Obviously this is not known as Pittsburgh Pest everywhere in its nearly global range, but the name seems to be well established here. It has many other names in English, including the delightful folk etymology “Gallant Soldiers.” It comes originally from South America, where it is a popular ingredient in Colombian cuisine.
The flowers are like tiny five-rayed daisies; the plant is low and hairy,and can grow from any crack in the pavement. This one grew at the edge of a sidewalk in Greenfield, where it was blooming in the middle of July. It is very much an urban weed, ubiquitous in the city of Pittsburgh, but much rarer in the near suburbs, and unknown in all the other counties of the metropolitan area but one (Washington County).
Gray describes the genus and the species:
GALINSÒGA R. & P. Heads several-flowered, radiate; rays 4-6, small, roundish, pistillate. Involucre of 4-5 ovate thin bracts. Receptacle conical, with narrow chaff. Pappus of small oblong cut-fringed chaffy scales, sometimes wanting. — Annual herbs, with opposite triple-nerved thin leaves, and small heads; disk yellow; rays white or reddish. (Named for Dr. Mariano Martinez de Galinsoga, a Spanish botanist.)
Rays white; pappus of disk-flowers about equaling the achenes.
G. parviflòra Cav. Pubescence subappressed; leaves ovate, crenate-serrate, petioled; pappus of the disk-flowers of spatulate obtusish scales.— Roadsides and waste places, from N. E. across the continent. (Adv. from Trop. Am.) Var. Híspida PC. Pubescence more copious, not appressed; pappus-scales of the disk-flowers attenuate and bristle-tipped. — Me. to Ont., Wise., and southw. (Nat. from Trop. Am.)
Golden Ragworts are attractive flowers, a bit like a yellow aster, that bloom in the middle spring, just after the tulips in your garden. The heart-shaped basal leaves and the pinnately lobed (rather fern-like) stem leaves are distinctive. They like a somewhat shady location; these were blooming in early May near a stream in Scott Township.
Gray (with help from J. M. Greenman) describes the genus and the species:
SENECIO [Tourn.] L. GROUNDSEL. RAGWORT. SQUAW-WEED. Revised By J. M. Greenman. Heads many-flowered; rays pistillate or none; involucre cylindrical to bell-shaped, simple or with a few bractlets at the base, the bracts erect-connivent. Receptacle flat, naked. Pappus of numerous very soft and capillary bristles.— Ours herbs, with alternate leaves and solitary or eorymbed heads. Flowers chiefly yellow. (Name from senex, an old man, alluding to the hoariness of many species, or to the white hairs of the pappus.)
S. aureus L. (GOLDEN R. ) Stems erect from rather slender rootstocks, 3-8 dm. high, at first often lightly floccose-tomentose, soon glabrate; lower leaves long-petioled, ovate-rotund to slightly oblong, 1.5-8 cm. long, two thirds as broad, crenate-dentate; stem-leaves lyrate to laciniate-pinnatifid; the uppermost sessile, amplexicaul, often bract-like; inflorescence cymose-corymbose; heads radiate; rays yellow; achenes glabrous. — In wet meadows, moist thickets, and swamps, Nfd., s. to Va., w. to Wisc., Mo., and Ark. May-Aug.
One of our earliest spring flowers, Coltsfoot bursts through the leaf litter in March and soon covers woodsy roadside banks with sunny yellow flowers. These flowers were blooming at the end of March beside the lower parking area at Bird Park in Mount Lebanon.
Gray describes the genus and the species:
TUSSILÀGO [Tourn.] L. COLTSFOOT. Head many-flowered; ray-flowers in several rows, narrowly ligulate, pistillate, fertile; disk-flowers with undivided style, sterile. Involucre nearly simple. Receptacle flat. Achenes slender-cylindric or prismatic; pappus copious, soft, and capillary. — Low perennial, with horizontal creeping rootstocks, sending up scaly scapes in early spring, bearing a single head, and producing rounded heart-shaped angled or toothed leaves later in the season, woolly when young. Flowers yellow. (Name from tussis, a cough, for which the plant is a reputed remedy.)
T. farfara L. — Wet places and along brooks, e. Que. to Pa., O.,and Minn. (Nat. from Eu.)
A charming flower, often cultivated. It likes a moist and somewhat shady location; these plants were blooming in Bird Park in Mount Lebanon at the beginning of September.
The genus Conoclinium was formerly included in Eupatorium, but was separated when Eupatorium was forced to sell off its superfluous species at fire-sale prices.
It is very difficult for a cheap digital camera to capture the delicate blue color of these flowers. The noticeable difference in color between the two pictures is mostly a figment of the camera’s imagination.
Gray describes the genus Eupatorium, the section Conoclinium (now regarded as a separate genus), and the species:
EUPATÒRIUM [Tourn.] L. THOROUGHWORT. Heads discoid, 3-many-flowered; flowers perfect. Involucre cylindrical or bell-shaped, of more than 4 bracts. Receptacle flat or conical, naked. Corolla 6-toothed. Achenes 6-angled; pappus a single row of slender capillary barely roughish bristles. —Erect perennial herbs, often sprinkled with hitter resinous dots, with generally corymbose heads of white, bluish, or purple blossoms, appearing near the close of summer. (Dedicated to Eupator Mithridates, who is said to have used a species of the genus in medicine.)
E. coelestìnum L. (MIST-FLOWER.) Somewhat pubescent, 0.5-1 m. high; leaves opposite, petiolate, triangular-ovate and slightly heart-shaped, coarsely and bluntly toothed; heads many-fiowered, in compact cymes; flowers blue or violet. — Rich soil, N. J. to Mich., Kan., and southw.
This is the most universally beloved of all wild flowers, the focus of countless childhood traditions and the very image of “flower” in the popular imagination. It may be derided as a pernicious weed by agricultural and environmental authorities, but the ordinary citizen will never be persuaded to hate it. The first of the flowers above was blooming in early June at the edge of a gravel lot in Scott Township; the second was blooming in late May on a sunny bank in Mount Lebanon.
Daisies like these were formerly kept in the genus Chrysanthemum, but have been removed by bored botanists to the genus Leucanthemum “because they are not aromatic and their leaves lack grayish-white hairs,” according to the Wikipedia article on the genus. (The genus “Leucanthemum” was apparently named by Lamarck, whose discredited theory of inheritance of acquired characteristics still haunts high-school biology classes.) Because of this new sorting of the genera, we leave Gray and give the description of the genus and species from the Flora of North America at efloras.org:
Perennials, (10–)40–130(–200+) cm (rhizomatous, roots usually red-tipped). Stems usually 1, erect, simple or branched, glabrous or hairy (hairs basifixed). Leaves mostly basal or basal and cauline; petiolate or sessile; blades obovate to lanceolate or linear, often 1[–2+]-pinnately lobed or toothed, ultimate margins dentate or entire, faces glabrous or sparsely hairy. Heads usually radiate, rarely discoid, borne singly or in 2s or 3s. Involucres hemispheric or broader, 12–35+ mm diam. Phyllaries persistent, 35–60+ in 3–4+ series, distinct, ovate or lance-ovate to oblanceolate, unequal, margins and apices (colorless or pale to dark brown) scarious (tips not notably dilated; abaxial faces glabrous or sparsely hairy). Receptacles convex, epaleate. Ray florets usually 13–34+, rarely 0, pistillate, fertile; corollas white (drying pinkish), laminae ovate to linear. Disc florets 120–200+, bisexual, fertile; corollas yellow, tubes ± cylindric (proximally swollen, becoming spongy in fruit), throats campanulate, lobes 5, deltate (without resin sacs). Cypselae ± columnar to obovoid, ribs ± 10, faces glabrous (pericarps with myxogenic cells on ribs and resin sacs between ribs; embryo sac development monosporic); pappi 0 (wall tissue of ray cypselae sometimes produced as coronas or auricles on some cypselae). x = 9.
Species 20–40+ (3 in the flora): introduced; mostly temperate Europe (some widely cultivated and sparingly adventive).
The three leucanthemums recognized here are weakly distinct and are sometimes included (with a dozen or more others) in a single, polymorphic Leucanthemum vulgare.
SELECTED REFERENCE
Vogt, R. 1991. Die Gattung Leucanthemum (Compositae–Anthemideae) auf der Iberischen Halbinsel. Ruizia 10: 1–261.
Chrysanthemum leucanthemum Linnaeus, Sp. Pl. 2: 888. 1753; C. leucanthemum var. pinnatifidum Lecoq & Lamotte
Perennials, 10–30(–100+) cm. Stems simple or distally branched. Basal leaves: petioles 10–30(–120) mm, expanding into obovate to spatulate blades 12–35(–50+) × 8–20(–30) mm, margins usually pinnately lobed (lobes 3–7+) and/or irregularly toothed. Cauline leaves petiolate or sessile; blades oblanceolate or spatulate to lanceolate or linear, 30–80+ × 2–15+ mm, margins of mid-stem leaves usually irregularly toothed proximally and distally.Involucres 12–20+ mm diam. Phyllaries (the larger) 2–3 mm wide. Ray florets usually 13–34+, rarely 0; laminae 12–20(–35+) mm. Ray cypselae 1.5–2.5 mm, apices usually coronate or auriculate. 2n = 18, 36, 54, 72, 90.
Some botanists (e.g., W. J. Cody 1996) have treated Leucanthemum ircutianum de Candolle, with blades of mid and distal cauline leaves oblong to oblong-lanceolate and not ± pinnate at bases, as distinct from L. vulgare.
