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Woodland sunflower flower stalks tend to be hairier than the stem. The flowerheads are 1.5-3" across with 8-15 ray florets with yellow petals (with a tiny notch at the tip) and over 40 yellow, tubular disc florets with five spreading apical lobes. Flower bracts cup the back of the flowerhead in four series, light green, pointed, hairy along their margins, and typically recurved. Only the disc florets are fertile; the ray florets are sterile. Woodland sunflowers can be recognized by their nearly-sessile or sessile, opposite, leaves and broad leaf bases.

Helianthus

Helianthus divaricatus

woodland sunflower [Blooms: Jul-Oct]

Sawtooth sunflower flowerheads are 2.5-4" across with 10-20 bright yellow ray florets and over 100 tubular golden-yellow disc florets with five protruding brown anthers fused around a yellow style with a bifurcated stigma. Behind the flowers are multiple layers of spreading bracts that are pointed with hairy margins, especially near their base. Only the disc florets are fertile; the ray florets are sterile. (This is true throughout the genus Helianthus, although this situation seems more understandable (to me) than the the situation in the genus Silphium, where the opposite is true.) Sawtooth sunflowers can be distinguished from other Helianthus spp. by their hairless, reddish-purple stems; the arching leaves with a longitudinal fold are also characteristic but not definitive.

Helianthus

Helianthus grosseserratus

sawtooth sunflower [Blooms: Jul-Sep]

Downy sunflower is a very attractive sunflower which blooms in late summer. The composite flowers arise directly from the main stem. Each flowerhead is 2-4" across with 15-30 yellow ray florets and over 75 yellow disc florets in a 1" diameter central disk. Individual ray florets are sterile, the "petal" is about 1-1.5" long. Disc florets are about 1/4" long with five triangular lobes at the end of a tubular corolla; five stamens with white filaments (fused around the base of the style) and purple-brown anthers; and a single style, bifurcated at its tip, which protrudes above the stamens.

Helianthus

Helianthus mollis

downy sunflower [Blooms: Aug-Sep]

Western sunflower is a spindly plant that leads a double life. It is a perennial that first produces a very large (1.5' across) basal rosette of leaves; that basal rosette in turn produces a 2-4' tall, nearly leafless, stem. Clusters (a panicle) of 1-4+ flowerheads are present on pedicels less than 6" long emerging from the stem or upper leaf axils. The flowerheads are 1.5-2.5" across, with 8-20 ray florets, each bearing oblong yellow petals, and over 50 tubular, yellow disc florets with five lobes on their tips and five protruding brown anthers fused around a yellow style with a bifurcated stigma. Only the disc florets are fertile; the ray florets are sterile. (True throughout the genus Helianthus, although that seems more understandable (to me) than the situation in the genus Silphium, where the opposite is true.) Behind the flowerhead are 20-25 lance-shaped bracts (phyllaries) 5-7 mm long with pointed, green or straw-colored tips; there are often hairs round the margins of the phyllaries. The long, sparsely-leaved stem is diagnostic.

Helianthus

Helianthus occidentalis

western sunflower [Blooms: Aug-Sep]

Jerusalem artichoke should rightly be called a "sunflower" like the other four members of the genus Helianthus present in Jackson Park. Five to fifteen flowerheads ride on hairy peduncles up to 8" long and are 2.5-3.5" across; each is cupped by 2-3 overlapping series of phyllaries (bracts) that are more triangular than lance-shaped, hairy, and sharply pointed. The flowerheads consist of 10-20 sterile, yellow ray florets; the 60+ fertile disc florets consist of tubular yellow corollas about 1/4" long with five lobes at their apex and five protruding brown or black anthers fused around a yellow style with a bifurcated stigma. Jerusalem artichoke was cultivated by the indigenous peoples of the midwest for its tasty and carbohydrate-rich tubers.

Helianthus

Helianthus tuberosus

Jerusalem artichoke [Blooms: Aug – Oct]

Ox-eye sunflower (aka, false sunflower) flowerheads are 1.5-3.5" across with a prominant, gumdrop-shaped central disk; the plane of the flowerhead is horizontal, not vertical like most other (true) sunflowers. The 1.5-3" wide flowerheads consist of 10-18 yellow, tubular ray florets with yellow to golden-yellow, elongate-oval petals with notched tips and with two longitudinal folds in each petal; the numerous (10 to over 75) disc florets are yellow, tubular with five (brighter) yellow spreading apical lobes on the tubular corolla. Both disk florets and ray florets have a protruding, bifurcated style; the disc florets also have five stamens with brownish anthers which encircle the style below the paired stigmas. Behind the flower are two series of hairy bracts, the outer layer longer than the inner (a diagnostic character) and a velvety pedicel 1-8" long. Ox-eye sunflower is a "false sunflower" because both the ray and disc florets are fertile and can produce seeds; in true sunflowers, only the disc florets produce seed. The posture of the flower (horizontal rather than nodding towards the vertical) is also distinctive.

Heliopsis

Heliopsis helianthoides

ox-eye sunflower [Blooms: May-Jul]

Day lily stems/flower stalks are 3-6' tall and hairless; 5-9 flowers arise on a small panicle. The flowers are erect, orange with a yellowish center but without spots, large (3-4" wide), with six tepals (petals and similar sepals) with a white medial line and tips that curl backwards. The margins of the tepals are rolled inwards. The flowers have a single straight style and six stamens that curve markedly upwards. The flowers last only a single day. (Thus, the common name.) The seedpods are six-lobed, egg-shaped, and internally divided into three compartments, but the black seeds are inviable; day lilies are a sterile triploid hybrid that has escaped cultivation and reproduces only vegetatively. Day lily is considered invasive and spreads easily. The flowers can be cooked and eaten like squash blossoms and the leaves and tubers are edible when young, but day lilies are extremely toxic to cats and, to a lesser degree, dogs. Day lily is easily distinguished from the other common lily in Jackson Park, Michigan lilies, by the lack of spots on flowers and leaves that are basal and sword-like rather than in whorls around the stem and a horizontal orientation rather than pointing down. According to Flora of North America, day lilies were imported from Asia to Europe in the seventeenth century and to North America in the nineteenth century.

Hemerocallis

Hemerocallis fulva

day lily [Blooms: Jun-Jul]

Cow parsnip flowers are present in 6-8" wide, flat umbels (like Queen Anne's lace) that arise from the central stem or from leaf axils. Beneath each flower cluster are four or more needle-like, fuzzy green bracts; the bracts fall off after the fruit begins to form. Individual flowers are 1/4" across with five white petals that are notched at their tips; in flowers on the edge of an umbel, one petal is visibly larger than the other four. A somewhat lumpy, cream-colored, hairy ovary occupies the center of the flower from which arise two short styles; five stamens with pale yellow anthers arc laterally from under the ovary. Each fruit is heart-shaped, flattened, and contains two seeds.

Heracleum

Heracleum sphondylium

cow parsnip [Blooms: May/Jun-?]

Dame's rocket flowers occur in clusters (racemes) of up to 30. Each flower is 3/4-1" across and long, with a long, narrow, tubular, pinkish-green calyx composed of four long narrow sepals. The calyx opens through a narrow throat into four rounded, pinkish-purple (sometimes white) petals; the six pale yellow stamens and the multiple styles poke to various degrees out of the throat. Stems, leaves, pedicles, and the flower calyxes are all downy or hairy. The fruits are long (up to 4"), narrow, ascending, downy cylinders (siliques, typical of mustards) filled with flattened, oblong seeds. The flowers are very phlox-like, but phlox flowers have five petals, and dame's rocket only has four; phlox leaves are opposite on the stem (not alternate) and are narrower.

Hesperis

Hesperis matronalis

dame's rocket [Blooms: Apr-May]

Flower-of-an-hour flowers are borne singly on hairy flower stalks that arise from the leaf axils; the flowers are 2" across, with five partially-overlapping petals that are white or pale yellow with deep purple bases. Sepals are pale green, translucent, and membranous with deep purple, hairy veins. The numerous stamens are borne on a "staminal column" that surrounds the base of the style; the filaments are maroon and the anthers are golden yellow. The single style is white where it rises above the staminal column and is divided at the tip into five knobby stigmas.

Hibiscus

Hibiscus trionum

flower-of-an-hour [Blooms: Jul-Sep]

American hops male and female flowers occur on separate plants. Actual female (pistillate) flowers occur in tight clusters ("aments") 3/4" long of 10-50 flower pairs on a stalk that arises from a leaf axil, each pair subtended by a bract; each flower has two long, thin styles. Male flowers have five pale green spreading sepals and five short, banana-shaped stamens. The fruit is a cone-like structure of overlapping bracts (originally present at the base of the female flowers) that surround the seeds; it is (obviously) found only on the female plants.

Humulus

Humulus lupulus

American hops [Blooms: Jul-Sep]

Wild hydrangea canes produce a flat terminal panicle 3-6" across with 100-500 flowers of two kinds — small, fertile flowers filling most of the area and a few, sterile pseudo-flowers around the margin that are 3-4 times larger than the flowers in the center and seem to function only as an advertisement for pollinators. The central, fertile flowers are about 1/4" across with a green calyx made of five separate sepals; five greenish-white or cream petals about 1/8" long; 8-10 stamens with long filaments and oblong, white anthers; and a pistil bearing two styles with knob- or club-like stigmas. The sterile, outer pseudo-flowers have 3-4 fused petal-like, white bracts (or sepals; sources differ) with a central structures that visually is reminiscent of stamens or styles; the pseudo-flowers persist long after the inner flowers have been fertilized and have produced a two compartment seed pod that is ribbed and bears a pair of tiny horns (the styles) on its upper end. Wild hydrangea is relatively rare in northern Illinois; in Jackson Park it prefers wooded area by walking paths.

Hydrangea

Hydrangea arborescens

wild hydrangea [Blooms: Jun-Aug]

Virginia waterleaf stems are variable in color (green, reddish-green, or reddish-brown) and up to 2' tall. Each upper stem has at their tips one or two clusters (cymes) of 8-20 flowers that is 1-2" in diameter on a 4" stalk (peduncle); the central flower opens first. Individual flowers are 1/4-1/2" long, roughly bell-shaped, white, pink, or light violet in color. Flowers have a green, hairy calyx with five long, narrow teeth fringed with widely-spaced, stout hairs; a tubular corolla with five equal lobes at the open end; five stamens covered with long hairs along their lower half, with anthers initially yellow that later turn dark brown; and a single lavender style with a white, bifurcated tip. Both the stamens and the style are 30-50% longer than the corolla lobes and extend well beyond their edges.

Hydrophyllum

Hydrophyllum virginianum

Virginia waterleaf [Blooms: May]

Giant St. John's wort stems and branches terminate in clusters (cymes) of 1-5 flowers 2-2.5" across; the central bud opens first. Giant St. John's wort has the largest flower of all the St. John's worts found in Illinois. Each flower has five green sepals 1/3 the length of the petals; five bright yellow, often twisted, petals; more than 100 yellow stamens with yellow anthers; and a yellow-green pistil with five distinct styles fused at their bases, each with red stigmas at their tip. Five carpels are present in the flask-shaped ovary. The fruit is a five-chambered, bullet-shaped structure up to 1.25" long and 1/2" wide, initially green, turning brownish-black with maturity; the capsule is topped with the remnants of the (five) styles and contains numerous lozenge-shaped, 1 mm long, black seeds. (When fully mature and with appropriate magnification, the seeds look like ears of corn.) Note in particular the very large (2") flowers and the five styles on the pistil of giant St. John's wort — most other Hypericum spp. have either one or three styles. Kalm's St. John's wort also has five styles, but that is a much smaller and woody plant with narrower leaves and much smaller flowers.

Hypericum

Hypericum ascyron

giant St. John's wort [Blooms: Jun-Aug]

Kalm's St. John's wort is a 1-3 ' tall shrub, largely restricted to the Great Lakes basin of the U.S. and Canada; it is formally listed as "critically endangered" in Illinois (but is quite common in Jackson Park). The flowers occur in clusters (corymbs) of 3-7. Individual flowers are 1-1.25" across; they have five light green, lance-shaped sepals half the length of the petals, five spreading golden-yellow petals, 150-200 stamens with yellow anthers, and a five-lobed yellow ovary with five (partially or completely fused) styles. The ovary often is markedly five-lobed. The fruit is a teardrop-shaped capsule resting on the five widely-spread sepals containing five (occasionally four) carpels; the capsules are initially green, then turn bright red, then finally brown as the numerous black, oblong seeds mature. Woody lower branches and the strongly five-lobed pistil and fruit are distinguishing characters that separate this species from other Jackson Park St. John's worts.

Hypericum

Hypericum kalmianum

Kalm's St. John's wort [Blooms: Jun-Aug]

Common St. John's wort flowers are ~3/4" across, with five green sepals, five oblong yellow petals, three widely-spreading styles (and three carpels) with scarlet stigmas on top of a globular yellow ovary, and numerous (45-85) stamens with yellow anthers. The filaments of the stamens fuse into three groups near their bases. Unique among the St. John's worts in Illinois, common St. John's wort has petals with tiny black dots (glands full of essential oils) that are restricted to the petal margins. (Hypericum punctatum, spotted St. John's Wort, also has black dots on the petals but, in that species, they extend to the interior of the petals.) These black glands may also occur sparsely on the anthers. The fruit is a three-chambered, bullet-shaped structure 1/4" long, initially green, turning reddish-brown with maturity; the capsule is topped with the remnants of the (3) styles and contains numerous seeds. Common St. John's wort contains chemicals that may interact adversely with a number of common pharmaceuticals despite its widespread use in traditional medicine and may be toxic to livestock in large doses.

Hypericum

Hypericum perforatum

common St. John's wort [Blooms: Jun-Aug]

Shrubby St. John's wort is, as the name says, "shrubby;" the "prolificum" part refers to the exceptionally numerous stamens. The upper stems and axils of the two upper pairs of leaves produce clusters of 3-7 flowers. Flowers are ~1" across, with five green sepals much shorter than the petals, five yellow petals, 150-500 stamens, and a pistil with three styles united at the base and appressed along their lengths. The fruit is a capsule <1/2" long, cone shaped and tapering to the tip, with the tips of the three styles persistant, not lobed but bluntly triangular with three compartments internally (corresponding to the three carpels of the ovary). Hypericum prolificum and Hypericum kalmianum both have woody lower branches (the only Hypericum sp. that do) and are very similar vegetatively, but H. kalmianum produces a seed capsule with the remnants of five styles and has five internal compartments while H. prolificum produces seed capsules bearing the remnants of three styles and has three internal compartments.

Hypericum

Hypericum prolificum

shrubby St. John's wort [Blooms: Jun-Aug]

Round-fruited St. John's wort flowers are 1/2-3/4" across, with five (sometimes four) green sepals shorter than the petals, five rounded, bright-yellow petals with curled margins and tips, 45-85 yellow stamens with orange anthers, and a slender, flask-shaped pistil with three styles fused at their bases bearing tiny stigmas. The fruit is globular with a long, tapering neck, not a lobed bullet-shape as in other Hypericum. Descriptions of this species say it has three styles, but the populations in Jackson Park typically have flowers with what is apparently single style but close inspection (especially of older flowers) show actually has three styles, closely appressed. The styles separate at their tips late in blooming or early in the development of most fruits.

Hypericum

Hypericum sphaerocarpum

round-fruited St. John's wort [Blooms: Jun-Jul]