On moist ground, Water Parsnip initially forms a rosette of
basal leaves up to 1½' across. In shallow water, this
initially forms a cluster of aquatic or semi-aquatic leaves of variable
length. The terrestrial basal leaves are very similar to
the alternate leaves (described below), except the leaflets of
former are wider. Fully aquatic leaves are double-pinnate or
filiform leaflets or lobes that are pale green and glabrous.
Semi-aquatic leaves are primarily odd-pinnate with linear to
linear-lanceolate leaflets; these leaflets usually have narrow pointed
lobes along their sides. In addition, semi-aquatic leaves may have
whorls of secondary leaflets at the bases of the primary leaflets.
These secondary leaflets are similar to the primary leaflets, except
the former are smaller in size.
Regardless of which kind of leaves has
been developed, this is followed by a flowering plant 2½-6' tall (above
the ground or water surface) that branches sparingly. The stems of the
flowering plant are light green, glabrous, and longitudinally veined;
they are terete or angular-terete in cross-section. Alternate leaves
along the stems are up to 1½' long and about one-half as much across;
they are odd-pinnate with 7-17 leaflets. The leaflets of these compound
leaves are 1½-4½" long and ¼-1¼" across; they are linear-lanceolate to
narrowly lanceolate in shape and their margins are finely serrated. The
upper surface of these leaflets is medium green and glabrous, while the
lower surface is pale green and glabrous. The lateral leaflets are
sessile, while the terminal leaflet of each compound leaf has a short
petiolule (basal stalklet) up to 1" long. Each compound leaf has a
sheath that extends along the entire length of its petiole (¼-4" long);
the lower leaves have longer petioles than upper leaves. Both the
petiole and rachis of each compound leaf is medium green, glabrous, and
angular; they are often finely grooved along their upper surfaces.
upper stems terminate in compound umbels of flowers that span 2-5"
across; these umbels are flat-topped and their peduncles are 1-5" long.
Each compound umbel is divided into 8-22 umbellets, and each umbellet
has 20-35 flowers. Each flower spans about 1/8 (3 mm.) across,
consisting of 5 white petals with incurved tips, a short light green calyx
with insignificant teeth, 5 exerted stamens, and a 2-celled ovary with
a pair of divergent styles. The peduncles, rays, and pedicels of the compound umbels are light
to medium green, glabrous, angular, and often finely grooved. The
blooming period occurs from mid-summer to early fall, lasting about 1½
months. Each flower is replaced by an oblongoid-ellipsoid fruit about
1/8" (3 mm.) long that is slightly compressed and strongly ribbed; each fruit consists of a
pair of seeds that are joined together. The root system consists of
shallow fibrous roots that are slightly fleshy.
The preference is full or partial sun, shallow water (up to 1½' deep)
or wet ground, and soil that is mucky or sandy. Depending on its level
of exposure to standing water, Water Parsnip may produce terrestrial,
semi-aquatic, or fully aquatic leaves during the early stages of its
The native Water Parsnip is
occasional throughout Illinois (see Distribution
of soggy thickets, wet prairies, marshes, bottoms of seeps, low areas
springs, swamps, borders and shallow water of ponds, and ditches. This
wildflower is found in both sandy and non-sandy wetland habitats.
The flowers can attract a wide variety of
including Halictid bees, plasterer bees (Colletes spp.
Sphecid wasps, spider wasps, cuckoo wasps
(Chrysididae), Chalcid wasps, Eucoilid wasps, Ichneumon wasps, Braconid
wasps, Vespid wasps, flower flies (Syrphidae), bee flies (Bombyliidae),
Tachinid flies, flesh flies (Sarcophagidae), Muscid flies, Callophorid
flies, frit flies (Chloropidae), leaf beetles (Chrysomelidae), ladybird
beetles, and tumbling flowering beetles (Mordellidae). These insects
obtain primarily nectar from the flowers (Robertson, 1929). Both adults and larvae of a
leaf beetle, Prasocuris
, feed on the foliage of Water
Parsnip. Unlike some wetland species in the Carrot family with white
flowers, the foliage of Water Parsnip is not regarded as toxic to
Photos of the terrestrial plant were taken at a sandy marsh at the
Heron Boardwalk in
Vermilion County, Illinois. The photo of the semi-aquatic leaf was
taken at the edge of a sandy swamp at the Irwin Prairie State Nature
in NW Ohio.
Water Parsnip is unusual in the variability of its leaves: they can be
terrestrial, semi-aquatic, or aquatic. To make matters even more
confusing to the novice, its terrestrial leaves can vary considerably
in the width of their leaflets. It is also easy to confuse Water
Parsnip with other white-flowered species in the Carrot family that
prefer wetland habitats. Generally, these other species have fewer
teeth along the sides of their leaflets and they produce neither
aquatic or semi-aquatic leaves, even when they are found in standing
water. Other key characteristics to consider while making an
identification include whether the umbels of flowers are flat-topped or
dome-shaped, whether the compound leaves are simple-pinnate or
double-pinnate, and whether there are any floral bracts underneath the
umbels or any floral bractlets underneath the umbellets.