Description: Wild parsnip is a biennial
with alternate, dark green leaves, and a deep, fleshy taproot.
The first year wild parsnip grows as a rosette for at least
one year, then sends up an erect, hollow, grooved stem. The
flat-topped flower head is yellow to yellowish-red from which
flattened, circular, brown seeds are produced. Wild parsnip
can be identified from wild carrot and other parsley’s
by its yellow flowers, square-like stem, and its pinnately
compound leaves that are divided once into more than five
leaflets. Wild Parsnip grows from 1-6 feet tall.
Distribution: Wild parsnip is found extensively in
Johnson County. It can be found in moist, rich, alkaline soils
in roadsides, ditches, pastures, and waste places.
What’s The Problem?: Leaves of wild parsnip
contain the substance "psoralen", which may be transferred
to the skin via contact with the sap or foliage, and increase
the skin’s sensitivity to ultraviolet light. Many people
are sensitive to the touch of the leaves and can develop a
rash if their skin comes into contact with the leaves or sap
while the sun is shining. A poison ivy-like rash can occur,
with severe blistering and peeling. Some people say the rash
and blistering is similar to a 2nd degree sunburn. This rash
may take 2-3 weeks to fade. Wild parsnip also produces very
abundant seed and can spread rapidly into new areas to compete
with more beneficial native plants.
Management Methods: When attempting management of
this weed, care should be taken to protect skin from the irritating
sap. Wear gloves, long sleeves, pants, and boots. Good control
can be achieved through hand pulling of small infestations
before seeds develop. Hand cutting of the plant below the
root crown can also be effective. Mowing is another good tool
if done before seed sets. Mowing, however, may reduce competitiveness
of other plants in the area. Use of herbicides can be a viable
alternative in large infestations. Be certain to correctly
identify plants and use the proper chemicals at labeled rates.
Be sure to read and fully understand chemical labels before
usage. Prescribed burning will not control wild parsnip, as
it removes litter and increases amounts of sunlight to young
plants. However, regular burning may increase the vigor and
competitiveness of local plants, possibly decreasing wild
parsnip populations. Establishment or maintenance of a competitive
ground cover can be an excellent tool to control or prevent
wild parsnip infestations.
Photo couresy of Weeds of Nebraska and the Great Plains published by Nebraska Department of Agriculture
Photo courtesy of K.R. Robertson, Illinois Natural History Survey