Know Your Natives – White Crownbeard

White crownbeard or white wingstem (Verbesina virginica) of the Aster, Sunflower, or Composite (Asteraceae) family has tall winged stems with domed clusters of white flower heads. In the U.S., it is found primarily from central Texas up through southeast Kansas, across to Maryland and thence to the Atlantic and Gulf Coasts. In Arkansas, the species occurs statewide. The genus name is based on resemblance of the leaves to those of species of verbena. The specific epithet refers to the original description of the species from Virginia. Preferred habitat is partial sunlight found in open, low-lying woodlands and thickets in well-drained mesic soils.

This perennial herb has a woody misshapen root-crown with tough ropy roots. The crown slowly enlarges by forming knobby side-growths from which arise new stems. The core of the crown dies, but persists. Older plants in sunnier sites may produce a half-dozen or more stems.

Photo 1: This 4-inch wide root-crown shows six to eight years of knobby growth. This particular crown supported two green stems; one off-photo to right and one that broke off the partially dead root growth at far left.

Erect, stout, 6-7 ft stems are straight and unbranched except for floral branches near the apex. From ground-level to near the floral branches, stems have prominent fleshy longitudinal wings (see below) and dense short (tomentose) pubescence. With freezing temperatures, “frost flowers” form along green stems and, later, from the base of previously frozen stems––an alternate common name is “frost weed”. Frozen stems often persist into the following year.

Photo 2: Characteristic large leaves and winged stems in spring. Photo – April 12.
Photo 3: Straight, stout stems are not branched except for upper floral branches. Photo – September 6.

White crownbeard has large, widely spaced, alternate cauline leaves. Larger leaves are oval to lanceolate-elliptic while the much smaller leaves on floral branches and within the inflorescence are lanceolate. Largest leaves, at mid-stem, may be 7-10 inches long and 2-4½ inches wide, including a 2-inch petiole. Leaves are short-hirsute (sandpapery) above and downy-puberulent beneath. Blade margins may be entire or have widely spaced small teeth. Lower leaves tend to drop-off late in the growing season.

The leaf margins narrow to winged petioles, the wings extending down the stem in an intriguing mathematical pattern. With the alternate leaves being cyclic, the left petiole wing (at stem side view) extends as a cauline wing to the next-third-leaf below while the right petiole wing of the same leaf extends to the next-fifth-leaf. In cross-section, the wing-bearing portion of stems has five wings. Venation of the cauline wings is perpendicular to the stem (as are veins of petiole wings). Petiole and cauline wings are about ⅛-inch wide.

Photo 4: Petioles are winged by the decurrent leaf blade their entire length. Petiole wings extend straight down stems where they terminate just above a lower petiole. Note venation of leaves and wings. Photo – May 20.

The inflorescence, from August to October, produces round-topped, terminal clusters of 2-4 flower heads 1-1½ inches across. Heads are subtended by pale green, elongate involucres comprising a dozen or so elongate phyllaries (sepal-like bracts) in one or two series. Flower heads have 1-5 pistillate (no stamens) ray florets and 7-15 perfect (pistil and stamens) disk florets. All parts of the inflorescence are densely puberulent.

In bud, the whitish green flower heads (involucres) have an inverted bell shape with ribbed sides and a flat top. Glabrous white disk florets, ¼ inch long and 1/16 inch wide, are tubular with five short acutely triangular, spreading lobes. Disk florets have five stamens topped with dark purple elongate anthers, fused into a ring. After the white pollen is exposed by the white style rising through the anther ring, the style splits and recurves to expose elongate stigmatic surfaces.

The smaller glabrous white ray florets have widely spreading, oval to broadly oblong corollas (ligules) with rounded, notched tips and cupped margins. The white styles of the ray florets also become exserted, split and recurve.

In Composite family florets, the ovaries are said to be “inferior”––the corollas attach not to the stem tip below the ovary (as in, say, a tomato flower) but to the top of the ovary itself (as in an apple flower). In white crownbeard, each corolla bears beside it a pappus of two spiky hairs (awns) also attached to the ovary tip. Morphologically, the pappus represents a highly modified calyx and often aids in seed dispersal.

Photo 5: Pubescent involucres are spread open as florets approach anthesis. White pollen tips the anthers at upper-center. Several florets at photo-center have exserted styles. Photo – September 9.
Photo 6: Except for the corollas and sexual parts, all surfaces within the floral clusters have dense puberulence. Ray florets of a flower head open before disk florets. Note structure of involucres. Photo – October 1.

Fertilized disk florets produce flattened, 1-seeded achenes with a notched apex. The slightly ribbed, gray to black fruit has tan marginal wings from pointed base to flat-topped apex and a pappus of 2 awns. Seed dispersal is by wind, animal or flowing water.

Photo 7: Flattened fruits have winged margins and two awns. Photo – October 13.

In a garden, this stout erect plant with its large leaves would add a dramatic flair, and frost flowers would provide interest into the winter months. However, it may aggressively self-seed so that a natural setting may be more appropriate. In a garden, plant numbers can be restrained by removal of fruit before maturity. Flowers are attractive to butterflies and other insects. It is not favored by deer.

Photo 8: Freezing temperatures rupture the epidermis resulting in slowly leaking sap which freezes upon exposure. With subsequent freezing, frost flowers grow from base of stems. Leafy plant to left is Boott’s Goldenrod. Photo – November 24.

White crownbeard is one of five species in the genus that occur in Arkansas. Two other winged species with yellow flowers are yellow wingstem (V. alternifolia) and yellow crownbeard (V. helianthoides). Rayless crownbeard (V. walteri), a winged species of conservation concern, has white composite flowers composed of disk florets only. Cowpen daisy (V. encelioides) has yellow composite flowers, opposite lower leaves and wingless stems. White crownbeard can be identified by its tall, stout stems bearing large leaves along with its white composite flowers that have few ray florets.

Article and photographs by ANPS member Sid Vogelpohl

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