White Wand Beardtongue (Penstemon tubiflorus; also sometimes spelled P. tubaeflorus) of the Plantain (Plantaginaceae) family, formerly of the Figwort (Scrophulariaceae) family, has sparsely leafed, erect stems bearing an elongate inflorescence of white tubular flowers. There is some disagreement on the exact etymology of the genus name. It may be based on words meaning five (“penta”) and stamen (“stemon”) in reference to 5 stamens (4 fertile and one sterile staminode) or based on words meaning nearly/almost (“pen” or “paene”) and thread (“stemon”) possibly in reference to the thread-like staminode which is not a functional stamen. The specific epithet, regardless of spelling, alludes to the tube- or trumpet-shaped flower. It is native to the central U.S. where it is most concentrated in eastern Oklahoma, southeast Kansas, southwest Missouri and a large portion of Arkansas. Outside this area, scattered occurrences are known in surrounding states along with an area from Pennsylvania to Maine where it is considered introduced. In Arkansas, it occurs in the Arkansas Valley, Boston Mountains, Mississippi Valley Loess Plains (Crowley’s Ridge), Ouachita Mountains, and Ozark Highlands Ecoregions, mostly absent from lower portions of the Gulf Coastal and Mississippi Alluvial Plains. Habitats include areas with well-drained soils where full to partial sunlight is available, such as prairies, rights-of-way, open woodlands and woodland margins. Other common names include Tubed Penstemon and Trumpet Penstemon.

This perennial plant has a small caudex supported, during the growing season, by spreading white ropy roots. Individual mature plants have one to several erect flowering stems surrounded by basal leaves. Stems lack branches and grow to 3 feet tall. They die at the end of the growing season but may remain standing into the next growing season. The medium-green stems (lower portion may be purplish in sunny sites) are terete, smooth and glabrous with naked internodes. Diameter of the slender stems, about ¼ inch at their bases, gradually and uniformly decreases to the apex of the inflorescence. Individual plants may be clumped together.

Flowering plants have basal and cauline leaves, while non-flowerig plants have only basal leaves. Some basal leaves, to 4 inches long and ½ inch wide, may remain over winter months with renewed leaf-growth in late winter. Basal leaves vary from obovate to oblong-lanceolate with rounded to bluntly pointed apexes and long-tapered bases. Upper surface is medium green and lower surface is a slightly lighter green; both surfaces are typically glabrous. Margins of the slightly leathery leaves are usually entire but may have minute teeth. Widely spaced secondary pinnate veins extend from the midvein at 45⁰ angles, but gradually curve until they become parallel to leaf margin.

Cauline leaves occur in opposite pairs with 6+ pairs below the inflorescence. Pairs, widely spaced, are rotated one from another at varying degrees. The lowermost spatulate leaves, with long-tapering bases, are smaller than leaves immediately above – – those being to 5 inches long and 2 inches wide. Above the spatulate leaves, oblong-lanceolate leaves are sessile with rounded to slightly cordate to clasping bases and apexes change from rounded to acuminate to acute. Above the oblong-lanceolate leaves, leaf size decreases sharply to the base of the inflorescence where leaves become deltate-ovate. Internode lengths between the opposite pairs increases noticeably such that lower lengths of a mature 32-inch stem may be 1½-2½ inches, while lengths of upper internodes may be 6-8 inches. Leaf color, margins and venation of cauline leaves are about the same as for basal leaves with the blade surface of larger leaves in more favorable sites being undulating to “rumpled”. Within the inflorescence, the opposite bract-like leaves become lanceolate and increasingly small to the point of being minute at the most distal portions of the inflorescence.

Flowers bloom for several weeks in mid-spring. The free-standing terminal inflorescences, from 6-18 inches long and ½-1+ inch wide, are in stout panicles with 4-8 pairs of opposite, strongly ascending cymes. Flowers of a well-formed panicle are arranged with a “primary flower” centered above the panicle’s stalk with a second flower behind the first flower, along with an opposite pair of cymes; one at both sides of the primary flower. A well-formed panicle may have 12+ flowers. When floral internodes are closely spaced, inflorescences tend to have a tight, cylindrical form while inflorescences with more widely spaced internodes tend to have a tiered-cylindrical form. Although variable, often the dense short glandular pubescence covering peduncles (stalks bearing multiple flowers) and pedicels (stalks bearing a single flower – – first flowers to reach anthesis) extends a short way down the main axis (rachis) of the inflorescence. In the inflorescence, the increasingly small leaf-pairs subtend the opposite cyme-pairs to the ultimate cyme at axis apex. The uppermost cyme-pairs, becoming increasingly small, also become increasingly compact as peduncles and pedicels become less stout.

The white tubular flowers (to ¾+ inch long) have a 2-lobed upper lip and a 3-lobed lower lip; lobes are uniformly spreading from a flared throat. All lobes, with rounded apexes, are about the same shape with those of the lower lip being larger and projecting farther. All lobes are smoothly textured and typically lack noticeable nectar guides. Lips unite at the throat to form a smoothly narrowing, funnel shaped tube set in a pale green calyx. The calyx (to 3/16 inch long) consist of 5 ascending, triangular to lanceolate lobes that join to form a very short cup. With calyxes horizontally oriented and the corolla tube descending, faces of flowers are down-cast. Typically, dense short glandular pubescence covers exterior of the corolla and the interior throat – – pubescence often extending onto the calyx. (Flowers may have faint purplish nectar guides and bases of flowers may be slightly purplish.)

Flowers have a pistil (ovary + style + stigma), four fertile stamens (filaments + anthers) and an infertile stamen, referred to as a staminode or the beardtongue. Fertile stamens, adnate to lower side of the corolla tube, occur as a longer pair and a shorter pair, each with 2-lobed dark purple anthers separated across the tips of the white filaments. The paired-filaments, distally following the contours of the throat, curve away from each other and then recurve so that paired-anthers face each other at the mouth. Anthers of the shorter filaments are positioned just below those of the longer filaments; all visible below the upper lip. The white, terete style (⅜ inch long) extends from its slightly widened base to a flat apex topped with the stigmatic surface. The white staminode, adnate to the upper side of the corolla tube, curves down so that it is positioned on the lower lip and extends farther out than the anthers and style. The staminode’s flattened, up-facing distal portion is covered with relatively long, sparse, yellowish hairs. The stigma is well hidden among the stamens with the staminode extending well beyond the anthers. The glabrous, green ovary (less than 1/16 inch long), set within the very small cup, has an onion-shape topped with the style. At anthesis, anther lobes dehisce to release white pollen. Style and filaments are glabrous.

The 2 locular ovaries of fertilized flowers develop into green, tear-drop-shaped hardened capsules that grow to be twice as long as the ⅜ inch calyx. With seed maturity, the entire inflorescence becomes a bronzy-brown and pubescence is lost. Capsules, to 5/16 inch long and 3/16 inch wide with a sharp apex (style remnant), split at their apexes into 2 chambers. Capsules divide near the top part-way down their sides so that the tiny seeds can be shaken out. The irregularly shaped, squarish, angular brown seeds are less than 1/32 inch wide. Stems with capsules still set in their calyxes may persist through the next growth-year, becoming dull brown.

White Wand Beardtongue is an excellent plant for any garden style where conditions are mostly sunny and soils are well-drained. This small, erect perennial is noticeable throughout the growing season and especially showy when the elevated inflorescence bears its pure-white flowers. It provides nectar and pollen to various bees, swallowtails and hummingbirds.

In addition to White Wand Beardtongue, eight other beardtongues occur in Arkansas. Five have white or whitish flowers (some with pinkish or purplish color or more noticeable colored nectar guides): Arkansas Beardtongue (P. arkansanus), Foxglove Beardtongue (P. digitalis), Lowland Beardtongue (P. alluviorum), Nodding Beardtongue (P. laxiflorus) and Pale Beardtongue (P. pallidus). White Wand Beardtongue can be distinguished by its smaller size, an inflorescence that is usually dense above a near-naked upper stem, corollas with similarly shaped flaring lobes (actinomorphic flowers), and corolla lobes that unite to form a smoothly narrowing, funnel-shaped tube. The other three non-white beardtongues in Arkansas are Scarlet Beardtongue (Penstemon murrayanus), Prairie or Showy Beardtongue (Penstemon cobaea), and Sharp-Sepal Beardtongue (Penstemon tenuis).

Article and photographs by ANPS member Sid Vogelpohl

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