Buttercup family (Ranunculaceae)
This is a herbaceous perennial plant about ¾–3' long. In its habit of
this plant is a submerged aquatic (sometimes with floating leaves),
emergent aquatic, or terrestrial; it
has branching stems and highly variable foliage. In general, the stems
are light green to medium green, terete, glabrous. Alternate leaves
occur along the entire length of these stems below the inflorescence;
they are medium green, glabrous, and divided into compound palmate
lobes. Regardless of habit of growth, the leaves are 1–3½" across and
1–3" long. For submerged plants, the leaves are deeply lobed; they are
ultimately divided into tertiary (3-divided) or quaternary (4-divided)
lobes that are filiform-linear in shape. In outline, these submerged
leaves are reniform, orbicular, or fan-shaped. Usually the submerged
leaves are nearly sessile to short-petiolate, although sometimes their
petioles are up to 1½" long. For emergent aquatic or terrestrial
plants, the leaves are
moderately to deeply lobed; they are ultimately divided into secondary
lobes that are narrowly oblong to oblong. If they are present,
the uppermost leaves of these plants are usually
smaller in size and less divided. In outline,
the emergent aquatic or terrestrial leaves
are reniform, orbicular, or deltate. The petioles of these leaves are
length (¼–3" long).
narrow inflorescence is 3-12" long, consisting of either a long-stalked
solitary flower or a branching stalk with 2-12 flowers; the flowers of
an inflorescence are held above the water. Both the central stalk and
pedicels of the flowers are light green, glabrous, terete, and
relatively stout (although hollow within). Each flower is about ¾"
across, consisting of 5-6 yellow petals (rarely more), 5 light
green to pale yellow sepals, a ring of numerous yellow to golden yellow
stamens, and a central head of pistils that is light green to yellow.
The petals are oval or obovate in shape with rounded tips. The sepals
are broadly elliptic or ovate in shape and either widely spreading to
somewhat declined; they are about one-half as long as the petals. The
blooming period occurs from late spring to mid-summer, lasting about
1-2 months. Afterwards, the flowers are replaced by small heads of
achenes. Individual mature achenes are about 2 mm. long and
ovoid-flattened in shape; the beaks near their apices are about 1.5 mm.
long. These achenes have the capacity to be carried by water currents,
or they can be blown about by the wind on the surface of water. The
root system is shallow and fibrous. Sometimes rootlets develop from the
lower nodes of stems when they establish contact with wet ground.
Colonies of plants often occur.
The preference is
full or partial sun, shallow quiet water (up to 2' deep) to wet ground,
and soil containing either mud or sandy mud. The location should
not be subjected to strong water currents, high wind, or large waves.
& Habitat: The native Yellow Water
Buttercup is occasional in most
areas of central and northern Illinois, while it is uncommon in the
southern section of the state (see Distribution
This plant is
widely distributed in the NE, Midwest, Pacific NW, and other areas of
the United States. It also occurs in parts of southern Canada. Habitats
include shallow water and shores of ponds, shallow creeks or streams
with slow-moving water, swamps, seep bottoms, and deep ditches.
This plant is usually found in high quality wetland habitats.
Associations: The flowers are cross-pollinated
primarily by bees,
flies, and beetles (especially Prasocuris spp.).
Both nectar and pollen
are available as floral rewards to such visitors. The beetles may also
gnaw destructively on the flowers and exposed leaves. Even though the
foliage is somewhat toxic, some vertebrate animals use water buttercups
as a minor source of food. The foliage and/or seedheads are eaten by
the Trumpeter Swan, Muskrat, Wood Duck, Snapping Turtle, and Blanding's
Turtle (Martin et al., 1951/1961; Bellrose, 1942/1976; Lagler, 1943).
The finely divided aquatic leaves and low terrestrial leaves provide
cover for insects and other small invertebrates.
A sandy swamp at Indiana Dunes State Park in NW Indiana, and the bottom
seep at Horseshoe Bottoms in Vermilion County, Illinois.
The flowers of Yellow Water Buttercup (Ranunculus flabellaris)
brightly colored and showy, especially when they bloom together in
large plant colonies. This plant is remarkable in its ability to adapt
to different wetland habitats by changing the morphology of its leaves.
As a result, a leaves of a fully aquatic plant and the leaves of a
terrestrial plant have little in common in terms of their appearance,
except that they are both palmately divided into lobes. Nonetheless,
their flowers and achenes are the same. The transformation of the
leaves is strongly influenced by exposure to water and also by
temperature. The only other semi-aquatic buttercup with yellow flowers
in Illinois is Ranunculus gmelinii, or Small Yellow
This latter species occurs in Cook and Menard counties, where it is
rare. Small Yellow Water Buttercup is smaller in size overall; it has
smaller flowers (about ½" across), inflorescences with fewer flowers
(typically 1-4), less divided leaves, and achenes with shorter beaks.
For example, the lower terrestrial leaves of this species are shallowly
to moderately divided into lobes; they are ultimately divided into
secondary lobes. In contrast, the lower terrestrial leaves of Yellow
Water Buttercup are moderately to deeply divided into lobes; they are
ultimately divided into tertiary lobes.