Wild Flowers of Pittsburgh

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Pittsburgh Palm (Ailanthus altissima)

Obviously this is not known as “Pittsburgh Palm” in other cities, but here the name is common. Elsewhere it is known as Tree of Heaven, Chinese Sumac, Stinking Sumac, Stink Tree, Ghetto Palm, and—because of its aggressive invasiveness—Tree from Hell. It grows everywhere, whether you like it or not; it can pop up in the chimney of an old house or in the crack of a sidewalk.

Nevertheless, it came to this country as a prized ornamental tree, and the female trees (the species is dioecious, meaning that the male and female flowers are on separate plants) are striking in midsummer when they are topped with tufts of red seeds.

This tree was growing beside the bicycle ramp to the Herr’s Island Railroad Bridge, which conveniently allowed us to photograph the top of it.

Gray describes the genus and the species, which he calls A. glandulosa (there are more than a dozen botanical synonyms for this plant):

AILÁNTHUS Desf. TREE OF HEAVEN. Flowers polygamous. Calyx regular, 5-parted, the lobes imbricated. Petals 5, infolded-valvate. Stamens in staminate flowers 10, in perfect flowers 2-3, in pistillate flowers none. Disk lobed. Ovary 2-5-parted, becoming in fruit 1-5 narrowly oblong membranaceous samaras (1-seeded in the middle). — Handsome trees of rapid growth. Leaves odd-pinnate. Flowers small, green or yellowish, in ample terminal panicles, especially the staminate of unpleasant odor. (Name said to be from a vernacular Moluccan designation, meaning tree of heaven, in allusion to the height in the native habitat.)

A. glandulosa Desf. Leaves 3-6 dm. long, 11-23-foliolate; leaflets ovate, acuminate, entire or sparingly toothed toward the base. — Extensively cultivated as a shade tree, freely spreading by suckers, and locally self-sown. (Introd. from Asia.)

Rhododendron (Rhododendron maximum)

Big bushes with large, leathery evergreen leaves and ball-like clusters of white or pinkish flowers, these ancestors of garden Rhododendrons are unmistakable. The only thing that resembles them at all is the Mountain Laurel, whose leaves and flowers are much smaller.

The flowers are white, often blushed with pink, especially when they are young. The upper petal is marked with greenish-yellow spots.

Rhododendron can grow in deep shade, although it seems to bloom more prolifically in the sun. These were growing in the woods along the Trillium Trail in Fox Chapel, where they were blooming at the end of June.

Gray describes the genus and the species, which he places in the Eurhododendron or Rhododendron-proper section of the genus.

RHODODÉNDRON L. Calyx mostly small or minute. Stamens sometimes as few as the corolla-lobes, more commonly twice as many, usually declined; anther-cells opening by a round terminal pore. Capsule 5-celled, 5-valved, many-seeded. Seeds scale-like.— Shrubs or small trees, of diverse habit and character, with chiefly alternate entire leaves, and large and showy flowers in umbeled clusters from terminal buds. (Rhododendron, rose-tree; the ancient name.)

EURHODODÉNDRON DC. Leaves coriaceous and persistent; stamens (commonly 10) and style rarely exserted, somewhat declined, or sometimes equally spreading.

R. máximum L. (GREAT LAUREL.) Shrub or tree, 2-10 m. high; leaves 0.8-2 dm. long, very thick, elliptical-oblong, or lance-oblong, acute, narrowed toward the base, very smooth, with somewhat revolute margins; pedicels viscid, corolla bell-shaped, 3.5-5 cm. broad, pale rose-color or nearly white, greenish in the throat on the upper side, and spotted with yellow or reddish. — Damp deep woods, rare from N. S., Me., and Que. to Ont. and O., but very common through the Alleghenies from N. Y. to Ga. June, July.

Common Milkweed (Asclepias syriaca)

This distinctively odd-looking plant is a common sight along the road or at the edges of fields; this one grew at the edge of the woods in Mount Lebanon, where it was blooming in late June. The plants stand straight and tall; the flowers form umbels in almost perfect spheres. From a distance their color resembles the color that used to be called “flesh” in children’s crayon boxes. The heady scent of Milkweed blossoms attracts butterflies and bees, but also—as we see in the picture above—legions of little ants.

Milkweeds and their allies were traditionally placed in the Milkweed family, Asclepiaceae; but modern botanists make that family a subfamily (Asclepiadoideae) of the Dogbane family, Apocynaceae. The species name syriaca comes from a pre-Linnaean botanist who confused this species with one from the Near East.

Gray describes the genus and the species:

ASCLEPIAS [Tourn.] L. MILKWEED. SILKWEED. Calyx persistent; divisions small, reflexed. Corolla deeply 5-parted; divisions valvate in bud, deciduous. Crown of 5 hooded bodies seated on the tube of stamens, each containing an incurved horn. Stamens 5, inserted on the base of the corolla; filaments united into a tube which incloses the pistil; anthers adherent to the stigma, each with 2 vertical cells, tipped with a membranaeeons appendage, each cell containing a flattened pear-shaped and waxy pollen-mass; the two contiguous pollen-masses of adjacent anthers, forming pairs which hang by a slender prolongation of their summits from 5 cloven glands that grow on the angles of the stigma (extricated from the cells by insects, and directing copious pollen-tubes into the point where the stigma joins the apex of the style). Ovaries 2, tapering into very short styles; the large depressed 5-angled fleshy stigmatic disk common to the two. Follicles 2, one of them often abortive, soft, ovoid or lanceolate. Seeds anatropous, flat, margined, bearing a tuft of long silky hairs (coma) at the hilum, downwardly imbricated all over the large placenta, which separates from the suture at maturity. Embryo large, with broad foliaceous cotyledons in thin albumen. Perennial herbs; peduncles terminal or lateral and between the usually opposite petioles, bearing simple many-flowered umbels, in summer. (The Greek name of Aesculapius, to whom the genus is dedicated.)

A. syriaca L. (COMMON M. or SILKWEED.) Stem tall and stout, finely soft-pubescent; leaves lance-oblong to broadly oval, 1-2 dm. long, pale, minutely downy beneath, as well as the peduncles, etc.; corolla-lobes dull purple to white, 6-9 mm. long; hoods rather longer than the anthers, ovate, obtuse, with a tooth each side of the short stout claw-like horn. (A. Cornuti Dene.) Rich ground, N. B. to Sask., and southw. June-Aug. Intermediates, perhaps of hybrid origin, occur between this and some of the related species.


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