Know Your Natives – Ernest’s Spidewort

Ernest’s spiderwort (Tradescantia ernestiana) of the Commelinaceae (Spiderwort) family is an early-blooming, low-growing species, one of the 12 spiderworts that occur in Arkansas. The genus name honors John Tradescant, gardener to Charles I of England, while the specific epithet honors American botanist Ernest Jesse Palmer. This spiderwort occurs in Missouri, Oklahoma, Arkansas, Mississippi and Alabama. In Arkansas, the primary areas of occurrence are the northwestern portion of the Ozark Plateau, the Ouachita Mountains, and higher elevations of the Arkansas Valley. It is also known as woodland spiderwort. The name “spiderwort” has been ascribed to various origins.*

Ernest’s spiderwort occurs in moist sandy to rocky soils in shady to partially shady sites found along wooded slopes, bluffs, woodland edges and lowlands, as well as along drainages and open wet fields. This herbaceous perennial has a multitude of light tan, slender, fleshy roots that radiate outward at shallow depth. Leaves, emerging in mid-winter, are produced in separate basally sheaved, tightly-held clusters, each originating from a separate growth point on a broad, irregular caudex. New clusters develop alongside older clusters and from new growth points around or under the caudex. In favorable sites, dense expanding clumps may form. On any particular plant, a few or many clusters produce a central floral stem.

Photo 1: Some clusters of leaves may produce a floral stem. Inset, showing parts of same plant as in main photo, has arrows indicating developing new clusters. (Leaves damaged by cold temperatures.)

A cluster may have basal leaves only (non-blooming plants) or basal leaves transitioning to cauline (stem) leaves. Leaves higher on stem are spirally arranged and well spaced. Cauline leaves have basal sheaths, tightly wrapped around the stem, with the length of sheath decreasing toward a terminal inflorescence. Largest leaves, at mid-stem, may be to 11 inches long and 1½ inches wide. Leaves are arching and strap-like (broadly linear to lanceolate) and attenuate (gently tapering) to an acute apex. The long, arching and overlapping leaves, in-folded along the upper midrib, give the overall leaf mass an angular appearance. Leaf margins are straight to undulating and entire (uncut). While early leaves are highlighted with reddish shades, later leaves are a lustrous to dull medium green. Leaves are not glaucous (no white coating) and may be glabrous (no pubescence) to puberulent (short soft hairs). Venation is parallel and extends onto sheaths.

Photo 2: First leaves, appearing in mid-winter, may be reddish. Photo – mid March.

Mature plants produce main stems that may have a few secondary stems from the axils of upper cauline leaves. Stems are ascending to arching, glabrous to sparsely pubescent. All parts of the plant are somewhat succulent. With drying soils and warming conditions, plants go dormant by mid-summer; however, with improved conditions, plants may produce new growth. All above-ground evidence of plants disappears soon after they go dormant.

The inflorescences, with blooms from mid to late March into April, are in the form of umbels at the apexes of terminal and secondary stems. Umbels consist of flowers on slender pedicels about an inch or more long, situated between subtending pairs of sessile, leaf-like bracts at the tops of the stems. Pedicels may be glabrous or have short pilose pubescence (thin weak hairs). Length of stems is such that flowers remain within the leaf mass.

When buds first appear, they are pressed together in several stacks. Flowers reach anthesis sequentially, from uppermost to lowermost, initiating bloom when the stem first emerges. With only a few flowers of an umbel in bloom at one time, blooming may continue for a week or two. Buds and flowers are ascending, but after anthesis the spent flowers become nodding to drooping. Flowers open in early morning for a half-day (longer on cooler days).

Photo 3: A clasping, alternate cauline leaf can be seen on left stem along with opposite sessile bracts that subtend the inflorescence. Note tightly stacked buds on right stem. Photo – early April.

Flowers of separate plants range from light to dark pink, blue and purple (rarely white), with the color being shared by petals, filaments, wispy filament hairs, and style. Flowers, to 1½ inches in diameter, have three triangular, light green, boat-shaped sepals. When in bud, sepals are positioned margin-to-margin, forming a tear-drop-shaped calyx. At anthesis, the flower’s three sepals (½ inch long, ¼ inch wide) and three petals spread wide with tips of sepals positioned between petals. Petals are broadly ovate to almost orbicular and very showy. Upper petal margins are variously flexed and may be slightly irregular. Flowers have six ascending stamens with bright yellow anthers and exquisitely beautiful, wispy filament hairs, each hair consisting of single cells visibly connected end-to-end. The colored style, broader than the filaments, bears a white, terminal stigma. The plump ovary is three-chambered. With the passing of anthesis, the calyx again becomes tear-drop shaped and persists into fruiting. The exterior of the sepals is covered with dense, long, pilose pubescence.

Photo 4: Flowers may be light to dark pink, blue or purple. Note the six stamens (with wispy hairs and lobed anthers), single style atop a triangular ovary, and tips of sepals between the petals.
Photo 5: Calyxes, on growing pedicels, are positioned upright in bud and flower, but droop after anthesis. Plant to right is rose vervain (Glandularia canadensis).

With fertilization, three-chambered capsules form that have central placentation. The oval capsules dehisce (split) at their top and sides, spreading wide with the three sections positioned between the sepals. A capsule may produce a half dozen or so flattened, round gray seeds.

For a partially shaded to shady natural area that has moist to wet soils, Ernest’s spiderwort may be a desirable plant. Its mid-winter attractive growth provides early evidence of spring and its early flowers are a highlight of the season. Flower color of various plants varies from light to dark pinks, blues and purples. In more favorable sites, even a large plant remains a non-aggressive self-seeder. Plants disappear in summer, but may have re-growth when conditions improve.

Photo 6: Ernest’s spiderwort can form clumps. In comparison to some other taller spiderwort species, flowers mostly remain within the leaf mass.

Spiderwort species (Tradescantia spp.) are notoriously difficult to tell apart. In Arkansas, five common and seven uncommon spiderworts have been recorded. Characteristics of Ernest’s spiderwort that may help distinguish it from other spiderworts include 1) preference for shady sites, 2) early inflorescence, 3) darker flower colors, 4) wider leaves, 5) shorter clumping habit, and 6) pilose pubescence mostly on sepals and pedicels.

In Arkansas, similar species in similar habitats, easily confused with Ernest’s spiderwort, are the uncommon Ozark spiderwort (Tradescantia ozarkana) and the uncommon Virginia spiderwort (Tradescantia virginiana). Flowers of Ozark spiderwort are lighter colored (usually white) and have smaller sepals. In Arkansas, its range overlaps with Ernest’s spiderwort, and the two are known to hybridize. Virginia spiderwort typically has blue flowers and narrower leaves. It is at present only found in eastern Arkansas, outside of the range of Ernest’s spiderwort.

*   The term “spiderwort” has several possible origins: 1) leaf arrangement that looks like a “squatting” spider, 2) webby hairs on filaments, and 3) sap of stem can be drawn out into a webby string.

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