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Sulfur cinquefoil flowers are 3/4" across, pale yellow with a golden center. Beneath the flowers are green bracts about the same length as the sepals but narrower. The sepals are equilateral triangles that are shorter than the petals while the petals are heart-shaped with the narrow point at the base of the petal (where the yellow color is often more intense). There are 25-30 stamens surrounding the central receptacle; the anthers have one or more central dark spots contrasting strongly with the generally yellow anther (but these spots may be difficult to see). Sulfur cinquefoil is similar to prairie cinquefoil, but sulfur cinquefoil's flowers are yellow, not cream colored and its leaves are palmately compound, not pinnate. After fertilization, the sepals close over the ovary forming a capsule around the maturing seeds. The seeds are dry achenes less than 2 mm long with a coarsely wrinkled, brown surface. Sulfur cinquefoil was accidentally introduced to North America from Europe; the first recorded observation was in Montreal in 1852. By 1879, sulfur cinquefoil had become naturalized in New York state; by 1900, it was spreading across New England and the upper midwest. (So sulfur cinquefoil probably wasn't around for the Columbian Exposition in Jackson Park in 1893.) It spreads aggressively in disturbed areas.

Potentilla

Potentilla recta

sulfur cinquefoil [Blooms: May-Jul]

Common cinquefoil is a sprawling plant less than a foot tall that produces numerous prostrate stolons up to 3' long. Both the stems and the stolons are initially green but become more reddish. The leaves are alternate and palmately compound with five leaflets, each with serrated margins; the leaflets are three to four times longer than wide. The sparse flowers develop singly on long pedicels that arise from the axil of some compound leaves. They are bright yellow and 1/2" across with triangular sepals shorter than petals; the petals are narrowest at their base and usually rounded at their distal edge. About 20 stamens with yellow anthers (turning reddish with age) surrounded a central mass of styles. Common cinquefoil has flowers and leaves that are superficially similar to those of mock strawberry (Duchesnea indica). However, the leaves of common cinquefoil have extremely sharp-edged, well-defined teeth on the leaf margins (strongly resembling the edge of a hand saw), not the bluntly-tipped teeth of mock strawberry. The five small bracts (leaves) just below the sepals in mock strawberry, each with three pointed lobes at its tip, are present in both the flowers and berries are diagnostic of mock strawberry; they are absent in common cinquefoil. Note that rough cinquefoil’s leaves have three leaflets, common cinquefoil's leaves have five, and prairie cinquefoil's leaves have 7-11 leaflets.

Potentilla

Potentilla simplex

common cinquefoil [Blooms: May-Jul]

Shooting star's smooth, leafless flower stalk is reddish-green, bearing 6-20 (sometimes up to 40) nodding flowers at its apex that are suspended from delicate pedicels. Each flower has a green calyx with five short, triangular green lobes, five white or pale lavender petals reflexed backwards (upwards) and often twisted along their lengths. A "reproductive cone" (five yellow to purple stamens tightly appressed around a single, purplish-green central style) extends down from the yellow petal bases. The fruit is a short, ovoid seed pod, initially green, turning reddish-brown with maturity, 1/4-3/4" long with a pointed tip that is oriented vertically (the curvature of the pedicel reverses after fertilization); it is filled with small, dark seeds. The flowers of shooting star are superficially similar to those of horse nettle (Solanum carolinense) but the latter do not hang from a long stalk like shooting star (and have lots of prickles and spines that shooting star lacks). The convergent evolution of "reproductive cones" in both shooting star and horse nettle is an adaption to increase the efficiency of buzz pollination by large bees, especially bumblebees. The older name for this species ("Dodecatheon meadia") is no longer considered valid.

Primula

Primula meadia

shooting star [Blooms: Apr-May]

Heal-all (a.k.a., self-heal) is a native species superficially similar to ground ivy (Glechoma hederacea) or early-season henbit (Lamium amplexicaule). Heal-all has the characteristics of other low-growing plants in the mint family — an upright, four-angled stem, with lines of hairs along the ridges, 1' tall or less, with a short (1-2") spike of flowers at the apex — and is thus easy to overlook. But the tiny (1/2" long), tubular, two lipped flowers are distinctive (and charming). The light purple or blue upper lip is bent at right angles to form a hood over the aperture with the four stamens and single style with a bifurcated stigma at its tip curving along inside of the hood. The lower lip is divided into three lobes, the middle one white and fringed; the two smaller lateral lobes are the same color as the hood. The hood of the upper lip also sports a "mohawk" haircut of relatively long hairs along the crest of the hood. The flower calyx is light green or reddish, hairy along the edges. After fertilization, four tiny, brown, finely-ridged nutlets develop within the persistant calyx; the seeds are reported to be dispersed by a mechanism that uses the energy in raindrops impacting the calyx to fling the seeds away from the mother plant. The leaves are opposite, up to 2" long and half as wide with a short petiole; they are egg- or lance-shaped with a central vein that is hairy on the underside. Heal-all prefers moist habitats with a history of disturbance.

Prunella

Prunella vulgaris

heal-all [Blooms: Jun-Aug]

American plum flowers first appear before or at leaf emergence; they occur in roughly spherical clusters (umbels) of two to five flowers, arising from leaf axils. Each flower is ~1" across, held away from the twig at the base of the umbel on 1/2-1" petioles; there are five egg-shaped petals with narrow bases, white with a touch of pink, five narrow, somewhat fleshy, green sepals much shorter than the petals, a single style, and numerous (10-30) stamens with tan anthers. The fruits are about 1" across, initially green but turning reddish-purple with the waxy bloom typical of plums when ripe; inside is a single seed (a "stone," like a peach). Because this tree usually flowers when the leaves are only beginning to open, it produces an especially showy display. It is widespread across Jackson Park.

Prunus

Prunus americana

American plum [Blooms: Apr-May]

The floral inflorescence in sweet cherry is a flat-topped corymb of two to six cup-shaped flowers that appears in early spring as the new leaves unfold. Each flower is 1-1.5" in diameter with five green sepals reflexed back along the petiole; five pure white petals; a ring of 20-30 stamens each with a white filament tipped with a yellow, ball-like stamen; and a single pistil with a terminal knob-like, greenish stigma. The fruit is a red to dark purple drupe (stone fruit) 1/2-1" in diameter (a typical cherry).

Prunus

Prunus avium

sweet cherry [Blooms: Apr]

European bird cherry It has showy white flowers (so is widely planted as an ornamental) and reaches heights of 30-40'. Blooms are produced in elongate, cylindrical racemes of 15-50 flowers at the tips of twigs, similar to but shorter than those of chokecherry (Prunus virginia). Individual flowers consist of five green, broadly-spreading or reflexed sepals (longer than wide); five white or cream colored petals that are 1/4-3/8" long, oval but widest in the center; 10-30 stamens half the length of the petals around a cup-shaped, often green hypanthium (hairless externally); and a single central pistil. The fruit is a small, black drupe (cherry) with an extremely bitter taste to mammals, but it is much loved by birds, who disperse the pits. European bird cherry is very similar to another species present in Jackson Park, chokecherry. European bird cherry tends to be more tree-like in habit than chokecherry and tends to have shorter stamens (half the length of the petals) than chokecherry (as long as the petals). It's not clear how much of this expansion is due to Park District policy and how much is due to natural seed dispersal.

Prunus

Prunus padus

European bird cherry [Blooms: Apr-May]

Peach flowers arise along young branches, blooming beginning before the leaves have opened in the spring; the flowers are usually solitary but occasionally occur in pairs. Individual flowers are 1-1.5" long consisting of a burgundy-colored calyx with five rounded apical lobes (sepals); five spreading pink (rarely, white) petals, oval with abruptly narrowed bases ("clawed"); 15-30 stamens with pink filaments and yellow to orange anthers; and a pistil with a single light green style nearly as long as the stamens. Fertilized flowers are replaced by green, fuzzy ovoids, eventually up to 3" long and across and containing a single seed; peach-colored when mature.

Prunus

Prunus persica

peach [Blooms: Apr-May]

Sand cherry is a 4-8' tall shrub; the Great Lakes variant of this species (Prunus pumila spp. pumila) is restricted to the states (and the Canadian province) that touch on the Great Lakes. Blooms occur in umbels of 1-3 flowers; flowers open before the leaves but may persist after some leaves have emerged. Individual flowers are about 1/2" across, consisting of five sepals with rounded tips that are about a third the length of the petals; five white, round- or egg-shaped petals; 10-30 white stamens with yellow anthers emerging from a reddish, cup-shaped hypanthium; and a single, central style. The fruit is a reddish-purple to black, shiny cherry (drupe) about 1/2" in diameter. Sand cherry is found along the shores of the Great Lakes on beaches (sandy, gravelly, or rocky), dunes, and the swales between dunes.

Prunus

Prunus pumila

sand cherry [Blooms: Apr-May]

Black cherry (Prunus serotina) is a is a deciduous tree that can grow up to 80' tall. It typically has a single central trunk below and leafy crown that is taller than wide. Flowers occur in racemes 4-6" long with 20-60 1/2" wide flowers packed around the elongated inflorescence. Individual flowers consist of five green, triangular sepals, five white petals broader at their distal tips and at least three times longer than the sepals, 10-30 stamens with yellow anthers around a reddish-orange hypanthium, and a single, central pistil with a flattened stigma. After fertilization, each flower produces a globoid, fleshy drupe about 1/4" across. The immature cherries are green; as they mature the fruit turns first dark red, they purple-black at maturity. These fruits are sweet but slightly bitter; the black cherry you buy in the grocery store is larger (at least 1/2" across), sweeter, and a species native to Eurasia (Prunus avium).

Prunus

Prunus serotina

black cherry [Blooms: May-June]

Japanese flowering cherry is an exotic from East Asia widely grown in North America as an ornamental (for its showy spring flowers). The flowers occur is small clusters of 2-5 white, pale pink, or deeper pink flowers that (unlike most cherries) dangle face-down beneath the stems from short spurs. The fruit consists of small, round drupes that turn black when mature. Leaves, stems, and fruit, and seeds are toxic to mammals. Many of the cultivars of Japanese flowering cherry are highly hybridized and nearly unrecognizable as being derived from Prunus serrulata.

Prunus

Prunus serrulata

Japanese cherry [Blooms: Apr-May]

Chokecherry is a shrub or small tree 8-25' tall. Flowers occur in spectacular racemes ~6" long with 15-20 white, 1/2" wide, bowl-shaped flowers with an orange-yellow center (hypanthium); the flowers are attached to a central, greenish-yellow stalk. Individual flowers consist of five sepals (initially green, later turning yellow) shorter than the petals, five white petals that narrow sharply near their bases, 15-20 stamens about as long as the petals, and a pistil with a single style. Crushed leaves smell strongly of bitter almonds. Fruit is a red to black globular drupe <1/2" wide that contains a single hard-coated seed (stone) and has a VERY bitter taste; the seed contains high levels of hydrogen cyanide. The fruit is eaten by a wide variety of mammals and birds; the flesh of the fruit traditionally was one of the components of pemmican in indigenous cultures. (The hydrogen cyanide is not a danger unless the hard shell of the seed is broken open.) Chokecherry is similar to wild black cherry (Prunus serotina), but P. serotina has incurved teeth on its leaf margins. Chokecherry is very similar to an exotic also present in Jackson Park, European bird cherry (Prunus padus). European bird cherry tends to be more tree-like in habit than chokecherry and tends to have shorter stamens (half the length of the petals) than chokecherry (as long as the petals). Chokecherry in Jackson Park is often infested with black knot fungus (Dibotryon morbosum).

Prunus

Prunus virginiana

chokecherry [Blooms: Apr-May]

Hoptree (a.k.a., wafer ash) is a large shrub with a rounded, irregular crown and (usually) a robust central trunk up to 6" across. Hoptree may produce single-sex (male or female) or bisexual (male and female organs both present) flowers on the same tree. Individual flowers are about 1/4" across, regardless of gender. Perfect (bisexual) flowers have 4-5 greenish sepals, 4-5 narrow, creamy white petals, 4-5 stamens with hairy white bases and yellow anthers, and a single, flattened green pistil. Male flowers are more or less identical but lack the pistil; female flowers are more or less identical but lack the stamens. The fruits are single seeds 1-1.5" long with a broad, flattened, papery wing extending almost all the way around the seed.

Ptelea

Ptelea trifoliata

hoptree [Blooms: May-Jun]

triped squill is another early spring wildflower native to western Asia and the Caucasus; it tends to grow in clumps of plants 4-6" across. There are (only) two dark green, basal, hairless leaves up to 6" long and ~1/2" wide that widen towards their tips; the margins are smooth. A cluster (raceme) of 3-6 flowers are present on a stalk ("scape") 4-8" tall; overall, the cluster and scape resemble the related wild hyacinths. Each flower has six white tepals with a medial blue stripe. The filaments of the six stamens are flattened and fused together to form a white central, lobed, hollow cone that surrounds the style; the anthers are yellow and lie just inside the tip of the cone. This plant is one of the earliest to bloom in the spring in Jackson Park, but goes dormant in the late spring, basically biding its time until the next year. It prefers moist, well-drained soils.

Puschkinia

Puschkinia scilloides

striped squill [Blooms: Mar-Apr]

Slender mountain-mint flowers occur in small terminal clusters at the tips of the upper stems with distinctive very long, narrow bracts with spine-like tips just beneath the clusters; the bracts are densely covered with short, curled hairs on the blade and longer, bristly hairs along the margins. Individual flowers are tubular, white with scattered purple dots, and about 1/4" long; there is a calyx that is divided several slender green lobes. The corolla is divided into two parts, an upper lip and a lower lip that is divided into three lobes. The four stamens and two styles are also white, but the anthers are purple. The styles have a bifurcated stigma. Slender mountain mint is very similar to Virginia mountain mint (Pycnanthemum virginianum), but several characters make it straightforward to distinguish them. Leaves on slender mountain mints are always less than 1/4" wide and the stems are hairless; Virginia mountain mint will have the larger leaves more than 1/4" wide and has lines of white hairs on the stems. Slender mountain blooms earlier than Virginian mountain mint, but the blooming period of the two species overlaps. All parts of slender mountain mint give off a strong mint-like odor when crushed, but please restrain yourself from excessive foliage-crushing — it's not polite.

Pycnanthemum

Pycnanthemum tenuifolium

slender mountain-mint [Blooms: Jun-Aug]

Virginia mountain-mint flower heads are 3/4-1" across with up to 50 flowers; only a few flowers open at any one time. The flowers are hairy on the outer surfaces, white to light purple in color. Individual flowers are 1/4" across, tubular, and two-lipped; the lower lip is three-lobed with purple spots; four stamens with purple anthers emerge from the lower tube. There are two styles with deeply-notched tips that extend well beyond the edges of the lips of the corolla. The calyx that cups the flower is hairy, light green and has five triangular teeth.

Pycnanthemum

Pycnanthemum virginianum

Virginia mountain-mint [Blooms: Jul-Aug]

Male and female flowers of pin oakare spatially separated but often occur on the same branch. Female flowers have been reduced to only a short, green spike bearing three bright red styles; the female flowers emerge from leaf axils and may occur in clusters of up to three. The male flowers are borne on 1.5-4" long green catkins that dangle from bud clusters at the tip of the previous year's growth. The fruits are egg-shaped or elliptical (hence the species name) acorns 1/2-2/3" long with a deep reddish cap that covers about half the acorn.

Quercus

Quercus ellipsoidalis

Northern pin oak [Blooms: Apr–May]

In bur oaks, both male and female flowers are produced on the same tree, but they are widely separated; the flowers are wind pollinated. Male flowers are borne on drooping, yellowish-green catkins 2-5" long that hang from the tips of the previous year's twigs; individual male flowers consist of 5-20 stamens surrounded by a lobed calyx. Some sources (e.g., http://www.missouribotanicalgarden.org/plantfinder/PlantFinderDetails.aspx?taxonid=280704) assert that the female flowers of bur oak also occur on catkins, but this is incorrect. Instead, the female flowers occur alone or in groups of 2-3 that arise in the leaf axils of new leaves. Individual female flowers are about 3 mm (1/8") long; a short, reddish green stalk (a pistil) covered with appressed scales bears naked reddish-green or light green styles on its tip. The female flowers are wind pollinated. Both male and female flowers form after the leaves begin to unfurl; the male catkins precede the female flowers by one to several weeks. Fertilized female flowers produce one or two acorns; the acorns may be nearly sessile or hang from short (<1") stalks. Mature bur oak acorns are 1.5-2.5" long and the same across (including the caps) — they are the largest acorn of any oak. The caps (= cupules) cover at least half of the length of bur oak acorns, often so much that only a nubbin of the acorn is visible. The caps are covered with coarse scales that have an obvious keel and appear knobby; the marginal scales on the caps bear soft awns up to 8 mm (1/3") long that form a conspicuous fringe above the acorn — this is the "bur" that is referred to in the common name in analogy to the machine tool used for grinding. The acorns mature and germinate over a single summer; they do not need to be exposed to cold to germinate.

Quercus

Quercus macrocarpa

bur oak [Blooms: Apr–May]