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Boston ivy is an exotic introduced from Asia; it is a woody vine up to 50' long (with occasional branches) that grows on or over fences, walls, concrete, masonry, and trees. The lower stems are woody and produce small brown rootlets to adhere to surfaces; upper stems are (also) hairless, green to orange-red in color, with branched tendrils that have adhesive pads at their tips. Leaves are alternate, 6" long and across exclusive of the long, slender petioles, palmately tri-lobed with undulating or crenate margins. Cymes of flowers lacking a distinct central axis arise from the leaf axils; the cymes are 4" in both dimensions. Individual flowers are 1/4" across; they have five yellowish-green petals, five stamens with yellow anthers, and a single style. Fertilized flowers produce berries 3/8" across. When mature the berries are dark blue with a whitish bloom, usually hidden beneath the leaves; the flower stalks are yellow- or brownish-green or a dull orange-red.

Parthenocissus

Parthenocissus tricuspidata

Boston ivy [Blooms: ??]

Woodbine is a woody vine that usually uses trees as a substrate; the vine can be as much as 60' long. The stem is initially green and hairless; as it matures it becomes woody and develops a reddish- or grey-brown color. The leaves are alternate, palmately compound, usually with five (rarely 4 or 7) leaflets that are about 5" long and 2.5" wide with coarse marginal teeth, shiny-green when young but getting duller with age; the compound leaf has a slender 6-8" long petiole. Three- to six-inch-long clusters of 10-75 flowers arise from the main vines opposite the leaves; the clusters have two main branches and multiply-branched flower stalks with no clear central stem. Individual flowers are inconspicuous, 1/4" across with five yellowish green petals with narrow margins perpendicular to the plane of the petal and a pointed, curled tip; the petals are initially spreading but later become reflected backwards. In the center of the flower are five pale red stamens with creamy white or purple anthers, a reddish ovary, and a single white, stubby, conical style. The fruits are round blue-black berries 3/8" across that are reminiscent of grapes in a cluster with red, branched flower stalks; each berry contains four seeds. Woodbine has palmate leaves with five leaflets, very similar to Virginia creeper (Parthenocissus quinquefolia), but lacks the distinctive aerial roots "bearded" with short tendrils that are present in Virginia creeper. Opposite the base of the leaf petiole on the stem, woodbine produces a thin filament that branches 2-3 times, anchoring the vine by twining around objects. In Virginia creeper, the equivalent filaments are stouter, branch up to 10 times, and end in robust, egg-shaped pads that attach to the substrate. The inflorescence of woodbine lacks a central axis; the inflorescence of Virginia has a distinct central axis. Wikipedia (https://en.wikipedia.org/wiki/Parthenocissus_inserta) lists other differences between the two species. Illinois Wildflowers, USDA Plants, and and World Flora Online consider the two species to be one; Minnesota Wildflowers considers them to be separate and distinct. Flora of North America indicates the correct scientific name for woodbine is Parthenocissus vitacea (not P. inserta), as does ITIS and MissouriPlants.com, implying that woodbine and Virginia creeper are distinct species. Both woodbine and Virginia creeper have 40 chromosomes. Lu et al.'s (2012, 2023) molecular and morphological analyses indicate that woodbine and Virginia creeper are very closely related but are distinct species, and I'll consider that to be correct here.

Parthenocissus

Parthenocissus vitacea

woodbine [Blooms: ??]

Wild parsnip is an exotic plant, native to Eurasia, in the carrot family (Apiaceae); it produces flat umbels of flowers (like Queen Anne's lace, except yellow). This is the wild version of the domestic parsnip. The compound umbels are 3-8' across, flat topped, with 15-25 umbellets; each umbellet includes 15-35 1/8" yellow flowers borne on 3/8" long pedicels. Individual flowers have five very short, yellow petals, initially curled inward, but later the petals reverse curvature and curl outwards; there are also five yellow stamens and two styles that arise from an ovary with a swollen, greenish-yellow nectar pad. The fruits are 1/4" long flat, oval, coin-like discs; when mature the disk is brown and the edges of the disk are winged.

Pastinaca

Pastinaca sativa

wild parsnip [Blooms: May-Jun]

Ditch stonecrop is native to North America; its range includes the majority of the states in the U.S. and the provinces in Canada. It is a small (1-2' tall) plant with green or red stems, usually unbranched. Cymes of flowers 1-3" across arise from the upper stems, each cyme with 2-4 spreading flowering stalks; flowers are restricted to only one side of the flower stalks. Individual 1/4" flowers are yellowish-green to white, have five spreading, green sepals, ten stamens with cream-colored or yellow-orange anthers, and five beaked carpels, each with a single style and a green stigma; petals are completely absent. (The carpels look rather like a teapot with no handle and a very wide spout, or like a "duck" wine decanter. Look it up.) The carpels become the seed capsules; they turn bright red when mature. Ditch stonecrop prefers wet habitats (like ditches). It is completely unrelated to biting stonecrop (Sedum acre).

Penthorum

Penthorum sedoides

ditch stonecrop [Blooms: Aug-?]

Waterpepper is a rather spare plant, 1-2' tall which needs close observation to be appreciated. 2-7" long spikes of minute flowers, only a few of which are open at any one time, terminate the upper stems; the flower spikes often nod or droop. Each greenish-white flower is ~1/8" long with five tepals covered with glandular pits (see below), green towards the base, brilliant white at the tips, 4-6 white stamens, and 2-3 white styles. The flowers never open very far. P. hydropiper is distinguished by (usually) reddish stems and the presence of tiny glandular pits (often pale yellow or brown, and only visible with magnification) on the greenish portions of the tepals. Cultivated varieties of waterpepper have been eaten in Japan and Europe, but the wild form produces a variety of oils that can cause skin (including the oral mucosa) irritation and swelling.

Persicaria

Persicaria hydropiper

waterpepper [Blooms: Aug-Sep]

Pale smartweed is a very tall smartweed (2.5-4') characterized by long, dense, drooping, whitish flower clusters and the absence of bristles on the leaf sheaths (ocreae). Stems terminate in drooping flower spikes 2-8" long, densely packed with small (1/8" long) flowers. Individual flowers have 4-5 greenish-white to pinkish tepals, 5-6 stamens with pink anthers and two styles. Because the flowers open only at their tips, the reproductive structures are difficult to observe. After fertilization, a three-angled seed, 2 mm across, develops nestled in the tepals. This is the largest smartweed that occurs in Illinois. Pale smartweed prefers wet soils (e.g., the shores of water bodies). Pale smartweed is similar to Pennsylvania smartweed (Persicaria pennsylvanica) but that plant has erect, cylindrical flower spikes and the flowers are pink or reddish.

Persicaria

Persicaria lapathifolia

pale smartweed [Blooms: Jul-Oct]

Creeping smartweed is another weedy exotic, but its charm increases as you look closer. The flower spikes are 1.5" long and <1/4" wide; they are covered with tiny (~1/8" long) flowers with five pink tepals, only a few of which are open at any one time. (Petals are absent.) There are five stamens with pink or yellow anthers and three styles hidden within the flower; they are visible only with difficulty. At the base of each flower is a small membranous sheath with bristles as long or longer than the flowers (not present on all flowers). After fertilization, a three-angled seed that tapers to a point on each end develops nestled in the tepals. This is an Asian species that was introduced to North America around 1910 near Philadelphia and reached Illinois in the 1940's; it strongly prefers wet soils. Creeping smartweed resembles lady's-thumb (Persicaria maculosa), but creeping smartweed's sprawling habit and the long bristles associated with the flowers are distinctive.

Persicaria

Persicaria longiseta

creeping smartweed [Blooms: May-Oct]

Lady's-thumb is an exotic, native to Europe, but has a long history in North America — it was first reported from the Great Lakes in 1843. Flower spikes (racemes) are 1/2-1.5" long and densely covered with tiny (1/8" long) pinkish-white flowers; flower color is quite variable, even within a single flower spike. The flowers are "shy" and often open only at the tips of the 4 or 5 sepals (there are no petals); both the six stamens and the single style (divided into three towards the distal end) remain hidden. Seeds are black; they develop singly within the persistent sepals and remain largely hidden by the sepals; they can be found on flower heads still blooming. Lady's-thumb prefers wet habitats.

Persicaria

Persicaria maculosa

lady's-thumb [Blooms: Jun-Sep]

Pennsylvania smartweed flower spikes are 3/4-2" long, distinctly cylindrical with a blunt tip, erect, and densely covered with white, pink, or reddish flowers, only a few of which are open at any time. The peduncle of the flower spike is usually covered with short glandular hairs. Individual flowers are ~1/8" long, and have five tepals (white, light pink, or rose pink), 6-8 stamens with yellow, white, or pink anthers and two styles. Pennsylvania smartweed is a particularly variable species and may be difficult to identify unequivocally. If the stems zig-zag between nodes, if the flower stalks' peduncules are covered with glandular hairs, or if the flower spikes are short, cylindrical and erect, the specimen is likely to be Pennsylvania smartweed, but any or all of these features may be missing.

Persicaria

Persicaria pensylvanica

Pennsylvania smartweed [Blooms: Jul-Sep]

Dotted smartweed (Persicaria punctata) is a very common smartweed in Illinois wetlands. The upper stems produce spike-like racemes 2-6" long with white to greenish-white flower buds and flowers sparsely distributed along their length. Individual flowers are about 1/8" long with five white tepals covered with glandular depressions (best viewed with a hand lens). There are 6-8 stamens with red or pink stamens; the single style divides into two or three branches near its base. The flowers only open at their tips. The single seed is three-angled, oblong, and shiny brown to black; it remains tightly enclosed in the tepals as it develops. In Jackson Park, only dotted smartweed and waterpepper (Persicaria hydropiper) have glandular depressions on the surface of the flower tepals.

Persicaria

Persicaria punctata

dotted smartweed [Blooms: Aug-Sep]

Clammy groundcherry flowers arise at the junction of two branches or at a leaf axil on 1/4", arching pedicels that permit the flower to droop. The flowers are up to 3/4" across, consisting of a green calyx half the length of the flower with five triangular teeth, a funnel-shaped, pale-yellow corolla with five shallow lobes, five stamens with large, creamy-yellow anthers, and a single central pistil. In the interior of the corolla surrounding the ovary are five brown smudges, one on each corolla lobe, that merge centrally into a purple-brown ring covering the ovary. Both the pedicel and the calyx are also covered with fine white hairs. After fertilization, the flowers are replaced by green (later brown) hollow husks (a persistant calyx), heart-shaped in longitudinal section, covering a 1/2" diameter spherical, green fruit that becomes yellow when ripe. All parts of clammy ground cherry contain a glycoalkaloid poison called solanine that causes a series of unpleasant and sometimes potentially fatal symptoms; clammy groundcherry is avoided by mammalian herbivores. Only the RIPE fruit is edible.

Physalis

Physalis heterophylla

clammy groundcherry [Blooms: Jul-Aug]

Smooth groundcherry flowers are yellow, bell-shaped, with five purplish-brown patches near the center, five stamens with yellow or purple anthers, and a single pistil; the flowers are suspended from a purplish-green pedicel 3/4-1" long. After fertilization, the flowers are replaced by a tomatillo-like fruit (often with ten purple meridional lines) that is a green (later brown) hollow husk (a persistant calyx) that is heart-shaped in longitudinal section, covering a 1/2" diameter spherical, green miniature tomato that becomes yellow when ripe. All parts of smooth groundcherry contain a glycoalkaloid poison called solanine that causes a series of unpleasant and sometimes potentially fatal symptoms; smooth groundcherry is avoided by mammalian herbivores. Only the RIPE fruit is edible (said to taste like an underripe strawberry).

Physalis

Physalis longifolia

smooth groundcherry [Blooms: Jun-Aug]

Ninebark produces round or domed clusters (racemes) of 30-50 flowers on the tips of young stems. Individual flowers are about 1/2" across; they have a light green calyx with five triangular teeth, five white petals, 30-40 pink-tipped stamens, and 3-5 styles with yellow stigmas. The inside surface of the flower between the styles and the base of the stamens (the hypanthium) is prominently colored tan, orange, or red. After fertilization, each flower produces 2-5 adjacent fruits "follicles"), greenish-red in color, drooping from the long, slender flower pedicels. Single follicles contain a single, hard seed; the follicles are about 8 mm long with a slender, pointed beak protruding from one side. There are two varieties of ninebark characterized by whether the surface of the follicle is hairy; the variety present in Jackson Park (var. intermedius) has a hairy surface.

Physocarpus

Physocarpus opulifolius

ninebark [Blooms: May-Jun]

Pokeweed inflorescences are cylindrical, 3-6" long and 1" in diameter with 1/4" flowers radiating in all directions on short green or white pedicels. Individual flowers have five pink or white sepals and ten white stamens in a circle around fused carpels that form a lobed dome with ten tiny, thread-like styles in the center; petals are absent. The fruit is a 1/4" wide M&M-shaped berry that becomes dark purple and shiny when ripe; the pedicels also turn reddish-purple. Pokeweed is impossible to confuse with any other local plant. Children appear to be especially sensitive and may need hospitalization after eating only a few ripe berries.

Phytolacca

Phytolacca americana

pokeweed [Blooms: Jun-Oct]

The stems and flower stalks of Jacob's ladder are green to reddish-green and hairy; the flowers occur in panicles of floppy flowers on 1" long pedicels. The flowers are bell-shaped and baby-blue in color, 3/8" across with fine longitudinal veins. There are five stamens with white anthers and a long style tipped with a Y-shaped stigma. The stamens do not project beyond the flower margins, but the style does. The fruit is an ovoid, three-celled, seed capsule about 1/4" long held in the remnants of the calyx. Jacob's ladder prefers shady woodlands. This species is similar to Greek valerian (Polemonium vanbruntiae) but the latter species has stamens that extend beyond the flower margins (and does not occur in Illinois).

Polemonium

Polemonium reptans

Jacob's ladder [Blooms: Apr-May]

Prostrate knotweed is a summer-blooming Eurasian exotic that is widespread and ubiquitous across Illinois. One to five 2-3 mm long flowers occur in a cluster at the base of the leaves; the flowers have very short petioles but may appear sessile. Individual flowers have five white or green and white sepals, no petals, five or eight stamens with yellow anthers, and three styles (one for each carpel) fused into a single pistil with a tripartite yellow stigma fringed with short hairs. The fruit develops within the persistant sepals of the flower. Prostrate knotweed is not fussy about its habitat and withstands a fair amount of foot traffic.

Polygonum

Polygonum aviculare

prostrate knotweed [Blooms: Jun-Sep]

Common purslane has no inflorescence per se; flowers occur alone or in small terminal clusters. Individual flowers are 1/8-1/4" across with two or four green sepals, 4-6 yellow petals with notched tips, 6-12 stamens with yellow anthers, and a five-lobed style with 3-6 stigmas. Fertilized flowers are replaced by an oval or urn-shaped capsule about 8 mm long that splits open along a meridional seam to release the tiny, dark brown or black seeds.

Portulaca

Portulaca oleracea

common purslane [Blooms: Jun-Sep]

Rough cinquefoil is considered to be native to both North America and Eurasia. Flowers may develop from the axils of the upper leaves but more usually occur (as a panicle of cymes) in a terminal inflorescence on flower stalks 1-2' tall. The flowers are small (1/3-1/2") and pale yellow; the petals are distinctly heart-shaped with narrow bases and the sepals are triangular and slightly longer than petals. About 15-20 yellow stamens surround a dome-shaped, yellow receptacle covered with styles. Beneath the sepals are five green oval bracts about the same length as the sepals when the flower is in bloom. Fruits develop as dry seeds (achenes) in the persistent flower calyx. Note that rough cinquefoil’s leaves have three leaflets, common cinquefoil's leaves have five, and prairie cinquefoil's leaves have 7-11.

Potentilla

Potentilla norvegica

rough cinquefoil [Blooms: Jun-Sep]