Wild Flowers of Pittsburgh

Adoxaceae

Highbush Cranberry (Viburnum trilobum)

Not really a cranberry, but it has berries that can be a good substitute for cranberries. The leaves are much like the leaves of Red Maple (Acer rubrum), and the flowers come in dense cymes. Most of the flowers are tiny, but the outer flowers in each cyme, which are sterile, are immensely overgrown, making the whole cyme much more showy and a much more attractive target for pollinators. This bush was growing at the edge of the woods in Harmarville, where it was blooming in late May.

This species is often considered as variety americanum of the Eurasian species V. opulus, and so Gray classifies it:

VIBÚRNUM [Tourn.] L. ARROW-WOOD, LAURESTINUS. Calyx 5-toothed. Corolla spreading, deeply 5-lobed. Stamens 5. Stigmas 1-3. Fruit a 1-celled 1-seeded drupe, with soft pulp and a thin-crustaceous (flattened or tumid) stone. —Shrubs, with simple leaves, and white (rarely pink) flowers in flat compound cymes. Petioles sometimes bearing little appendages which are evidently stipules. Leaf-buds naked, or with a pair of scales. (The classical Latin name, of unknown meaning.)

§ 2. ÓPULUS [T onrn.] DC. Winter-buds scaly; leaves palmately veined and lobed; drupe bright red, acid, globose; stone very flat, orbicular, not sulcate.

V. Ópulus L., var. americànum (Mill.) Ait. (CRANBERRY-TREE, HIGH-BUSH CRANBERRY, PIMBINA.) Nearly smooth, upright, 1-4 m. high; leaves 3-5-ribbed, strongly 3-lobed, broadly wedge-shaped or truncate at base, the spreading lobes pointed, mostly toothed on the sides, entire in the sinuses; petioles bearing 2 glands at the apex; cyme broad, the marginal flowers neutral, with greatly enlarged flat corollas; stamens elongate. (V. americanum Mill.) — In woods and along streams, Nfd. and e. Que. to B. C, s. to N. J., Pa., Mich., Wisc., and n. e. Ia. June, July. (E. Asia.) — The acid fruit of this and the next is a substitute for cranberries. The well-known Snow-ball Tree, or Guelder Rose, is a cultivated state of the typical Old World form, with the whole cyme turned into showy sterile flowers.

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Southern Arrowwood (Viburnum dentatum)

One of several Viburnum species found in our area; this one is not recorded in the literature as occurring in Allegheny County, though it is known to occur in neighboring Butler County. (Shafer’s Preliminary List of the Vascular Flora of Allegheny County, Pennsylvania, lists it as a possible resident, on the grounds that it occurs in neighboring areas.) Nevertheless, these bushes seem to be Viburnum dentatum, and they did grow in Allegheny County, near the edge of the woods on the grounds of Harmarville Rehabilitation Hospital. (We’d be delighted to be corrected in this identification if it’s wrong.) The one above was blooming in early June; the one below in late May. The similar Viburnum recognitum, which may also grow in our area, is sometimes classified as a variety of Viburnum dentatum.

Gray describes the genus and the species, which he places in the Euviburnum or Viburnum-proper section of the genus:

VIBÚRNUM [Tourn.] L. ARROW-WOOD, LAURESTINUS. Calyx 5-toothed. Corolla spreading, deeply 5-lobed. Stamens 5. Stigmas 1-3. Fruit a 1-celled 1-seeded drupe, with soft pulp and a thin-crustaceous (flattened or tumid) stone. —Shrubs, with simple leaves, and white (rarely pink) flowers in flat compound cymes. Petioles sometimes bearing little appendages which are evidently stipules. Leaf-buds naked, or with a pair of scales. (The classical Latin name, of unknown meaning.)

§ 3. EUVIBÚRNUM Koehne (restricted). Winter-buds scaly; leaves pinnately veined (except in V. acerifolium), the veins straightish and terminating in coarse teeth; cymes never radiant, peduncled; drupes blue to black; stone usually grooved.

Leaves cordate or subcordate at base, coarsely toothed, prominently pinnate-veined.

Stone very deeply sulcate ventrally; leaves rather slender-petioled.

V. dentàtum L. (ARROW-WOOD.) Smooth, 1-4.5 m. high, with ash-colored bark; leaves broadly ovate, glabrous, or with hairy tufts in the axils beneath, very numerously sharp-toothed and strongly veined, 5-8 cm. long; fruit globose-ovoid, 6 mm. long; cross-section of stone between kidney- and horseshoe-shaped. — Wet places, N. B. to n. Ga., w. to w. N. Y. and s. Ont. June, July.