Buttercup family (Ranunculaceae)
Description: This herbaceous plant is a biennial or short-lived perennial up to 2' tall that branches occasionally. The green stems are glabrous. The blades of the basal leaves are up to 2" long and 2½" across; they are orbicular-reniform and crenate along the margins. Their petioles are up to 3" long. The lower cauline leaves are up to 2" long and across on petioles up to 1" long; they are often deeply divided into 3 rounded lobes and their margins are crenate. The upper cauline leaves are usually lanceolate, oblanceolate, or oblong with smooth margins; sometimes they are shallowly lobed with teeth that are crenate or dentate. The blades of the upper cauline leaves are up to 1½" long and they are sessile. All of these leaves are hairless; the cauline leaves alternate along the stems. Each upper stem terminates in 1-3 flowers on individual stalks. Each flower is about ¼" across, consisting of 5 yellow petals, 5 green sepals, a cluster of green carpels, and a ring of stamens with bright yellow anthers. The petals are broadly lanceolate or triangular; they are smaller than the sepals. The sepals become membranous with age and they fall off the flower at about the same time as the petals. The blooming period occurs from mid-spring to early summer and lasts about 1-2 months. The cluster of carpels (immature achenes) elongates to about ¼" in length and becomes ovoid in shape. The small achenes are somewhat flattened and orbicular in shape; their surfaces are shiny when mature and they have very small beaks. The root system consists of a tuft of fibrous roots. This plant spreads by reseeding itself.
Cultivation: This plant is typically found in partial sunlight, moist to mesic conditions, and a reasonably fertile loam or clay-loam soil. It has few problems with pests and disease.
Range & Habitat: Small-Flowered Buttercup is a common native plant that has been observed in nearly all counties of Illinois (see Distribution Map); it probably occurs in the remaining counties as well. Habitats include open woodlands, woodland borders, areas along woodland paths, degraded meadows, banks of rivers and ditches, pastures and abandoned fields, edges of yards, vacant lots, grassy areas along railroads and roads, and waste areas. This plant is typically found in disturbed areas and is somewhat weedy.
Faunal Associations: Ladybird beetles, small bees, Syrphid flies, and other kinds of flies suck nectar from the flowers. Some flies and ladybird beetles feed on the pollen, while some bees collect pollen for their larvae. Ants suck nectar that adheres to the carpels after the petals and sepals fall of the flowers. The Wood Duck and Wild Turkey eat the foliage and seeds of Ranunculus spp. (Buttercups). Some small rodents, including the Eastern Chipmunk and Meadow Vole, eat the seeds, while the Cottontail Rabbit eats the foliage. However, the use of the foliage and seeds as a food source by these animals is rather limited. The foliage contains a blistering agent and is mildly toxic to livestock.
Photographic Location: The upper photograph was taken at the edge of a yard in Urbana, Illinois, while the lower photograph was taken of a plant growing along a woodland border in the same city.
Comments: Small-Flowered Buttercup is one of the most common Ranunculus spp. in Illinois. The flowers aren't very showy and this plant is easily overlooked. There are many Ranunculus spp. in the state and they are often hard to tell apart. While attempting to identify Small-Flowered Buttercup, look for lower leaves that are orbicular, kidney-shaped, or deeply 3-lobed with crenate margins, and slender upper leaves with mostly smooth margins. The foliage is usually hairless, although there is an uncommon form of this plant that is finely pubescent. Small-Flowered Buttercup is very similar in appearance to Ranunculus micranthus (also called Small-Flowered Buttercup); the latter species is restricted to the southern half of Illinois. To distinguish Ranunculus abortivus from Ranunculus micranthus, it is often necessary to examine the naked receptacles of these two species (the receptacle of the flower is what remains after the carpels, sepals, and petals are removed). The receptacle of Ranunculus abortivus is pubescent, while the receptacle of Ranunculus micranthus is hairless. Another difference is the following: the achenes of Ranunculus abortivus have a shiny surface, while the achenes of Ranunculus micranthus have a dull surface.