Article and photographs by ANPS member Sid Vogelpohl
St. Andrew’s-cross (Hypericum hypericoides subsp. hypericoides) of the St. John’s-wort (Hypericaceae) family is a small perennial shrub (subshrub) with fine leaves on straight twigs, 4-petal yellow flowers and 2 prominent sepals. Genus name is based on Greek words for “above” and “picture”, from the practice of placing flowers above a wall-mounted picture to discourage evil spirits on St. John’s feast day. Specific epithet translates to “hypericum resembling hypericum”*. Common name refers to the arrangement of flower petals resembling the cross of “Saint Andrew the Apostle”. Occurrence in the US extends from eastern Texas and eastern Oklahoma, across southern Missouri, eastward to the Atlantic coast, thence following the Atlantic and Gulf coasts back to Texas. In Arkansas, occurrence is statewide except for northern portions of the Ozark Plateaus and counties boarding the Mississippi River. Habitats include sandy to rocky sites with mesic to dry soils; such as, sunny glades, open upland-woodlands and woodland borders.
The drought-tolerant shrub has deep, branching taproots along with descending fibrous roots. The short-lived plants, with branches to 3 feet long, have a main stem off the rootstock or a few to multiple ascending branches from the base with frequent branching distally. Young plants tend to be mound-like with dense foliage while older plants often become decumbent. Lower portion of branches become leggy to scraggly as lower small branches are shed. Main stem, branches and twigs (current year’s growth) are reddish brown with the thin bark exfoliating to expose inner smooth bark. Plants are evergreen to tardily deciduous (see Photo 4). The terete (round in cross-section) branches are brittle. Entire plant is glabrous (without hairs). Leaf pairs are decussate (rotated 90⁰).
Current year’s twigs are referred to, herein, as “primary” or “secondary”. Primary twigs grow from terminal buds of previous year’s non-flowering twigs and from scattered lateral buds of previous year’s flowering and non-flowering twigs. Secondary twigs grow from leaf axils of primary twigs. Primary and secondary twigs initially have pale green bark which becomes reddish brown early in the growth-year. The wiry primary twigs have a final length from less than an inch to 10 inches with base-width of longest twigs to ⅛ inch. Secondary twigs, set at about 45⁰ off primary twigs, are from near-0 to 2 inches long (usually <1 inch) with a base-width less than half that of primary twigs. Secondary twigs are thread-like and flexible. Twigs have thin, flexible wings that extend down from leaf base to a point between the next lower pair of leaves – wings do not connect.
Twigs have opposite pairs of narrowly oblong to oblanceolate leaves that are uniformly spaced along a twig and separated by about ¼ to ¾ inches. Opposite leaf pairs have the same size across twig rachises. Prior to development of secondary twigs, primary twigs have a leafy, columnar appearance. Lower leaves of primary twigs often subtend a cluster (fascicle) of leaves while upper leaves subtend secondary twigs some of which bear flowers. Primary twigs may have up to a dozen leaf pairs while secondary twigs may have 1-4 pairs. Twigs (primary or secondary) that do not bear flowers, terminate with a final pair of leaves centered by a tiny, elongate apical bud which extends twig-length in the following growth-year. Twigs that had flowers in the previous growth-year produce new twigs below that inflorescence (now dead) so that flowering branches broaden year-by-year.
Leaves of primary twigs grow to about an inch long and ⅓ wide and are about twice the size of similarly shaped leaves of secondary twigs. Leaves are slightly broader at or above mid-leaf and have obtuse to rounded apices and rounded to wedge-shaped bases. The simple leaves, with pale green upper surface and green to pale bluish-green lower surface, have entire (uncut) and narrowly recurved margins. The sessile (lacking stalks) leaves may exhibit glandular dots (punctate leaves) that are more noticeable on the abaxial leaf surface. Pinnate venation is obscure above and below with the well-defined midrib recessed slightly above and expressed below. Shrubs are evergreen to tardily deciduous.
The inflorescence, present July into August, mostly consists of 3-flower-clusters with a central flower and a pair of lateral, axillary flowers. All 3 flowers are terminal on a primary or secondary twig with the lateral flowers subtended by the uppermost leaf pair (see Photo 14). Alternatively, a central flower may occur with the uppermost leaf pair subtending twigs (see Photo 15). With 3-flower clusters, the central flower blooms first and both lateral flowers bloom simultaneously shortly thereafter. Lower on a twig, only one leaf of a leaf pair may subtend a flower. Flowers are held erect on short (to ⅜-inch), thread-like pedicels (flower stalks). Flowers are at anthesis for one day. During the flowering period, flowers are loosely scattered across a plant.
A matched pair of broad, spade-shaped sepals are lightly pressed together through the entire bud-to-fruit cycle. The green sepals are sessile, thick and flat. Mature sepals, about 5/16 inch long and ¼ inch wide, are all about the same size and are more prominent than the relatively fine leaves. A matched pair of tiny lanceolate floral bracts (1/16 inch by 1/32 inch), with a broadened base, occur on the pedicel near the sepals. In bud, the folded petals have an elongate-conic shape with only bud-tip showing the day before anthesis. Sepals and pedicels are ascending. Floral bracts are also the same green color as leaves. The smooth sepal margins may be reddish. The paired floral bracts are decussate to the uppermost leaf pair and to the sepal pair.
The 4-petal flowers have to 30+ stamens (filaments + anthers) evenly encircling a prominent 2-locular, superior ovary. Stamens have wispy, greenish yellow filaments that are tipped with 2-lobed, knobby yellow anthers producing yellow pollen. The elongate-conic ovary, at anthesis, is about 3/16 inch tall and < ⅛ inch wide with a narrowed base. Tips of the yellowish green ovaries consist of a partly fused pair of very short, conic pistils (style + stigma). The rather flimsy, irregularly shaped petals are oblong-elliptic to oblanceolate with rounded apices that may have an off-set pointed tip. With petals in an x-configuration, sepals are positioned between the pair of petals that are closer together (see Photo 12).
Fertilized ovaries develop into thick, flattened capsules that remain held between the sepals. Dry capsules are about ⅜ inch long and ¼ inch wide. Capsules dehisce across remnants of the style/stigma and half-way down the capsule’s side-margins. At maturity, the numerous black seed, with low-gloss and finely roughened, are cylindric-oblong with rounded ends. The erect capsules and sepals persist into the next growth-year and often still contain seeds. Seeds (< 1/16 inch long) are probably dispersed by strong wind, surface run-off and small mammals.
St. Andrew’s-cross is adaptable to a sunny to partially sunny home garden with sandy to rocky soils. Its fine foliage, interesting flowers and frequent upper branching would contrast well with larger-leaved native plants when in uncrowded spaces. It is especially well-suited for rock gardens. Older plants tend to become leggy to scraggly and may need pruning. Best natural germination seems to be in areas with exposed rocky soil. A larger, shrubby species of the genus is Shrubby St. John’s-wort which is well-suited for various garden styles.
Nineteen additional species of Hypericum are known to occur in Arkansas most of which have yellow flowers. The St. Andrew’s-cross discussed above is technically Hypericum hypericoides subsp. hypericoides. Another subspecies of St. Andrew’s-cross [Hypericum hypericoides subsp. multicaule (aka Hypericum stragulatum)] also occurs in Arkansas. It is a low-growing, basally much-branched, mat-forming plant to 10 inches tall with slightly woody branches and wider leaves.
- Original name of this species, assigned by Linnaeaus, was Ascyrum hypericoides meaning “Ascyrum resembling hypericum”. When Ascyrum hypericoides was moved to the Hypericum genus, based on procedural rules, name became Hypericum hypericoides meaning “Hypericum resembling hypericum”.
