Know Your Natives – Early Buttercup

Early Buttercup (Ranunculus fascicularis) of the Buttercup (Ranunculaceae) family is a late winter, herbaceous perennial, with glossy yellow flowers and tuberous, thickened roots. The genus name is from the Latin for “little frog,” based on the occurrence of many buttercups in moist habitats. The specific epithet is Latin for “clustered,” referring to the roots. In the U.S. the species occurs principally west of the Mississippi River in a broad band from Louisiana and east Texas northward to Minnesota, Wisconsin and Michigan; east of the Mississippi River, scattered occurrences are mapped from Mississippi and Georgia north to New York and New England. In Arkansas, Early Buttercup occurs statewide. Habitats vary from lightly shaded wooded bottomlands to sunny grasslands and even lawns, in moist or dry, loamy, sandy to rocky soils. It is also known as Thick-Root Buttercup.

Early Buttercup, one of 17 buttercup species in Arkansas, is the only species with tuberous roots. The low-growing plants have slender annual tubers (nutrient storage features) and white string-like (filiform) roots. In spring, new white tubers grow around the perimeter of the root crown as the previous year’s now-tan tubers, at the center of the root crown, soften and detach from the root crown. The cylindrical tubers are less than an inch long and ¼ inch wide. Tubers are arranged in a vertical position “hanging” below the round root crown. Plants may have only filiform roots.

Plants tend to occur in scattered seeded colonies with plant density seeming to be greater in more mesic, less sunny sites. Vegetative growth of plants consists of basal leaves and flowering stems, growing directly from the root crown. A cluster of one to several groups of in-facing leaves, on long slender petioles, surrounds one or two flowering stems.

Photo 1: “Hanging” nutrient-storage tubers are replaced annually. As shown, two or three leaf groups are tightly clustered on the root crown. New basal leaves are making their appearance. Photo – March 16.

A mature plant has simple, overwintering, 3-lobed basal leaves and, in late winter into spring, trifoliate compound basal leaves. Overwintering leaves, with blades to 3 inches long and 1 inch wide on a 2 inch petiole, have an obovate terminal lobe and a pair of smaller oblanceolate lateral lobes. Compound leaves have a terminal leaflet and a pair of lateral leaflets, the leaflets entire (uncut) or shallowly to deeply incised. Compound leaves have blades to 2 inches long and 1½ inches wide on a grooved petiole to 4 inches long with a clasping base. Basal leaves are reddish to green above and lighter green below; initially ascending, they become wide-spreading to reclined. Venation is obscure.

Photo 2: Reddish overwintering basal leaves are simple with three prominent lobes (such as the one at far right). Later, basal leaves transition into compound leaves with a terminal leaflet and an opposite pair of lateral leaflets. Photo – March 4.

Early Buttercup is among the first of the Arkansas buttercups to produce flowers in the spring. First buds appear in mid-March, along with the trifoliate basal leaves. First blooms are positioned at center, close to the ground, as lateral stems develop. Each stem (or peduncle) bears 1-6 flowers, ascending to a length of 10 inches, and may have one to several axillary side stems. Although stems may recline to the ground, they do not root.

Photo 3: Basal leaves are displayed in lower portion of photo, with segments of flowering stems in the upper portion. Basal leaves are arranged (left to right) from those outermost in a leaf cluster to those next to the flowering stem. (Flowers removed from some peduncles.) Photo – April 8.

Flowers, in bloom for one day, are ½-1 inch wide with 5 sepals, 5 petals, and a ring of about 50 stamens surrounding about 40 pistils. In bud, the pale green sepals, which may have a persistent burgundy line along the central vein, form 5 prominent bulges. Boat-shaped, low-keeled sepals are wide at base and acute at the apex; they become light yellow with anthesis. Bright yellow petals, less than ½ inch long and ¼ inch wide (and about twice as long as the sepals), are broadest at about the middle with a rounded apex. Their upper surface is an overall glossy yellow, however the lower portion has a greenish tinge. Bright yellow stamens bear 2-lobed anthers, angled toward the flower center. The tightly packed pistils are glabrous with a short, sharply pointed beak (comprising style and stigma) also aligned toward the flower center.

Photo 4: When viewed from the front, flower buds have five “bumps,”an expression created by the boat-shaped sepals. Flowers are at anthesis for a day. Photo – March 5.
Photo 5: Flowers and fruiting heads are on long, pubescent peduncles. New basal leaves are trifoliately compound (right) and cauline leaves have linear to lanceolate blades (lower left). Photo April 2.

Early Buttercup is noticeably pubescent. Plants typically have long straight hairs on stems, pedicels, peduncles, and sepals. The pubescence of petioles and lower stems is appressed. Leaf surfaces tend to be densely short-hairy, the hairs mostly appressed beneath. Pubescence decreases over the growing season. Petals and fruits are glabrous.

Photo 6: Petioles and flowering stems have dense appressed pubescence. As shown, stems are terete and tend to be more pubescent than petioles (leaf stalks). Photo – March 31.

Following anthesis, petals and sepals drop off to expose a spherical head (less than 1/3 inch wide) of developing fruits. Fertilized flowers produce plump, somewhat flattened achenes, less than 1/8 inch wide, with a sharp angled beak (persistent style/stigma) to one side. Dry achenes may be dispersed by surface water flow and passing animals.

Photo 7: Petals, stamens and sepals quickly drop-off to expose a head of developing fruits. Petals and fruits are glabrous. Photo – April 6.

For garden use, Early Buttercup, with its overwintering basal leaves and new leaves and bright yellow flowers in late winter/early spring, would be a nice addition. However, in mesic shady habitats, it may form large colonies by self-seeding so that it may be better suited for wild gardens. Pollen and nectar attract various bees and flies. Seeds are eaten by game birds and small mammals.

Of the 16 other species of buttercups that occur in Arkansas (including 5 non-native species), all except one have glossy yellow flowers. Early Buttercup can be distinguished from most of the other species by noting differences in habitat, plant growth habit, and leaf shape. The plant most likely to be confused with Early Buttercup (especially during winter months) is Hispid Buttercup (Ranunculus hispidus var. hispidus). Early Buttercup can be distinguished from Hispid Buttercup based on: 1) tuberous roots, 2) spring-time leaves that are longer and more narrow, 3) earlier flowers, and 4) appressed hairs, especially along petioles and stems.

Photo 8: Hispid Buttercup (shown here) has similar growth habit and flowers, but leaf shape and pubescence is significantly different. Plant at upper left is Sundrops (Oenothera fruticosa). Photo – April 12.
Photo 9: Flowers of Early Buttercup (left) and Hispid Buttercup (right) are similar, but petals and sepals differ in shape. Early Buttercup may have burgundy lines (as shown) along the keel of their boat-shaped sepals. Squares = ¼ inch.

Article and photographs by ANPS member Sid Vogelpohl

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