pest of rangelands, where it can poison cattle and horses. In the 1970s, Oregon lost up to 4 million dollars a year in lost livestock. In the east, it is more of a threat in coastal grasslands as well as pasture land. The plants themselves usually produce 60,000 to 70,000 seeds per plant, with large plants producing 250,000 seeds. These seeds can remain viable for up to 15 years in the seed bank. The plant has not yet become the problem in the east as it has in the west, and steps should be taken to prevent this from occurring.
Documentation required: Herbarium specimen or mounted snippet of a branch with flowers. Best time for documentation: Summer.
Integrated Taxonomic Information System Taxonomic information
PLANTS Database General information and map
California Department of Food and Agriculture - Encylcoweedia Extensive description and control information about Senecio jacobaea and other Senecios
Department of Natural Resources and Environment, Victoria Australia Description and control information
King County Noxious Weeds Description and photographs
Washington State Noxious Weed Control Board Fact sheet with description, images and control information
British Columbia Weed Guide Brief description and images
Andersen, R.N. 1968. Germination and Establishment of Weeds for Experimental Purposes. Weed Science Society of America Handbook. WSSA, Illinois.
Fernald, M.L. 1950. Gray's Manual of Botany 8th ed. American Book Co., Boston.
Gleason, H. A. 1952. The New Britton and Brown Illustrated Flora of the Northeastern United States and Adjacent Canada. Macmillan Publishing Co., Inc. New York.
Gleason, H.A. and A.C. Cronquist. 1991. Manual of Vascular Plants of the Northeastern United States and Adjacent Canada. 2nd ed. New York Botanical Garden, Bronx, New York.
Holmgren, N.H. 1998. Illustrated Companion to Gleason and Cronquist's Manual. New York Botanical Garden, Bronx, New York.
Magee, D.W and H.E. Ahles. 1999. Flora of the Northeast. University of Massachusetts Press, Amherst.
Newcomb, N. 1977. Newcomb's Wildflower Guide. Little Brown, Boston.
Peterson, R.T. and M. McKenny. 1968. A field Guide to Wildflowers of Northeastern and North-central North America. Houghton Mifflin, Boston.
USDA, NRCS. 2001. The PLANTS Database, Version 3.1. (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.