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Hedge mustard flowers occur at the tips of long, slender flower stalks that curve upward; the flower stalks typically arise in abundance at the top of the plant. Each flower is small (1/4" across) with four greenish-yellow sepals, four rectangular yellow petals with rounded tips, a single stout style, and six stamens. The fruit is a very slender, cylindrical seedpod (silique) lower on the flower stalk than the blooming flowers; the siliques are 3/8-3/4" long, erect, oriented parallel to and often appressed to the flower stalk, with the remains of the style on their tips. The siliques turn light brown when mature and split open to release the seeds. The short (<3/4"), straight, appressed seedpods and the upward-curving, sparse flower stalks with only a few blooms open at any one time distinguish hedge mustard from other local mustards.

Sisymbrium

Sisymbrium officinale

hedge mustard [Blooms: May-Jul]

The axils of the middle and upper leaves of woodland goldenrod produce small clusters of 1-12 flowerheads; the stem tip may also develop a small (3" long, 1.5" across) panicle of flowerheads. Individual flowerheads are tiny (3 mm) consisting of 4-5 ray florets with yellow, oblong-elliptical "petals" and 3-6 disc florets with golden yellow, tubular corollas with five tiny lobes. At the base of each flowerhead are three overlapping series of light green, elongate-elliptical bracts (phyllaries). The fruit is a small, bullet-shaped seed 1-2 mm long with a tuft of white hairs 3-5 mm long. In Illinois, only woodland goldenrod and broad-leafed goldenrod (Solidago flexicaulis) produce clusters of flowerheads from the axils of the middle and upper leaves; however, the latter has coarsely serrated leaves with petioles and should be easy to distinguish from woodland goldenrod.

Solidago

Solidago caesia

woodland goldenrod [Blooms: Sep-Oct]

The tip of broad-leaved goldenrod's stem produces a cylindrical inflorescence (a raceme or a narrow panicle) 1.5-5" long and about a third as wide; smaller racemes (1/2-1.5" long, smaller than the leaves) arise from the axils of the upper leaves. Individual flowerheads are about 1/4" across with 3-4 yellow ray florets asymmetrically deployed around the flowerhead and 4-8 yellow disk florets. The base of the flowerhead is surrounded by 3-5 series of unequal, narrowly oblong, light green phyllaries; the outermost phyllaries are 1-2 mm long while the innermost are 3.7-4.7 mm long. Broad-leaved goldenrod prefers high-quality, moist, shaded woodlands. In Illinois, only broad-leaved goldenrod and woodland goldenrod (Solidago caesia) produce clusters of flowerheads from the axils of the middle and upper leaves. Broad-leaved goldenrod has unusually large flowers for a goldenrod and the ray florets are not evenly distributed around the flowerhead. In addition, woodland goldenrod has smooth or finely serrated leaf margins (rather than coarsely-toothed leaves) and no petioles (the leaves are sessile) — it should be easy to distinguish from broad-leaved goldenrod.

Solidago

Solidago flexicaulis

broad-leaved goldenrod [Blooms: Jul-Sep]

Early goldenrod's inflorescence is apical, a panicle of flowering stems that "often arch upward and outward like a fireworks display" (John Hilty, www.illinoiswildflowers.info). Individual flowerheads are about 1/4" across; they have 4-12 yellow ray florets, not all open at one time, and 8-15 yellow disk florets. The base of the flowerhead is surrounded by 3-4 series of overlapping, narrow, hairless, yellowish-green bracts (phyllaries) that together are 3-4 mm (1/16") long. The pedicels (flower stalks) are usually hairless, all attached on one side of the panicle's flowering branches and curving upward. The fruit is a cone-shaped dry seed 1-1.5 mm long with an attached tuft of light brown hairs 2.5-3.5 mm long. The combination of wing-like leaflets in the leaf axils, hairless stems and leaves, and an inflorescence whose flowering stems flare up and out is diagnostic for early goldenrod. Field goldenrod (Solidago nemoralis) is much the same size and general appearance, but has hairy stems and leaves, unlike early goldenrod.

Solidago

Solidago juncea

early goldenrod [Blooms: Jul/Aug-?]

The wand-shaped, nodding inflorescence of field goldenrod arises from the tip of the stem; it is 3-7" long and widest in the middle, tapering towards either end; the flowerheads are all on one side of the flower branches. Flowerheads are each 1/4" across consisting of 4-10 yellow ray florets and 3-10 yellow disk florets. The bracts (phyllaries) surrounding the base of the flowerhead are in three overlapping series; they are pale greenish yellow, covered in short, white hairs. The fruit is a dry seed 0.5-2 mm long with an attached tuft of light brown hairs. Field goldenrod can be distinguished from other goldenrods by (1) its diminutive size, (2) the inflorescence that nods to one size, (3) leaflets present in leaf axils (4) short, fine hairs on both leaves and stems, and (5) the grayish cast of the leaves.

Solidago

Solidago nemoralis

field goldenrod [Blooms: Aug-Oct]

Showy goldenrod's inflorescence is a showy, cylindrical panicle up to 12" long arising from the tip of the stem; the flowering stems are erect or curve upwards and the flowerheads occur on all sides of the flowering stems. (Unlike most goldenrods, where the flowering stems curve outward and downward and the flowerheads are on one side of the flowering stems.) Each flowerhead is about 1/4" across consisting of 4-10 large (for a goldenrod) pistillate ray florets (no stamens) and 6-16 perfect disk florets (both stamens and style). Behind the flowerhead are 3-4 series of overlapping bracts (phyllaries), each with a prominent midvein. The fruit is a 2 mm long seed with dark brown longitudinal grooves and a tuft of light brown hairs. Showy goldenrod is distinguished from other goldenrods by the character combination of: (1) stem leaf margins smooth (not toothed), (2) wing-like leaflets in axils of upper leaves, (3) the stems of the inflorescence erect or curve upward (not out and down), and (4) stems and leaves largely or completely hairless except in the inflorescence.

Solidago

Solidago speciosa

showy goldenrod [Blooms: Jul-Oct]

Elmleaf goldenrod's stem (and sometimes upper leaf axils) produces an open, airy inflorescence (a panicle) at its tip that may be a foot tall and wide with arching, widely-spreading branches. The flowerheads rest on very short stems (nearly sessile) along one side of the major branches, facing upward; on the opposite side of the branches are small (1") bracts. Both stems and branches in the inflorescence are covered with hairs. The flowerheads are 1/8-1/4" across with 3-6 yellow, pistillate ray florets (no stamens) and 4-7 yellow, perfect disk florets (both stamens and a style). Surrounding the base of the flowerheads are 16-18 bracts (phyllaries) in 2-3 overlapping series.

Solidago

Solidago ulmifolia

elmleaf goldenrod [Blooms: Jul-Oct]

Purple meadow-rue is a native perennial that is listed as "vulnerable" in Illinois. The species is found in most of the lower 48 states in the U.S. but is notably absent from states on the Atlantic and Pacific coasts (however, it is present along the Gulf of Mexico). Purple meadow-rue is dioecious — some plants produce only staminate (male) flowers, each with around a dozen stamens; other plants bear only pistillate (female) flowers, each with about ten pistils. The male flowers are the showier of the two. Petals are absent (the plant is wind-pollinated). Both the narrow, whitish-grey, thread-like pistils and the yellow-green stamens (with pale yellow anthers) droop from 4-5 light green sepals (that may drop off). Fertilized female flowers develop a single, spindle-shaped fruit that is 1/4" long, elongated, sharply pointed with a remnant style, 4-6 raised ribs, and slightly concave along one side. The fruit is initially green, turning brown with maturity. Early meadow-rue (Thalictrum dioicum) is similar to purple meadow-rue but has light purplish-green stems and leaves with 3-9 (typically five) rounded lobes and long petioles on the upper leaves.

Thalictrum

Thalictrum dasycarpum

purple meadow-rue [Blooms: May-Jun]

Early meadow-rue's main stem terminates in a panicle up to a foot long and wide; each branch in the panicle has a corymb of about five flowers at its tip. Early meadow-rue is dioecious — some plants produce only staminate (male) flowers, each with 10+ stamens; other plants bear only pistillate (female) flowers, each with up to 15 pistils. Both male and female flowers droop from their stems, but the male flowers have a longer droop than do the female flowers. Both male and female flowers are about 1/2" long and 1/4" across with 4-5 pale green sepals with white margins (which often fall off). Neither male nor female flowers have petals; pollination is via the wind. Fertilized female flowers produce ellipsoid, dry seeds that are pointed at both ends; the surface bears strong ribbing. Early meadow-rue prefers shady woodlands. It has more lobes on its leaves (usually 3-5), and the lobes are more rounded than purple meadow-rue (Thalictrum dasycarpum), the other Thalictrum species in Jackson Park, does (2-3 pointed lobes).

Thalictrum

Thalictrum dioicum

early meadow-rue [Blooms: Apr-May]

Field pennycress's central stem and the upper side stems produce racemes of flowers at their tips. The flowers bloom at the tip of the raceme, which continues to elongate to 3-8" long and to produce new buds; the prominent, disk-shaped fruits develop lower on the raceme. Individual flowers are about 1/8-1/4" across on a 1/2" pedicel; there are four green sepals with whitish edges, four white, oval petals, six yellowish-green stamens (three on each side of the flattened ovary), and a single short style. The fruit is a 1/2" wide flattened, winged disc with a distinct U-shaped notch at the apex; the fruits are borne on the flower pedicels, which spread perpendicular to the stem. Each seedpod has two compartments, each compartment containing several dark brown seeds. Other mustards have long, cylindrical seedpods; the nearly-circular seedpod of field pennycress is unique among Jackson Park mustards. Young field pennycress plants are edible but become very bitter at flowering. Cows that feed on field pennycress produce "tainted" milk that tastes like garlic.

Thlaspi

Thlaspi arvense

field pennycress [Blooms: Apr-Jun]

Slender stinging nettle plants are dioecious (unisexual) with male (staminate) and female (pistillate) flowers on separate plants. Flowers occur in knobby clusters (panicles) that arise from the leaf axils. Neither pistillate nor staminate flowers have any petals. Staminate flowers have four light green, identical sepals cupping four short stamens. Pistillate flowers also have four sepals but two sepals are narrowly lance-shaped, about a millimeter long, and free, alternating with two sepals that are 1.4-1.8 mm long and cupped around the ovary; styles are absent but the single stigma is long and feathery. The fruit is a flattened, oval to egg-shaped, seed less than 1/16" long. Stinging nettles (aka, tall nettle, slender stinging nettle) have a complicated biogeographic history. According to USDA Plants (https://plants.sc.egov.usda.gov/) and ITIS.gov, the subspecies "Urtica dioica gracilis" is native, while the subspecies "Urtica dioica dioica" is an exotic that is native to Europe and Asia. Thus, you may see "stinging nettle" listed as either "native" or "exotic." Both subspecies are perennials, and both occur in Illinois, although "gracilis" is most common; most features are the same for both subspecies. Wikipedia says these subspecies are actually separate species, an opinion based on a 2014 paper in Phytotaxa (162: 61-83) that analyzed molecular characters; Kew Garden's Plants of the World Online (https://powo.science.kew.org/) and iNaturalist also accept Urtica gracilis as a valid species. I've chosen to use "Urtica gracilis" here if only to avoid further proliferation of long scientific names in this presentation.

Urtica

Urtica gracilis

slender stinging nettle [Blooms: Jul-Aug]