Showing 37–54 of 372 results

Filtered (44)
Yellow mustard produces inflorescences at the apices of the stems; individual flowers are 3/8" across with four yellowish-green sepals, four yellow petals, six stamens with yellow anthers, and a single pistil with a robust style.

Barbarea

Barbarea vulgaris

yellow rocket [Blooms: Apr-May]

River birch male (left) and female (right) catkins. Individual (highly modified) flowers are distributed over the surface of the catkins.

Betula

Betula nigra

river birch [Blooms: Apr-Jun]

The flowers of devil's beggars-tick consist only of disc florets. The base of the flowerhead is surrounded by 6-10 (usually eight) long phyllaries that extend beyond the flower's edge.

Bidens

Bidens frondosa

devil's beggar-tick [Blooms: Aug-Oct]

In black mustard, racemes of yellow flowers arise from the tip of the stems, with the siliques (fruit) of previously fertilized flowers arrayed along the stem below the flowers. The racemes of flowers are 1/2-2" long. Each flower is about 1/3" (8 mm) across, consisting of a short (2-4 mm) pedicel, 4 sepals (green in the buds, turning yellow after the flower opens), 4 yellow, oval to round petals with a narrow base ("claw"), 6 greenish-yellow stamens with yellow anthers, and a green ovary with a short style (which persists in the siliques) at its apex. Fertilized flowers produce smooth, elongate fruits (siliques) 2-3 mm across, approximately four-angled in section, and 1/2-1" long, tapering to a conical or cylindrical beak with the remnant of the style at its tip. The siliques contain 4-15 seeds and are often closely appressed to the stem. The seeds are dark brown or black with networks of furrows on their surface.

Brassica

Brassica nigra

black mustard [Blooms: Jun-Jul]

Individual flowerheads of false boneset are about a half inch long and surrounded by green phyllaries. Each floret (inset) consists of 7-21 creamy-white, tubular florets with five lobes at the tip, and a prominent divided style protruding from the corolla.

Brickellia

Brickellia eupatorioides

false boneset [Blooms: Jul-Aug]

American searocket's flowers are 3/8" across with four green sepals, four widely spread pale lavender to white petals, six stamens, and a pistil with a single white style.

Cakile

Cakile edentula

American searocket [Blooms: Jun-Aug]

Purple poppy-mallow has hairy flower pedicels ~6" long that arise from leaf axils; the flowers are ~2" across, brilliant magenta, with an hibiscus-like (but shorter) white central structure containing the stamens and styles. The five calyx lobes are very hairy, shorter than the petals, and light green; beneath the calyx are three very similar bracts.

Callirhoe

Callirhoe involucrata

purple poppy-mallow [Blooms: ?-Jul]

The flowers of hedge bindweed are 2-3" long, formed from five white or pink fused petals; the throat of the trumpet is light yellow (less extensive than in field bindweed). The flowers are ephemeral, often lasting only a single day.

Calystegia

Calystegia sepium

hedge bindweed [Blooms: May-Sep]

American bellflower has deep blue flowers with a white center; they are about 1" across. The petals are ruffled, the style is long, arching, with a trifid stigma on its tip.

Campanula

Campanula americana

American bellflower [Blooms: Jul-Aug]

Creeping bellflower stems produce a terminal raceme of blue to purple flowers up to a foot long with all the flowers nodding towards the ground and all on the same side of the stem. Individual flowers are 1-1.5" long, borne on a short pedicel with a narrow, lance-shaped bract at its base. Each flower is bell-shaped with five pointed, recurved lobes with hairy margins and five green sepals at its base. There are 5 short curly, yellow stamens and a long style that emerges from the bell; the style has a three-part stigma at its end.

Campanula

Campanula rapunculoides

creeping bellflower [Blooms: Aug-Sep]

Shepard's purse flowers bloom only at the stem's tip, which is continually elongating. Individual flowers are tiny (1/8") and have 4 greenish sepals, 4 rounded white petals, 6 greenish-yellow stamens, and a pistil with a single style. Flowers are followed by seedpods ("purses") that are 1/4" long, triangular, or heart-shaped, borne on ascending pedicels (lower part of image.)

Capsella

Capsella bursa-pastoris

shepard's purse [Blooms: Apr-May]

Hairy bittercress flower stalks with stem leaves. Here the three flowers bear seedpods (siliques - narrow cylinders) that elongate directly out of fertilized flowers (which continue bear petals).

Cardamine

Cardamine hirsuta

hairy bitter-cress [Blooms: April]

Pennsylvania bittercress flowers are 1/8" across with 4 light green, oblong sepals that cup the corolla, 4 white petals, 6 cream-colored stamens, and a single robust pistil with a flat, disc-shaped stigma. Fruits are erect, elongate (up to 1.25" long and 1 mm wide), flat-ended cylinders (siliques) containing a single row of seeds that emerge from the center of a fertilized flower while the petals persist.

Cardamine

Cardamine pensylvanica

Pennsylvania bitter-cress [Blooms: April]

Nodding thistle is another heavily-defended exotic thistle, accidentally introduced to the U.S in the early 1900s. Solitary flowerheads are borne on long (up to 2'), whitish peduncles densely covered with short hairs. The flowerheads are 1-3" across, nodding (like the name says), made of 100-1000 tubular disk florets, each with its apical portion divided into 5 purplish-pink filaments and with a single, very long style. Beneath the large, showy flowerheads are stout, triangular, purplish phyllaries, each with a stout spine. When in bloom, the large size of the flowers and characteristic large phyllaries make it impossible to confuse with any of our other local thistles. Well loved by goldfinches, but considered a "noxious weed" by almost everyone else.

Carduus

Carduus nutans

nodding thistle [Blooms: Jun-Jul]

Inflorescences of woodland sedge occur as a terminal staminate (male) spike 6-12 mm long and 2-4 ovoid pistillate (female) spikelets 10-20 mm long and 5 mm wide that are lower on the culm. The proximal urn-shaped structures on the inflorescence (and in the inset) with the two fuzzy filaments are the pistillate spikelets; the distal structures with the terminal yellow rods in the image are the staminate spikelets. (Cylindrical clusters of florets are called spikes; ovoid clusters are termed spikelets. Individual sedge flowers — a perigynium or utricle — are usually ovoid, with either 2-3 feathery stigmas or three stamens with anthers sticking out of one end. Bisexual flowers do not occur in sedges.)

Carex

Carex blanda

woodland sedge [Blooms: Apr-May]

Capitate sedge grows 1-2' tall in dense colonies. Each culm (= stem) is triangular in cross section and has an inflorescence about 1.5 cm. long and 1.0 cm. across at its tip. At the base of the inflorescence is a thin leaf (bract) up to 1.5 cm. long. The inflorescence looks like a collection of 5-8 spikey, tightly-clustered tapering stacks (spikelets) of flattened, oval structures sharply pointed at their distal end (the perigynia or florets). Each spikelet measures about 5x5 mm; it contains the actual (highly modified) florets. The male (staminate) florets are located toward the apex of each spikelet (see inflorescence at far left in the image), while the female (pistillate) florets are lower in the spikelet. (Cylindrical clusters of florets are called spikes; ovoid clusters are termed spikelets. Individual sedge flowers — a perigynium or utricle — are usually ovoid, with either 2-3 feathery stigmas or 3 stamens with anthers sticking out of one end. Bisexual flowers do not occur in sedges.)

Carex

Carex cephalophora

capitate sedge [Blooms: May-Jun]

Bottlebrush sedge's fertile stems bear a single, terminal staminate (male) spike up to 3" long and 2-6 pistillate (female) spikes (shown here), each 5-6 cm long and 1.5 cm across. The cylindrical pistillate spikes are comprised of densely packed, female perigynia (florets) radiating from the center of the cylinder.

Carex

Carex comosa

bottlebrush sedge [Blooms: May-Jun]

Gray's sedge is the most easily identifiable sedge in Jackson Park — the large, pistillate (female) spikelet (reminiscent of the head of a medieval mace) is unmistakable. Fertile culms of Gray's sedge may reach up to 3' tall, but most plants don't exceed 2.5'. The culms are triangular in section ("three-angled"), light green and unbranched, with a few alternate, dark green leaves (each 5-14" long and 4-10 mm wide) along its length. The leaves have a deep groove along their midline and, usually, secondary folds on either side, producing a V- or W-shaped cross section in the leaves. Fertile culms produce an Inflorescence at their apex consisting of one or more globoid (mace-like) pistillate spikelets (1-1.5' diameter spiky clusters of perigynia that radiate in all directions) and a single staminate spikelet up to 2.5" long and 1-4 mm wide. Each pistillate spikelet has a 3-10" long leaf at its base. Each perigynum in the pistillate spikelets is quite large (12-18 mm long, 4-8 mm wide), an elongate teardrop (lanceolate) shape, with stigmas emerging from the pointed end. The staminate spikelet is at the tip of the culm on the end of a short pedicle, usually yellow-brown in color. The male and female spikelets are labeled; the long, tan-colored anthers (male) and white stigmas (female) are clearly visible in this image.

Carex

Carex grayi

Gray's sedge [Blooms: May-Jul]