SPECIES CHARACTER
Description
The thick taproot of the wild parsnip is long, conic, and fleshy. Branching from
the fleshy root is the light green, hollow, deeply-grooved stem that stands erect
at 2-5 feet (0.6-1.5 meters) tall. Leaves are alternate, pinnately compound, and
branched with saw-toothed edges. Each leaf has 5-15 ovate to oblong leaflets with
variably toothed edges and deep lobes. The petiolate lower leaves are often 1.5
inches (3.8 cm) long, while upper leaves are sessile and much reduced. The small,
5-petaled, yellow flowers are arranged in 2-6 inch (5-15 cm) broad umbels at the
top of slender stems and branches. Each compound flat umbel has 15-25 primary rays
that contain yellow blossoms during the June-September flowering season. The
blossoms give rise to a fruit termed a schizocarp that is broadly oval and 0.25 inch
(6 mm) long. The abundant 0.25 inch (6 mm) mericarps (segments of the fruit) of
this parsnip are flat, round, smooth, straw-colored, and have low ribs across them.
Similar Species
Wild parsnip is distiguished from other species in the parsley family by its yellow
flowers and its pinnately compound leaves that are divided once into more than five
leaflets. Wild parsnip should be accurately identified before attempting any control
measures. If identification of wild parsnip is in doubt, the plant's identity should
be confirmed by a knowledgeable individual and/or by consulting appropriate books.
Distribution
This member of the parsnip or umbel family has escaped from cultivation and is common
throughout the northern United States and Canada, from British Columbia to California
and Vermont, and south to Florida. In Illinois, wild parsnip has become a serious
problem in some mesic prairies, and it has been recorded from every county.
Habitat
Although this Eurasian native thrives when growing in rich, alkaline, moist soils, it
can survive under almost any condi-tions. Wild parsnip commonly can be found along
roadsides, in pastures, and in fields.
Life History
Wild parsnip is a perennial that exists as a basal rosette for at least one year and
then flowers and dies. Like its relative the carrot, wild parsnip produces a rosette
of large, grooved, upright leaves and stores reserves in a large, fleshy taproot during
the first year. A hollow flowering stem whose leaves are much smaller is sent up from
the center of the rosette in a subse-quent growth season. Wild parsnip often flowers
and sets seed during its second year, although it may not flower until subsequent years.
The edible roots of wild parsnip were consumed in ancient Greece and Rome and cultivars
are still grown for food today. The root develops its sweet taste after being exposed to
cold. Some people are sensitive to the touch of the leaves and soon develop a rash if
their skin contacts the leaves or plant sap in the presence of sunlight. A very painful
rash can develop that in some people leaves scars that can persisit for several months or
longer. Wild parsnip is most irritating at the time of flowering.
Effects Upon Natural Areas
Well-established prairies are not likely to be invaded by parsnip, but it can become quite
abundant on prairie edges and in disturbed patches within otherwise high-quality prairies.
Once established at the edges, parsnip can spread into adjacent high-quality areas.
CONTROL RECOMMENDATIONS
Warning-- Care should be taken to avoid skin contact with the toxic sap of the plant
tissues by wearing gloves, sleeves, and long pants.
Although eradication of this exotic is desirable from a human safety as well as ecological
standpoint, in some situations the best control measure is to do nothing. In high-quality
prairies, aggressive growth by other species sometimes can outcompete and eventually
displace the parsnip.
Mechanical
The best control is achieved mainly through hand-pulling. Plants should be pulled and
removed so that seeds do not develop and plants do not resprout. Wild parsnip is easiest
to pull right after a good rain or during a drought when the root shrinks. Another
effective practice involves cutting the plant below the root crown before seed set during
spring of the second year. The best time is as soon as blooms show, but have not matured.
Since the plants do not all flower at once, the area should be rechecked several weeks
after the first cutting and the following 2-3 years for newly flowering plants. After a
spring burn, wild parsnip rosettes are among the first plants to emerge and may be detected
easily and dug out to control its abundance along prairie edges. Seeds do not remain viable
if dormant in the ground more than 4 years, so the species can be controlled if there is
no outside seed source. Although the practices of hand-pulling, cutting, and digging have
been successful in small areas with scattered plants, these practices can become difficult
and time-consuming if patches containing hundreds of plants have been allowed to spread
unchecked.
Mowing or cutting the base of the stem with a scythe can be effective if it takes place
after flowering the second year when the plant is mature and blooming, but before seed
set. Parsnip must be remowed or recut often and checked later for small bloom shoots near
the ground. Poorly timed mowing, as is likely along roadsides, may increase both number
of seedlings and percentage surviving to maturity. Mowing probably favors parsnip
maturation by allowing more sunlight to reach immature parsnip plants, which are too low
to be damaged by the mower. Mowing also reduces the density, height, and flowering of
other species that are potentially good competitors against parsnip, such as common
goldenrod.
Chemical
If mechanical methods have failed to control wild parsnip or are not feasible, a 2% spot
application of the herbicide Roundup (glyphosate) to basal rosettes is a recommended
treatment. Roundup should be applied to individual plants with a hand sprayer in late
fall after most native vegetation is dormant. Late fall application minimizes the
potential harm to nontarget species. It may be necessary to treat the same area again
annually until missed plants and plants originating from the seed bank are eliminated.
Roundup is a nonselective herbicide (kills all vegetation) and should not be used in
high-quality natural communities during the growing season because of the possibility of
harming nontarget plants.
The herbicide 2,4-D (available under a variety of trade names) mixed according to label
directions and applied to individual parsnip basal rosettes between March-May or August-
October is effective. This herbicide should only be used on buffer or severely disturbed
sites, and not in high-quality natural communities if it is applied during the growing
season. Repeated early spring applications of this chemical before the flower stalk begins
to elongate will reduce infestation of wild parsnip.
Care should be used to avoid contacting nontarget plants when applying either herbicide.
Do not spray so heavily that herbicide drips off the target species. Native nontarget
species will be important in recolonizing the site once the parsnip dies. The herbicide
should be applied while backing away from the treated area to avoid contact with wet
herbicide. By law, herbicides only may be applied according to label instructions and by
licensed herbicide applicators or operators when working on public properties.
FAILED OR INEFFECTIVE PRACTICES
Burning does not successfully control parsnip be-cause it removes litter and taller plants,
providing favor-able condi-tions for parsnip rosettes to develop. However, periodic
burning maintains the vigor of native plants, allowing them to compete with parsnip.
The parsnip webworm damages some individual plants severely, but is not known to eradicate
whole patches and is not likely to be useful as a biocontrol agent.
REFERENCES
Eckardt, N. 1987. Element stewardship abstract for Pastinaca sativa - wild parsnip. The Nature Conservancy, Arlington, Virginia. 4 pp.
Fernald, M. L. 1950. Gray's Manual of Botany, eighth edition. American Book Co., New York. 1632 pp.
Jaques, H. E. and R. E. Wilkinson. 1979. How to know the weeds, third edition. William C. Brown Co. Publishers, Dubuque, Iowa. 323 pp.
Jeffery, L. S. and H. J. Lorenzi. 1987. Weeds of the United States and their control. Van Nostrand, Reinhold Co., New York. 257 pp.
Kline, V. M. 1981. Mowing to Control Wild Parsnip (Wisconsin). Restoration and Management Notes 1(1):33.
Kline, Dr. V. M. 1976. Effects of mowing on wild parsnip: six year study (Wisconsin). Restoration and Management Notes 4(2):113.
Mohlenbrock, R. H. 1986. Guide to the vascular flora of Illinois. Southern Illinois University Press, Carbondale. 507 pp.
PERSONAL COMMUNICATION
Abrell, Brian. 1988. Division of Nature Preserves, Department of Natural Resources, Indianapolis, Indiana.
Apfelbaum, Steve. 1988. Applied Ecological Services, Juda, Wisconsin.
Betz, Robert. 1988. Northwestern University of Illinois, Chicago, Illinois.
Martin, Mark. 1988. Wisconsin Department of Natural Resources, Madison, Wisconsin.
Nyboer, Randy. 1988. Division of Natural Heritage, Illinois Department of Conservation, Springfield, Illinois.
Written for the Illinois Nature Preserves Commission by:
Jill Kennay and George Fell
Natural Land Institue
320 South Third Street
Rockford, Illinois 61108