Kidneyleaf Buttercup is a native, erect, branched perennial, growing on smooth but faintly ridged stems, 8-20 inches high.
The leaves are both basal and stem and unlike the other 3 buttercups in the Garden, the basal and stem leaves are very different. Basal leaves are kidney or heart-shaped, hence the common name. They are on long stems and usually undivided but sometimes the inner most leaves can be 3-parted. The tips have a least 5 large rounded teeth - some would say small lobes. Stem leaves are alternate, few, usually stalkless, but deeply lobed with 3-5 oblong lobes, like many other buttercups.
The inflorescence consists of a number of solitary stalked flowers rising from the upper leaf axils.
The flower is 5 parted, but very small, 1/4 inch wide. There are normally 5 recurved sepals that are without hair, longer and wider than the narrow yellow petals which are some of the smallest in the Buttercup family. In the center is a cluster of green carpels, with very short styles, surrounded by a ring of stamens that have greenish-yellow filaments and yellow anthers. The nectaries of the flower are in a pocket around the base of the petals. A true corolla is lacking.
Seed: Mature fruit is an oval cluster of dry achenes each of is 1.4-1.6 × 1-1.5 mm in size with a very small curved beak. Buttercup seeds need some cold stratification for germination, at least 30 days and some species require 60 days.
Varieties: Three have been listed in the literature but Flora of North America (Ref.# W7) does not consider it necessary to subdivide the species.
Toxic: Buttercups have hazardous properties - see notes below.
Habitat: Buttercups comprise about 275 different species. Kidneyleaf Buttercup grows in rich moist soil of woods, meadows, fallow fields and clearings. Plants can survive standing shallow water for short periods. It grows from a fibrous root system with the bottom of the stem sometimes enlarged.
Names: Ranunculus abortivus is in Ranunculus Sect. Epirotes. The generic name Ranunculus, is from two Latin words, 'rana' meaning ' frog' and 'unculus' meaning 'little' and together they refer to a group of plants, many of which grow in moist places - like little frogs. The species, abortivus, is from the Latin aborior, meaning 'pass away' or 'aborted'. The use of abortivus is then usually meant to mean - 'parts missing' or 'showing arrested development' which may be a reference to petals of the flower that are quite small, but we are not certain if that is what Linnaeus had in mind. The family name of Buttercup, used to be "Crowfoot', hence the continuation of the 'Crowfoot' in many of the species common names. The author name for the plant classification, 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: While the difference of basal and stem leaves of this species are unique, here are a few other buttercups for comparison: Cursed Crowfoot, R. sceleratus; Swamp Buttercup, R. hispidus; Tall Buttercup, R. acris; Hooked Crowfoot, R. recurvatus; Bristly Buttercup, Ranunculus pensylvanicus. The flower of R. abortivus most closely resembles that of R. recurvatus.
Above: Example of Kidneyleaf Buttercup. Drawing above from ©USDA-NRCS. Wetland flora: Field office illustrated guide to plant species. USDA Natural Resources Conservation Service.
Below: The longer and wider greenish sepals are visible in this pair of photos. The green carpels in the center are surrounded by a ring of stamens with yellow anthers. The small petals are some of the smallest among the Buttercups.
Below: 2nd photo - The stem leaves are deeply 3 to 5 lobed and stalkless, far different from the kidney shaped basal leaves (1st photo) which are on long stalks with coarse rounded teeth on the margins.
Below: 1st photo - The green stem is smooth but faintly ridged. 2nd photo - The maturing seed head and seeds. Note the very small curved beak on each seed.
Below: A basal clump of leaves developing which submerged in early May.
Notes: Kidneyleaf Buttercup is indigenous to the Garden area; Eloise Butler catalogued it on May 25, 1907. Martha Crone noted it in bloom in 1939 and listed it on her 1951 Garden Census under the name Small-flowered Buttercup. It has been listed on subsequent census reports. It is native to Minnesota, being found in all counties with a few scattered exceptions near the western border. R. abortivus is one of 16 buttercup species found in Minnesota. It is found throughout North America except in the U.S. states of OR, CA, NV, UT and AZ.
Toxicity: Many of the species of Ranunculus are poisonous and will severely irritate the skin. If taken internally the plant can cause stomach inflammation. Cattle can be affected if they eat the plant. When the plant is dried, however, the poisonous material evaporates. Bees have been poisoned when they pick up pollen from Ranunculus species. - see this article on bees - pdf.
Legend: The legend of this plant family is this: Ranunculus, a Libyan boy who sang very beautifully, always wore green and gold silk. While singing in the woods, wood nymphs heard him and to get some peace and quiet, they turned him into a green and gold flower.
Eloise Butler wrote the following about Buttercups: "A number of the early flowering plants are members of the crowfoot family [Ranunculaceae -in current times this family is now called the Buttercup Family], [such] as the anemones and buttercups. In the divided leaves of a crowfoot, as some of the buttercups are called, the early botanists saw a resemblance to a bird’s foot. The buttercups of Minnesota are not so much in evidence as the tall European buttercup [Ranunculus acris L.] the pest of the hay fields - farther east.
One early species, Ranunculus abortivus, [Littleleaf Buttercup] has so small a flower that a novice would scarcely notice it, and is surprised to hear it named a buttercup. Neither would a child be likely to apply the time-worn test of holding the flower to your face to learn if you love butter. This lowly buttercup [her text omits the common name] blooms sparsely on the prairie with the pasque flower. The specific name rhomboideus [prairie buttercup] indicates the shape of the leaf. The low, tufted R. fascicularis [early buttercup] has a larger flower, but is not conspicuously massed. Our two prettiest buttercups are aquatics - one with shining, yellow petals; the other with smaller white flowers and long, railing stems; and both bearing finely dissected leaves.
The large Crowfoot family is without strongly marked characters. Its plants have usually an acrid taste; the leaves are generally more or less cut or divided; the corolla is often wanting, and, when this is the case, the calyx is colored like a corolla; the stamens are numerous; the pistils vary in number from one to several; and all the parts of the flower are distinct or unconnected." Published April 30, 1911, Minneapolis Sunday Tribune [Entire Article]
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"