Wild Flowers of Pittsburgh

Leguminosae

Black Locust (Robinia pseudoacacia)

Robina-pseudoacacia-2013-05-18-Beechview-01This tree is ubiquitous in southwestern Pennsylvania, so it may come as some surprise to Pittsburghers that we live at the northern end of a native range that is actually very small, mostly in the Appalachians and foothills. The Black Locust has been much planted elsewhere, however, and may easily naturalize itself. It is in many ways an ideal urban tree: it grows fast, tolerates city conditions with no complaints, and has showy clusters of white pea flowers after most of the other flowering trees have stopped blooming. It does, however, have one serious flaw. Mature specimens are brittle, and can easily drop large branches in storms, crushing cars or bringing down power lines. When your power goes out in a thunderstorm, there’s a very good chance you have a Black Locust to blame.

The dangling chains of white pea-shaped flowers are unique among our native trees. Leaves are pinnately compound, with smooth-edged elliptical leaflets. The leaves often turn yellow and begin to drop in August, long before any other trees are even thinking about autumn. Mature trees have rough and shaggy bark, and often show scars of broken branches.

Gray describes the genus and the species (which he spells “Pseudo-Acacia”):

ROBÍNIA L. LOCUST. Calyx short, 5-toothed, slightly 2-lipped. Standard large and rounded, turned back, scarcely longer than the wings and keel. Stamens diadelphous. Pod linear, flat, several-seeded, at length 2-valved. — Trees or shrubs, often with spines for stipules. Leaves odd-pinnate, the ovate or oblong leaflets stipellate. Flowers showy, in hanging axillary racemes. (Named for John Robin, herbalist to Henry IV. of France, and his son Vespasian Robin, who first cultivated the Locust-tree in Europe.)

R. Pseùdo-Acàcia L. (common L., False Acacia.) Branches glabrous or glabrate; racemes slender, loose; flowers white, fragrant; pod smooth.— Along the mts., Pa. to Ga., and in the Ozark Mts. of Mo., Ark., and Okla.; commonly cultivated as an ornamental tree, and for its valuable timber, and naturalized in many places. May, June.


Redbud (Cercis canadensis)

A common tree in the woods around Pittsburgh, and even more common in front yards, where it is a prized ornamental. The tree doesn’t get very tall, but in early spring it covers itself with magenta flowers that light up the forest. If you look at them closely, you can see that each flower is a perfect little pea blossom (although Gray calls it “imperfectly papilionaceous”), showing that this is an arboreal relative of our common beans or sweet peas.

This tree was beginning to bloom in late March in Bird Park, Mount Lebanon.

Gray describes the genus and the species:

CÉRCIS L. REDBUD. JUDAS TREE. Calyx 6 toothed. Corolla imperfectly papilionaceous; standard smaller than tbe wings and inclosed by them in the bud; the keel petals larger and not united. Stamens 10, distinct, declined. Pod oblong, flat, many-seeded, the upper suture with a winged margin. Embryo straight.—Trees, with rounded heart-shaped simple leaves, caducous stipules, and red-purple flowers in umbel-like clusters along the branches of the last or preceding years, appearing before the leaves, acid to the taste. (The ancient name of the oriental Judas Tree.)

C. canadensis L (REDBUD.) Leaves pointed; pods nearly sessile above the calyx.—Rich soil, N. Y.  and N. J. to Fla., w. to s. Ont., e. Neb., and Tex.—A small ornamental tree, often cultivated.


Showy Tick-Trefoil (Desmodium canadense)

Tick-trefoils are mild annoyances to hikers and walkers, but this one is such a beautiful flower that we can easily forgive it. Like all the other tick-trefoils, it has transformed the ordinary legume of the pea family into a fabulously efficient instrument of dispersal. The pod is divided into individual segments that separate easily, and each of them is coated with sticky adhesive hairs. As you pass by the plant, several of those segments stick to your clothes and ride off with you, at least until you notice them. It may be quite a distance: since the seedpods are sticky rather than prickly, you tend not to notice them until you see them.

Other tick-trefoils have pretty but inconspicuous little flowers; this one, however, has larger flowers in a dense and showy raceme. This plant was growing in a hillside clearing in Scott Township, where it was blooming in late July.

Flowers. Pink-purple, in dense branching raceme; the standard slightly paler.

Leaves. Dense on the stem; three leaflets arranged pinnately; lanceolate, entire; rough, especially beneath; on short petioles.

Stem. Somewhat sparse hairs; tough and inflexible.

Gray describes the genus and the species:

DESMÒDIUM Desv. TICK TREFOIL.

Calyx usually 2-lipped. Standard obovate; wings adherent to the straight or straightish and usually truncate keel, by means of a little transverse appendage on each side of the latter. Stamens diadelphous, 9 and 1, or monadelphous below. Pod flat, deeply lobed on the lower margin, separating into flat reticulated joints (mostly roughened with minute hooked hairs). — Perennial herbs, with pinnately 3-foliolate (rarely 1-foliolate) leaves, gtipellate. Flowers in axillary or terminal racemes, often panicled, and 2 or 8 from each bract, purple ol purplish, often turning green in withering. Stipules and bracts scale-like, often striate. (Name from desmos, a bond or chain, from the connected jointe of the pods.) Meibomia Adans.

§ 3. Pod slightly if at all stalked in the calyx; racemes panicled.

Stipules small and inconspicuous, mostly deciduous; pods of few rounitsl or obliquely oval or sometimes roundish-rhomboidal joints 3-6 mm. long.

Stems erect; bracts before flowering conspicuous; racemes densely flowered.

16. D. canadénse (L.) DC. Stem hairy, 6-15 dm. high; leaflets oblonq-lanceolate or ovate-lanceolate, obtuse, with numerous straigbtish veins, much longer than the petiole, 3.7-7.5 сш. long; flowers showy, larger than in any of our other species, 8-12 mm. long. (Meibomia Ktze.) — Open woods and banks of streams, N.B. to N.C., L. Winnipeg, Kan., and Okla.

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In How to Know the Wild Flowers (1920), Mrs. Dana gives us this description:

TICK-TREFOIL.

Desmodium Canadense. Pulse Family.

Stem.—Hairy; three to six feet high. Leaves.—Divided into three somewhat oblong leaflets. Flowers.—Papilionaceous; dull purplish-pink; growing in densely flowered racemes. Pod.—Flat ; deeply lobed on the lower margin; from one to three inches long; roughened with minute hooked hairs by means of which it adheres to animals and clothing.

Great masses of color are made by these flowers in the bogs and rich woods of midsummer. They are effective when seen in the distance, but rather disappointing on closer examination, and will hardly bear gathering or transportation. They are by far the largest and most showy of the genus….

Many of us who do not know these plants by name have uttered various imprecations against their roughened pods. Thoreau writes: ” Though you were running for your life, they would have time to catch and cling to your clothes….These almost invisible nets, as it were, are spread for us, and whole coveys of desmodium and bidens seeds steal transportation out of us. I have found myself often covered, as it were, with an imbricated coat of the brown desmodium seeds or a bristling chevaux-de-frise of beggar-ticks, and had to spend a quarter of an hour or more picking them off in some convenient spot; and so they get just what they wanted—deposited in another place.”

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In her Nature’s Garden (1900), Neltje Blanchan meditates on the ability of such plants as this to disperse themselves far and wide, and gives us the fascinating details of this species’ pollination:

Canadian or Showy Tick-trefoil

(Meibomia Canadensis) Pea family
(Desmodium Canadense of Gray)

Flowers—Pinkish or bluish purple, butterfly-shaped, about 1/2-in. long, borne in dense, terminal, elongated racemes. Stem: Erect, hairy, leafy, 2 to 8 ft. high. Leaves: Compounded of 3 oblong leaflets, the central one largest; upper leaves nearly seated on stem; bracts, conspicuous before flowering, early falling off. Fruit: A flat pod, about 1 in. long, jointed, and covered with minute hooked bristles, the lower edge of pod scalloped; almost seated in calyx. Preferred Habitat—Thickets, woods, river banks, bogs. Flowering Season—July—September. Distribution—New Brunswick to Northwest Territory, south to North Carolina, westward to Indian Territory and Dakota.

As one travels hundreds or even thousands of miles in a comfortable railway carriage and sees the same flowers growing throughout the length and breadth of the area, one cannot but wonder how ever the plants manage to make the journey. We know some creep along the ground, or under it, a tortoise pace, but a winning one; that some send their offspring flying away from home, like dandelions and thistles; and many others with wings and darts are blown by the wind. Berries have their seeds dropped afar by birds. Aquatic plants and those that grow beside running water travel by river and flood. European species reach our shores among the ballast. Darwin raised over sixty wild plants from seed carried in a pellet of mud taken from the leg of a partridge. So on and so on. The imagination delights to picture these floral vagabonds, each with its own clever method of getting a fresh start in the world. But by none of these methods just mentioned do the tick-trefoils spread abroad. Theirs is indeed a by hook or by crook system. The scalloped, jointed pod, where the seeds lie concealed, has minute crooked bristles, which catch in the clothing of man or beast, so that every herd of sheep, every dog, every man, woman, or child who passes through a patch of trefoils gives them a lift. After a walk through the woods and lanes of late summer and autumn, one’s clothes reveal scores of tramps that have stolen a ride in the hope of being picked off and dropped amid better conditions in which to rear a family.

Only the largest bees can easily “explode” the showy ticktrefoil. A humblebee alights upon a flower, thrusts his head under the base of the standard petal, and forces apart the wing petnls with his legs, in order to dislodge them from the standard, his motion causes the keel, also connected with the standard, to snap down violently, thus releasing the column within and sending upward an explosion of pollen on the under surface of the bee. Here we see the wing petals acting as triggers to discharge the flower. Depress them and up flies the fertilizing dust—once. The little gun will not “go off” twice. No nectar rewards the visitor, which usually is a pollen-collecting bee. The highly intelligent and important humblebee has tne advantage over his smaller kin in being able to discharge the pollen from both large and smaller flowers.


Yellow Sweet Clover (Melilotus officinalis)

Hard to tell from White Sweet Clover (M. alba) until they both bloom. When they do bloom, the yellow species reveals sloppier habits; the flower spikes are more ragged than the ones of M. alba, with withering flowers retained for a long time. Nevertheless, the delightful scent is enough to make us forget the slight slovenliness of the presentation. Yellow Sweet Clover grows plentifully along roadsides, and is often one of the first plants to colonize a recently disturbed site; this plant was growing in a park in Beechview where the earth had just been replaced after the building of a new playground. It was blooming in the middle of July.

Gray describes the genus and the species (and has anyone in history other than Asa Gray ever used the English word “melilot”?)

MELILÒTUS [Tourn.] Hill. MELILOT. SWEET CLOVER. Flowers much as in Trifolium, but in spike-like racemes, small. Corolla deciduous, free from the stamen-tube. Pod ovoid, coriaceous, wrinkled, longer than the calyx, scarcely dehiscent, 1-2-seeded. — Annual or biennial herbs, fragrant in drying, with pinnately 3-foliolate leaves. (Name from meli, honey, and lotos, some leguminous plant.)

M. officinalis (L.) Lam. (YELLOW M.) Upright, usually tall; leaflets obovate-oblong, obtuse, closely serrate; petals yellow, of nearly equal length. 6-9 mm. long; pod 2.5-3.5 mm. long, glabrous or glabrate, prominently cross-ribbed. — Waste or cultivated ground, common. (Nat. from Eu.)


Cow Vetch (Vicia cracca)

A European import cultivated for fodder, Cow Vetch tends to be found wherever livestock is nearby. The vines twine through other less decorative weeds, and the beautiful blue-purple flowers light up the edges of fields. This patch grew in a sunny meadow near Cranberry, where it was blooming in the middle of June.

Gray describes the genus and the species:

VICIA [Tourn.] L. VETCH. TARE

Calyx 5-cleft or 5-toothed, the 2 upper teeth often shorter, or the lowest longer. Wings of the corolla adhering to the middle of the keel. Stamens more or less diadelphous (9 and 1); the orifice of the tube oblique. Style filiform, hairy all round or only on the back at the apex. Pod flat, 2-valved, 2-several-seeded. Seeds globular. Cotyledons very thick, remaining under ground in germination. Herbs, mostly climbing more or less by the tendril at the end of the pinnate leaves. Stipules half-sagittate. Flowers or peduncles axillary. (The classical Latin name.)

V. cracca L. Appressed-pubescent; leaflets 8-24, oblong-lanceolate, strongly mucronate; racemes densely many-flowered, 1-sided; flowers blue, turning purple (rarely white), 1-1.2 cm. long, reflexed; calyx-teeth shorter than the tube. Borders of thickets or in fields, Nfd. to N. J., w. to Ky., la., and Minn. June- Aug. (Eu.)


Alsike Clover (Trifolium hybridum)

Red Clover (T. pratense) is more common and very similar, and grows in most of the same places. The best way to tell the difference is by the leaves, which in Red Clover usually (but not always) show a chevron pattern but are unmarked in Alsike Clover; and by the color of the flowers, which in Alsike Clover is less magenta and more pale rosy pink, with young white flowers in the center of the head. In fact, it does look like something halfway between Red Clover and White Clover (T. repens), which may account for the specific name hybridus for a plant that is not a hybrid.

This plant grew in a meadow near Cranberry, where it was blooming in the middle of June.

Gray describes the genus and the species:

TRIFOLIUM [Tourn.] L. CLOVER. TREFOIL

Calyx persistent, 5-cleft, the teeth usually bristle-form. Corolla mostly withering or persistent; the claws of all the petals, or of all except the oblong or ovate standard, more or less united below with the stamen-tube; keel short and obtuse. Tenth stamen more or less separate. Pods small and membranous, often included in the calyx, 1-6-seeded, indehiscent, or opening by one of the sutures. Tufted or diffuse herbs. Leaves mostly palmately (sometimes pinnately) 3-foliolate; leaflets usually toothed. Stipules united with the petiole. Flowers in heads or spikes. (Name from tres, three, and folium, a leaf.)

T. HYBRIDUM L. (ALSIKE C.) Resembling T. repens, but the stems erect or ascending, not rooting at the nodes; leaflets ovate, rounded at apex; flowers rose-tinted. Generally common. (Introd. from Eu.)


Everlasting Pea (Lathyrus latifolius)

Everlasting Pea is a vigorous vine that can take over whole hillsides. It compensates us for the space it takes with a glorious array of flowers in shades from white through deep magenta, often (as here) with stripes or bicolor patterns.

Gray describes the genus and the species:

LATHYRUS [Tourn.] L. VETCHLING. EVERLASTING PEA

Style dilated and flattish (not grooved) above, hairy along the inner side (next the free stamen). Sheath of the filaments scarcely oblique at the apex. Otherwise nearly as in Vicia. Our species perennial and mostly smooth plants. (Lathyros, a leguminous plant of Theophrastus.)

L. latifolius L. (EVERLASTING or PERENNIAL PEA.) Tall perennial with broadly winged stems; leaves and stipules coriaceous and veiny; petioles mostly winged; the 2 elliptic to lanceolate leaflets 0.5-1 dm. long; peduncles stiff, many-flowered; flowers showy, pink, purple, or white. Frequently cultivated, and escaping to roadsides and thickets, Ct. to 1). C. (Introd. from Eu.)

Another picture is here.


Red Clover (Trifolium pratense)

This ubiquitous European import grows almost anywhere the grass isn’t mowed too frequently. It keeps blooming throughout the season: this flower was going strong in early November in Beechview. It came to America as a pasture crop, and soon found that it really liked our open spaces.

Gray describes the genus and the species:

TRIFOLIUM [Tourn.] L. CLOVER. TREFOIL
Calyx persistent, 5-cleft, the teeth usually bristle-form. Corolla mostly withering or persistent; the claws of all the petals, or of all except the oblong or ovate standard, more or less united below with the stamen-tube; keel short and obtuse. Tenth stamen more or less separate. Pods small and membranous, often included in the calyx, 1-6-seeded, indehiscent, or opening by one of the sutures. Tufted or diffuse herbs. Leaves mostly palmately (sometimes pinnately) 3-foliolate; leaflets usually toothed. Stipules united with the petiole. Flowers in heads or spikes. (Name from tres, three, and folium, a leaf.)

T. PRATENSE L. (RED C.) Perennial; stems ascending, somewhat hairy; leaflets oval or obovate, often notched at the end and marked on the upper side with a pale spot; stipules broad, bristle-pointed; heads ovoid, sessile or not rarely pedunculate; corolla magenta to whitish; calyx soft-hairy. Fields and meadows; extensively cultivated. (Introd. from Eu.)


White Sweet Clover (Melilotus albus)

The height of its season is the late spring and early summer, but don’t count White Sweet Clover out at any season. This plant was sticking its head through a chain-link fence in Beechview in early November. Imported for fodder, White Sweet Clover and the similar yellow species M. officinalis (almost indistinguishable until the flowers appear) have made themselves at home here to such an extent that some regard them as pests. Nevertheless, as nitrogen-fixers that cattle like to eat, they give us a lot in return for the inconvenience they cause us.

Gray takes Melilotus as feminine, though modern botanists have conspired to claim the name for the masculine side. He describes the genus and species:

MELILOTUS [Tourn.] Hill. MELILOT. SWEET CLOVER.
Flowers much as in Trifolium, but in spike-like racemes, small. Corolla deciduous, free from the stamen-tube. Pod ovoid, coriaceous, wrinkled, longer than the calyx, scarcely dehiscent, 1-2-seeded. Annual or biennial herbs, fragrant in drying, with pinnately 3-foliolate leaves. (Name from meli, honey, and lotos, some leguminous plant.)

M. ALBA Desr. (WHITE M.) Tall; leaflets narrowly obovate to oblong, serrate, truncate or emarginate ; corolla white, 4-5 mm. long, the standard longer than the other petals pod 3-4 mm. long, somewhat reticulate. Rich soil, roadsides, etc., common. (Nat. from Eu.)


Hog Peanut (Amphicarpaea bracteata)

Amphicarpaea-bracteata-2009-08-22-Mt-Lebanon-01

A vine that twines its way through the underbrush along creeks and streams, dangling clusters of flowers in white, pink, or purple. These flowers produce seeds, but the vine also grows less showy flowers near the ground that turn into a single underground seed, like a peanut. This vine was found in Bird Park in Mount Lebanon.

Gray describes the genus (listed as Amphicarpa) and species (listed as A. monoica):

AMPHICARPA Ell. HOG PEANUT
Flowers of 2 (or 3) kinds; those of the racemes from the upper branches perfect; those near the base and on filiform creeping branches with the corolla none or rudimentary, and few free stamens, but fruitful; reduced flowers of slightly different form sometimes also on aerial racemes. Calyx about equally 4 (rarely 5)-toothed. Stamens diadelphous. Pods of the upper flowers, when formed, somewhat scimiter-shaped, stipitate, 3-4-seeded; of the lower ones commonly subterranean and fleshy, obovate or pear-shaped, ripening usually but one large seed. Low and slender perennials; the twining stems clothed with brownish hairs. Leaves pinnately 3-foliolate; leaflets rhombic-ovate, stipellate. Petals purplish. Bracts persistent, round, partly clasping, striate. as well as the stipules. (Name from amphi, both, and karpos, fruit, in allusion to the two kinds of pods.) FALCATA Gmel.

A. monoica (L.) Ell. Leaflets thin, 1.3-5 cm. long; racemes nodding; calyx of the upper flowers 4 mm. long; the ovary glabrous except the mostly appressed hairy margin; pod 2.5 cm. long; ovary and pod of the rudimentary flowers hairy. (Falcata comosa Am. auth.; Glycine comosa L. ?) Rich damp woodlands, common. Aug., Sept.


Everlasting Pea (Lathyrus latifolius)

Lathyrus-latifolius-2009-09-30-02

Sometimes called Perennial Sweet Pea. These weedy vines cover hillsides in residential neighborhoods, often where they had been planted generations before. Once you have Everlasting Peas, you have them forever. But is that such a bad thing?

From Gray’s Manual of Botany: L. latifolius L. (EVERLASTING or PERENNIAL PEA.) Tall perennial with broadly winged stems; leaves and stipules coriaceous and veiny; petioles mostly winged; the 2 elliptic to lanceolate leaflets 0.5-1 dm. long; peduncles stiff, many-flowered; flowers showy, pink, purple, or white. Frequently cultivated, and escaping to roadsides and thickets, Ct. to D. C. (Introd. from Eu.)

(This was from the 1908 edition. The 1890 edition does not list Lathyrus latifolius, suggesting that it had not yet become established as a frequent escape.)


Crown Vetch (Securigera varia)

2009-09-13-Securigera-varia-01

Wherever there are hillsides that no one wants to mow, there is crown vetch. Its cheerful vigor means that it often escapes and invades a hillside on its own, but its happy clover-like pink flower heads make us willing to forgive its bad manners.


White Clover (Trifolium repens)

2009-09-12-Trifolium-repens-01

You see it everywhere, but do you ever stop to look at it close up? This is your chance. Take a moment to contemplate the beauty of white clover in an ordinary lawn.


Birdfoot Trefoil (Lotus corniculatus)

Lotus-corniculatus-01

The bright, pure yellow of these ubiquitous roadside flowers is hard to equal. Close up, the perfect little pea flowers reveal contrasting red stripes.


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