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The end of green/red amaranthus stem bears a bristly panicle of tiny flowers up to 18" tall; the flowers are either staminate (male) or pistillate (female), but both occur on each plant. The flowers are wind pollinated. Flowers lack petals but have five pink sepals 2 mm long with pointed tips (which, together with associated 3-4 mm long, red bracts, produce the bristly appearance). Male flowers have five stamens while female flowers have a single ovary with three stigmas.

Amaranthus

Amaranthus hybridus

green/red amaranth [Blooms: Sep-?]

At the apex of the stem of Palmer's amaranth is a panicle up to 18" long covered with tiny green flowers that are wind-pollinated. Flowers have 4-5 petals. Individual plants produce either staminate (male) or pistillate (female flowers) but not both; perfect flowers are unknown.

Amaranthus

Amaranthus palmeri

Palmer's amaranth [Blooms: Aug–?]

The tip of the stem of redroot amaranth produces a panicle of greenish-white flowers; smaller panicles of flowers also arise from the axils of the leaves in the upper half of the plant. Both male (staminate) and female (pistillate) flowers appear in the same inflorescence; perfect flowers are absent. Individual flowers lack petals but have 5 white tepals that are about 3 mm long and one or more small (3-6 mm) green, bracts under the flower whose midrib extends to form a spine; male flowers also have 3-5 yellow stamens, while female flowers also have an ovary with a 3-parted style on the top of the ovary.

Amaranthus

Amaranthus retroflexus

redroot amaranth [Blooms: Aug-Oct]

Common ragweed is a highly branched, weedy plant that gets about 3' tall. Numerous stems bear cylindrical flower spikes 1-6" long and 1/4" wide; the flowers are tiny (1/8"), all male (except near the base of the spike) in cup-like involucres that are initially green but turn yellowish-green with age, bead-like, hanging from short stalks. The actual male flowers are hidden in the involucre, lack petals, have numerous yellow anthers and (notoriously) produce copious yellow pollen that is carried by the wind; female flowers are enclosed in leafy bracts with protruding paired white styles, and occur in cryptic clusters on the stems below the flower spikes and in leaf axils. If you suffer from seasonal allergies, this plant and its cousin, giant ragweed, are the culprits, NOT the unfairly maligned goldenrod (which has sticky pollen that never gets airborne). Common ragweed has pinnatifid (pinnate-like) leaves; giant ragweed has deeply-lobed leaves that appear palmate.

Ambrosia

Ambrosia artemisiifolia

common ragweed [Blooms: Aug-?]

Male (staminate) and female (pistillate) flowers are physically separated on Western ragweed plants with the male flowers on spike-like racemes 1-6" long that arise from the upper stems, while female flowers occur more basally in small clusters at the base of the spike, along stems, or from leaf axils. Individual staminate flowerheads occur along the entire length of the spike, facing in all directions. They are 2-5 mm across, drooping from 1-4 mm long peduncles and developing a short, bell-like shape as they mature; they are covered by 3-5 oval, fuzzy phyllaries (bracts) in a single series where the lower half of each phyllary is fused to the other phyllaries. Beneath the phyllaries are approximately four staminate florets, each bearing five stamens with pale yellow anthers. The pistillate flowerheads are egg shaped and occur in clusters with a basal bract up to 1.25" long; pairs of smaller bracts lie just below each individual pistillate flowerhead. Pistillate flowerheads each sit in a cup of fused phyllaries 8 mm long and 3 mm across that has several tooth-like projections; each cup holds a single pistillate floret with a bifurcated style protruding from the apex of the floret. The florets are wind pollinated. Like other Ambrosia species in Jackson Park (common ragweed and giant ragweed), Western ragweed may contribute to hay fever symptoms. Western and common ragweed are similar to each other, but Western ragweed (almost always) has simple-pinnate leaves while common ragweed has double-pinnate leaves that are more deeply lobed and fern-like; Western ragweed is the hairier of the two.

Ambrosia

Ambrosia psilostachya

Western ragweed [Blooms: ?-Nov]

Giant ragweed is a much larger (up to 12' tall) cousin of common ragweed (A. artemisiifolia) but similarly bushy and weedy, with a candelabra-like appearance in the upper parts of the plant. The upper stems bear 3-6" long flower spikes, all male (except near the base of the spike) in 1/8" wide cup-like involucres that are initially green but turn yellowish-green with age, hanging from short stalks. The actual male flowers are hidden in the involucre, lack petals, have numerous yellow anthers and (notoriously) produce copious yellow pollen that is carried by the wind; female flowers are enclosed in leafy bracts with protruding paired white styles, and occur in cryptic clusters on the stems below the flower spikes and in leaf axils. If you suffer from seasonal allergies, this plant and its cousin, common ragweed, are the culprits, NOT the unfairly maligned goldenrod (which has sticky pollen that never gets airborne). Common ragweed has pinnatifid (pinnate-like) leaves; giant ragweed has deeply-lobed leaves that appear palmate.

Ambrosia

Ambrosia trifida

great ragweed [Blooms: Aug-Sep]

Downy serviceberry is a shrub or small tree 10-30' tall that blooms very early in the spring, before (most) leaf emergence; this is the most common Amelanchier sp. in Illinois. Downy serviceberry flowers bloom in a cluster of 5-12 before or early in leaf emergence. (Emerging leaves are folded and bronze-tinged.) Flowers are 1" across with a short, light green, a hairy calyx with five narrow triangular teeth 1/3 the length of the petals that are strongly bent back towards the stem; five narrow, oblong white petals; 15-20 stamens with creamy yellow anthers; a hairless green ovary; and a green pistil with a single five-parted style. Downy serviceberry flowers can be easily distinguished from Wiegand's shadbush (Amelanchier interior); the former has a hairless ovary while the latter has an ovary whose top is densely covered with wooly hairs. The very hairy undersides of downy serviceberry leaves are also a good clue to its identity, although other Amelanchier spp. also have (less) hairy leaves.

Amelanchier

Amelanchier arborea

downy serviceberry [Blooms: Apr-May]

Wiegand's shadbush (aka, serviceberry) is a shrub or small tree up to 10m tall, uncommon in Illinois and restricted to the northeastern portion of the state. The flowers bloom in clusters of 6-12 simultaneously with leaf emergence. (Emerging leaves are folded and bronze-tinged.) The flowers are 1" across with a short, light green, hairy calyx with five narrow triangular teeth 1/3 the length of the petals, strongly bent back towards the stem; five narrow, oblong white petals; 18-20 stamens with creamy yellow anthers; a characteristic green ovary densely hairy on the top; and a green pistil with a single five-parted style. Wiegand's shadbush flowers can be easily distinguished from downy serviceberry (A. arborea); the former has an ovary whose top is densely covered with wooly hairs while the latter has a hairless ovary.

Amelanchier

Amelanchier interior

Wiegand's shadbush [Blooms: Apr-May]

Marram grass forms a culm that remains short (~2") if no inflorescence is produced but reaches heights of 30" with an inflorescence. Culms produce a 6-12" long spike-like panicles of single-flowered spikelets each 9-15 mm long. Flowers are wind-pollinated, as is common in grasses. This plant is endangered in Illinois and is restricted to beaches along the Lake Michigan shoreline where it is often the dominant grass.

Ammophila

Ammophila breviligulata

marram grass [Blooms: Jul-?]

Lead plant is a sprawling bush 1-3' tall. the stems, leaves, flower spikes, and flower calyxes are densely covered with white, wooly hairs (giving the appearance of a metallic surface). The flower spikes are up to 6" long; they arise from the ends of branches. Flowers are 1/4" long, purple with reddish stamens and golden anthers; there is a single petal on the upper side of the flower that is initially tubular but opens after pollination to nearly flat (horizontal). Lead plant is considered an indicator of high-quality habitat; its tap roots can reach up to 5 m long. The flowers of lead plant look like false indigo (Amorpha fruticosa), but the latter is a much larger shrub.

Amorpha

Amorpha canescens

lead plant [Blooms: Jun-Sep]

Sharp-lobed hepatica is an early-blooming, woodland wildflower with distinctive 3-lobed, superficially palmate, variegated basal leaves on long petioles. The flowers are 1" across, borne on naked, reddish, hairy stalks ~4" long. Flowers consists of 5-11 (typically 6) blue, white, or lavender, oblong petals (actually, sepals), copious white stamens, and numerous green carpels; behind the flower are 3 reddish, hairy bracts shorter than the petals. ITIS considers Hepatica acutiloba a junior synonym of Anemone acutiloba; the USDA Plants Database, IUCN Red List, and NatureServe Explorer considers H. acutiloba as a junior synonym of Hepatica nobilis. All agree it is "sharplobed hepatica." The roundlobed hepatica (which is either a variety of sharplobed hepatica or a separate species, depending on which authority you prefer) is identical except that the lobes on the leaves are smoothly rounded.

Anemone

Anemone acutiloba

sharp-lobed hepatica [Blooms: Apr]

The petals (actually, sepals) of Canada anemone flowers are rounded; the pistillate cone in the center of the flower is approximately hemispherical and less than 10% of the flower width. The fruit is a round cluster of flattened seeds. The five-lobed leaves of Canada anemone are superficially similar to those of wild geranium (Geranium maculatum) but are sessile, not borne on petioles. Canada anemone is the commonest flower in Jackson Park in the late spring and summer.

Anemone

Anemone canadensis

Canada anemone [Blooms: May–Oct]

Thmbleweed flowers are borne on long (1-2') stalks; each flower is about 3/4" across with 5 pointed white petals-like sepals that often remain partially closed; the green pistillate cone in the center of the flower is about twice as long as it is wide (i.e., a tall gumdrop) ~20% of the flower diameter. A. canadensis may also have pointed petals, but the cone in the center of the flower is hemispherical (a short gumdrop). Thimbleweed (A. cylindrica) is best distinguished from tall anemone (A. virginiana) by the shape of the leaflets — A. cylindrica has leaflets with a wedge-shaped base with the lobes radiating out from the base, while A. virginiana has a rounded leaflet base with toothed distal margins.

Anemone

Anemone cylindrica

thimbleweed [Blooms: Jun-Jul]

Wood anemone produces slender green, hairy stems that bear either alternate leaves or (more typically) a whorl of three compound leaves at the apex of the stem; the 5 cm tall flower stalk arises from the center of the whorl. The flower stalks each bear a single white (sometimes pink) flower 1" across with 4-9 petal-like sepals and 30-60 stamens with white anthers surrounding numerous simple pistils.

Anemone

Anemone quinquefolia

wood anemone [Blooms: Apr–May]

Tall anemones have leaves on long petioles (like A. cylindrica). The petals (actually, sepals) of the flowers are pointed (like A. cylindrica); the pistillate cone in the center of the flower is approximately hemispherical and >1/3" across, about 20% of flower diameter. Thimbleweed (A. cylindrica) is best distinguished from tall anemone (A. virginiana) by the shape of the leaflets — A. cylindrica has leaflets with a wedge-shaped base with the lobes radiating out from the base while A. virginiana has a rounded leaflet base with toothed distal margins.

Anemone

Anemone virginiana

tall anemone [Blooms: Jun–?]

Field pussytoes flowerheads are either pistillate (female) or staminate (male), both about 8 mm long, both looking like a compact tuft of white hairs. The very similar plantain-leafed pussytoes (A. plantaginifolia) looks much the same but has basal leaves with three main veins (best viewed from the underside) rather than one.

Antennaria

Antennaria neglecta

field pussytoes [Blooms: Apr-May]

Plantain-leafed pussytoes is a short (6" tall) plant. The basal leaves are 2" wide and 3.5" long, spoon-shaped with long petioles, grayish green, with 3-5 conspicuous main veins; the lower surface is densely covered with appressed hairs and is shiny white. Individual plantain-leafed pussytoe plants bear either male or female flowers exclusively. Flowerheads are short (<1/2" long) and composed exclusively of white disc florets surrounded by a layer of phyllaries; female florets are fluffy white from the profusion of styles (looking a bit like Q-Tips) while male florets show tubular, brownish anthers. Asexual reproduction may produce colonies of exclusively male or female plants. The similar field pussytoes has basal leaves with only a single (rather than 3-5) main veins.

Antennaria

Antennaria plantaginifolia

plaintain-leafed pussytoes [Blooms: Apr-May]

The main stems and some of the lateral branches of dogbane produce panicles of flowers 1-3" across on their tips; the central flowers in the cluster open first. Individual flowers are tiny — 2-3 mm across and 3-5 mm long, bell-shaped, with a fluted edge produced by the 5 white pointed petals. The stamens are shorter than the petals and curve toward the center of the flower, forming a cone over the ovoid stigma.

Apocynum

Apocynum cannabinum

common dogbane [Blooms: Jun-Aug]