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Tall ironweed's inflorescence is a flat-topped panicle arising from the tip of the central stem; it is 6-16" across, open and spreading. There are 10-30 disk florets in a tall ironweed flowerhead. The base of the flowerhead is covered by several series of dark colored, broadly oval appressed bracts (phyllaries), often with fine hairs around their edges. The disk florets have tubular, trumpet-like corollas with five recurved lobes; ray florets are absent. Tall ironweed has a much more "open" composite flowerhead than the other ironweeds in Jackson Park, with the trumpet bases of the disk florets easily visible. The fruits are naked, gray or brown, bullet-shaped seeds with a tuft of both short and long tawny or pale purple hairs. To sort out the Jackson Park ironweeds: (1) if both leaves and stem are densely covered with fine white hairs, the leaves are about 3-4 times longer than wide, and each flowerhead has more than 30 disk florets, it's Missouri ironweed (V. missurica). (2) If both leaves and stems are hairless, there are less than 30 disk florets, and the leaves are narrow (typically a half inch or less; about 6-10+ times longer than wide), it's smooth ironweed (V. fasiculata). (3) If the stems and leaves have only short hairs, there are less than 30 disk florets, and the leaves are about 2" wide and 4-6 times longer than wide, it's tall ironweed (V. gigantea).

Vernonia

Vernonia gigantea

tall ironweed [Blooms: Jul-?]

At the tip of a Missouri ironweed stem, a corymb of composite flowerheads (the inflorescence) is produced. The stems of the inflorescence are also covered in fine white hairs and usually reddish brown in color. Individual flowerheads are magenta and rayless; ray florets are completely absent. Flowerheads contain 32-60 disk florets, each 1/2-3/4" across, which have rounded or broadly angled bracts (phyllaries) with sharp tips, dull green or reddish brown in color, that are layered like fish scales around the base. To sort out the Jackson Park ironweeds: (1) if both leaves and stem are densely covered with fine white hairs, the leaves are about 3-4 times longer than wide, and each flowerhead has more than 30 disk florets, it's Missouri ironweed (V. missurica). (2) If both leaves and stems are hairless, there are less than 30 disk florets, and the leaves are narrow (typically a half inch or less; about 6-10+ times longer than wide), it's smooth ironweed (V. fasiculata). (3) If the stems and leaves have only short hairs, there are less than 30 disk florets, and the leaves are about 2" wide and 4-6 times longer than wide, it's tall ironweed (V. gigantea).

Vernonia

Vernonia missurica

Missouri ironweed [Blooms: Jul-Oct]

In corn speedwell, single flowers 1/8" wide develop at the tips of inflorescences that arise from the axils of the middle and upper leaves; the flowers are nearly sessile. The inflorescence continually elongates, producing new flowers and a series of bracts along its length. The most basal bracts resemble the stem leaf whose axil hosts the inflorescence; the upper bracts are alternate, 3-10 mm long, and narrowly lance-shaped with long hairs fringing the bract margins. Each flower consists of four hairy, green, lance-like sepals/bracts longer than the corolla lobes; a blue to blue-violet corolla with four petal-like lobes, the upper three lobes slightly larger than the lower forth lobe; two stamens with white anthers; and a pistil with a single style. Dark lines (nectar guides) radiate from the throat of the corolla. Each flower only lasts a single day. The fruit is a 1/8" long and wide, tan, heart-shaped seed capsule, somewhat flattened, with two compartments containing 10-30 yellowish, ovoid seeds. There are 16 species of the genus Veronica reported from Illinois. I have only seen three (Veronica arvensis, Veronica polita, and Veronica serpyllifolia) in Jackson Park but, given their minute size and inconspicuousness, it seems likely that more remain to be found.

Veronica

Veronica arvensis

corn speedwell [Blooms: Apr-Jun]

ird's-eye speedwell (Veronica persica) flowers are solitary, arising from the axils of upper leaves on 1/2-3/4" long, hairy pedicels with a leaf-like bract at their bases. Individual flowers are about 8 mm across, consisting of a calyx with four lance-shaped sepals that are fused at their bases and are shorter than the corolla lobes, and a tubular corolla with four lobes ("petals") that are round to oval. The corolla is bluish toward the edges and whitish centrally, with dark blue lines radiating from the center. One of the four lobes is slightly smaller (and whiter) than the other three, so the flower is bilaterally symmetrical. A pistil with a single 2-3 mm long style arises from the center of the flower; two white stamens with dark blue anthers flank the pistil. Fertilized flowers produce a two-lobed fruit nestled in the remnants of the calyx, each lobe containing 5-11 small seeds; the fruit is a laterally compressed heart shaped capsule that is longer than tall with a distinct shallow V-shaped groove where the remnants of the style can be seen.

Veronica

Veronica persica

bird's-eye speedwell [Blooms: May]

Wayside speedwell's flowers are 1/4" across with a green, hairy calyx with four triangular lobes as long as the petals, projecting between them in the spaces between petals; a short corolla with four spreading lobes, three the same size (one on either side, blue to bluish-white with dark blue lines, and the third dark blue with blue-violet lines) and one about half as wide, pale blue or white with light blue lines. The blue lines function as nectar guides. The base of all four lobes is bright white, but the center of the flower is greenish. There are two white stamens with white anthers (backed by a dark blue "U" shape) and a single white pistil emerging from the throat of the corolla. The fruits are heart-shaped capsules with two chambers covered with glandular hairs, each containing 8-12 seeds. The flowers and leaves of wayside speedwell are similar to those of bird's-eye speedwell (Veronica persica), but the calyx lobes of bird's-eye speedwell do not project beyond the petals. There are 16 species of the genus Veronica reported from Illinois. I have only seen three (Veronica arvensis, Veronica polita, and Veronica serpyllifolia) in Jackson Park but, given their minute size and inconspicuousness, it seems likely that more remain to be found.

Veronica

Veronica polita

wayside speedwell [Blooms: Apr-Jun]

Wild pansy's flower stalks are long, hairless, and bend like a shepherd's crook just below the base of the flower so the flower axis is approximately horizontal. Individual flowers have five 7-15 mm long, lance-shaped sepals that are longer than the petals and are sharply pointed at their tips; a 4-12 mm long corolla with five white or pale cream-colored petals, a yellow throat with a few dark purple lines, the lateral petals bearded on their upper surface, and a 1-1.5 mm long spur; two stamens not visible externally; and a single style enlarged into a hollow, globose stigma. The fruit is a spherical or ellipsoidal three-valved capsule, 5-10 mm long containing 6-75, 1.5 mm long, brown seeds.

Viola

Viola arvensis

wild pansy [Blooms: Jun-?]

Yellow violet is a native perennial, the only yellow violet species in Jackson Park (indeed, in all of Illinois). One or more stems arise from an axil of a stem leaf; they are up to 6" tall with a single 3/4" long flower at their tips. Each flower consists of five light green sepals, five yellow petals, five stamens, and a single style; the stamens and style cannot be seen from the exterior. On the lower petal, the flowers have purple lines (nectar guides) and a spur reduced to a small pouch. The two lower, lateral petals have small tufts of hair that obscure the throat of the flower and hide the stamens and style; the two upper, lateral petals are beardless and have only faint lines (nectar guides), if any. The fruit of this species is a bullet-shaped (hairless in the Jackson Park forms) capsule nestled in the calyx with the remnant of the style at its tip, initially green but turning brown as it matures; it ultimately splits along three suture lines to fling the seeds away from the plant.

Viola

Viola pubescens

yellow violet [Blooms: Apr-May]

Riverbank grape's flowers develop in 5" long, drooping, cylindrical or pyramidal panicles opposite the leaves of new branches (but skipping every third leaf). The flowers are greenish-yellow and are best described as skeletal; they may be either unisexual or (rarely) perfect (both male and female reproductive organs functional). The male and female unisexual flowers usually both occur on the same plant, either in separate or mixed clusters; both male and female flowers are 1/8" across or less, with a minute calyx and five green to yellowish petals that quickly fall off. Male flowers have five very long, pale, erect stamens around a button-like center; female flowers have an ovary with a short style and five short, sterile stamens, often contorted. The fruit are .... grapes — a round berry, 1/4-1/2" across containing 1-4 seeds, initially green but turning blue-black as it matures, often with a white bloom on the skin. You know, grapes. The fruit of riverside grape is often sour until after a frost, then becomes more "sweet/tart" to the tongue. Riverside grape is subject to parasitism by the grape filbert gall midge (Ampelomyia vitiscoryloides), an insect whose larvae produce large, very hairy, conical galls at leaf nodes. This gall midge is restricted to the eastern half of North America; it was first described by Alpheus Spring Packard, Jr. in 1869.

Vitis

Vitis riparia

riverbank grape [Blooms: [May-Jun]

American wisteria's flowers occur in showy terminal racemes. The flowers have 1/2" long pedicels that are densely covered with stiff hairs and some club-shaped, stalked glands. Individual flowers consist of a 1/4-3/8"white to pale green, hairy calyx and 15-20 mm long bluish-purple, pea-like, hairless flowers. The expanded portion of the banner (or standard) is bent backwards so it is perpendicular to the axis of the rest of the flower; the two lateral petals cover the keel like a hood. There are 10 stamens with tiny anthers, an ovary encircled by a nectar gland, and a single style hidden within the keel; nine of the 10 stamens are fused to each other, the tenth is free. The fruits are 2.75-4" long pea-like, hairless green pods containing 4-8 kidney-shaped or oval seeds, each about 8 mm wide; the pods are brown and the seeds are black when mature. The seeds contain an alpha-amino acid called canavanine which is structurally similar to L-arginine and the pods contain a saponin called wisterin; neither is a good thing to ingest. I've only seen American wisteria growing on the fence west of Japanese Garden. Periodically, the Park District cuts it down, I suspect because they fear for the fence's structural integrity (it's a heavy plant), but I wish a better solution could be found given American wisteria's rarity.

Wisteria

Wisteria frutescens

American wisteria [Blooms: May-Oct]

Common cocklebur produces a spike-like raceme of compound flowerheads, shorter than the leaf petioles, that arises from the axils of each upper leaf and from the tip of the central stem. Each raceme produces exclusively male flowerheads in its upper parts and exclusively female flowerheads in the lower regions. The male flowerheads are about 1/4-3/4" across, elevated on a short pedicel on top of 1-3 series of white floral bracts. Each of the approximately 20 tiny, brownish-green staminate florets (nominally disk florets) consist of a tubular 1-2 mm long corolla; a minute, non-functional ovary; and five stamens with fused filaments (like a tree trunk) but with their white anthers free, positioned in a ring like a little palm tree or, possibly, a hand. The staminate florets quickly shed their pollen and drop off. The female flowerheads (also nominally disk florets) are 3/4-1.5" long and two-thirds as wide, stalkless, each (usually) containing two female florets nearly enclosed by floral bracts covered with curly white hairs that have a bur-like appearance from the dense, hooked prickles covering their surface. At the tip of the flowerhead are two spines, longer and much stouter than the prickles, each with a hole from which protrudes the divided style of a female floret. There is no corolla in the female florets. The florets are wind pollinated, and their styles quickly wither away after fertilization. Each female floret produces a single, oblong, dark gray to black seed 3/8-1/2" long, tapering to a point at each end and covered by dark membranes, all buried in the bur-like bract. The female flowerhead stiffens through the autumn, turns brown, and overwinters. The seeds are highly poisonous, containing toxic diterpene glycosides. One of the contained seeds germinates the following year; the other delays germination for two years. Common cocklebur prefers wet, sandy soils.

Xanthium

Xanthium strumarium

common cocklebur [Blooms: Sep-?]

The tips of the upper stems of heartleaf alexanders produce 2-3" wide compound umbels of 7-15 umbellets, each with 10-20 tiny yellow flowers. The central flower of each umbellet is sessile; the rest have short pedicels (a diagnostic character of the genus). Each 1/8" wide flower consists of five yellow petals that remain curled, five stamens with yellow anthers projecting through the spaces between the petals, and two styles. The fruits are a ribbed capsule with a flat top from which the remnants of the styles project. Heartleaf alexanders is restricted to northeastern Illinois, where it is uncommon; it is usually found in drier habitats than its much more common relative, golden alexanders (Zizia aurea).

Zizia

Zizia aptera

heartleaf alexanders [Blooms: Apr/May–?]

The tips of the upper stems of golden alexanders produce flat to slightly rounded compound umbels 2-3" across with about a dozen umbellets of tiny, golden-yellow flowers. Each umbellet has about 20 flowers; the central flower is sessile (or nearly sessile) while all the other blooms in the umbellet are on short stalks (pedicels), a character of the genus. Each 1/8" wide flower consists of an insignificant calyx, five yellow petals that are persistently incurled, five stamens with yellow anthers projecting through the spaces between the petals, and two styles. The fruits are a ribbed (not winged) 2 mm long capsule with a flat top from which the remnants of the two styles project. Golden alexanders prefers full to partial sun and is tolerant of a range of habitat quality. The yellow-flowered variety of meadow parsnip (Thaspium trifoliatum var. aureum) is very similar to golden alexanders but has basal leaves that are simple rather than trifoliate compound, but I have not seen meadow parsnip in Jackson Park. John Hilty (www.illinoiswildflowers.info) warns that "Golden Alexanders should not be confused with Pastinaca sativa (Wild Parsnip), which is a weedy Eurasian biennial. The latter is taller, blooms later, and has more leaflets in each compound leaf." Wild parsnip DOES occur in Jackson Park, but it is relatively rare, twice the size of golden alexanders, has robust, strongly ribbed stems, and a large, flattened, winged fruit. Heartleaf alexanders (Zizia aptera) is also very similar, but only the uppermost leaves are compound; all the lower and middle leaves are simple and heart-shaped.

Zizia

Zizia aurea

golden alexanders [Blooms: Apr/May–?]