Park Wildflower Identification Aid 

I have grouped plants by flower color, starting with reds and pinks; then yellows; on to blues. At the end are plants that hide their flowers, such as Jack-in-the-pulpit. 
I have tried for accurate descriptions using both books and the internet as references. If I have misidentified an image, please let me know so I can update this page. 

Toadshade
Trillium sessile

Flowers: Maroon to brownish; three upright petals.
Leaves: Oval, mottled; three at base of flower; atop erect stem. 
Size: 4 - 12 inches tall. 
Habitat: Rich woods. 
Blooms: April - May. 

Rose
Rosa

Flowers: Pink, pale to deep; 5 petals.
Leaves: Oval, toothed,  3 compound leaflets on thorny stems. 
Size: 4 - 6 feet tall. 
Habitat: Woodland thickets, prairies. 
Blooms: June - July.

Spring Beauty
Claytonica virginica

Flowers: Pink to white with thin, dark pink stripes; loose clusters.
Leaves: Grass-like, two per stem. 
Size: 2 - 10 inches tall. 
Habitat: Woods, meadows, streambanks. 
Blooms: March - June

Teasel
Dipsacus sylvestris

Flowers: Purple, tubular, around oval heads atop spiny stems.
Leaves: Lance-shaped pairs; spiny
Size: 2 - 6 feet tall. 
Habitat: Fields, ditches, wastelands.
Blooms: July - October. 

Trout Lily
Erythronium americanum

Flowers: Yellow; six upswept petals atop leafless stalk. 
Leaves: Mottled, leathery; arising from base of the stalk. 
Size: 4 - 12 inches tall. 
Habitat: Moist woods, meadows, bottomlands. 
Blooms: May - June. 

Blue Phlox
Phlox divaricata

Flowers: Light blue with five petals; clusters.
Leaves: Slender, tapered; in pairs along stem. 
Size: 6 - 20 inches tall. 
Habitat: Rich woods, clearings, fields, bluffs. 
Blooms: April - June

Wild Hyacinth
Camassia scilloides

Flowers: Pale blue, star-like clusters atop a leafless stem.
Leaves: Grass-like, radiating from the base of the stem. 
Size: 8 - 24 inches tall. 
Habitat: Open woods, moist meadows, prairies. 
Blooms: April - June. 

Common Blue Violet
Viola sororia

Flowers: Purple, lavender, or white. 
Leaves: Heart-shaped, toothed; at base of plant.
Size: 3 - 12 inches tall.
Habitat: Woods, meadows, lawns, swamps, waste ground.
Blooms: March - June.

Bloodroot
Sanguinaria canadensis

Flowers: White, gold centers atop a single stem, backed by its leaf.
Leaves: Fan-shaped; provided backdrop for bloom. 
Size: 2 - 8 inches tall. 
Habitat: Rich woods.
Blooms: March - May. 

Dutchman's Breeches
Dicentra cucullaria

Flowers: White, waxy, slightly V-shaped.
Leaves: Lacy, fringed; arising from stem base.
Size: 4 - 12 inces tall.
Habitat: Rich woods, shaded moist ledges.
Blooms: April - May.

Large While Trillium
Trillium grandiflorium

Flowers: White; three ruffled petals; atop three whorled leaves.
Leaves: Oval, pointed tip; just below flower; atop leafless stem. 
Size: 8 - 20 inches tall. 
Habitat: Rich woods, thickets. 
Blooms: April - May. 

Mayapple
Podophyllum peltatum

Flowers: White, cup-shaped; under two large "umbrella" leaves.
Leaves: Large, shiny, deeply lobed.
Size: 6 - 20 inches.
Habitat: Rich woods, clearings. 
Blooms: April - June.

Queen Anne's Lace
Daucus carota

Flowers: Flat white clusters atop green feathery collars.
Leaves: Fernlike, alternating along hairy stems. 
Size: 1 - 5 feet tall. 
Habitat: Open woods, fields, meadows.
Blooms: May - October. 

Solomon's Zigzag
Smilacina racemosa

Flowers: White, starlike; clustered at tip of zigzag stem. 
Leaves: Pointed ovals, alternating along stem. 
Size: 1 - 3 feet tall. 
Habitat: Rich woods.
Blooms: March - July

Virginia Waterleaf
Hydrophyllum virginianum

Flowers: White, densely clustered balls atop single stems.
Leaves: Mottled, toothy leaflets.
Size: 1 - 3 feet tall.
Habitat: Moist woods, thickets, clearings. 
Blooms: May - August. 

White Dogtooth Violet
Erythronium albidum

Flowers: White; six upswept petals atop leafless stalk. 
Leaves: Mottled, leathery; arising from base of the stalk. 
Size: 4 - 12 inches tall.
Habitat: Moist woods, thickets. 
Blooms: April - June. 

Woodland Hyacinth
Hyacinthoides hispanica

Flowers: White, pale blue; bell shaped; loose cluster on single stem.
Leaves: Grass-like.
Size: 10 - 12 inches tall. 
Habitat: Woodlands. 
Blooms: May - June. 

Jack-in-the-pulpit
Arisaema triphyllum

Flowers: Hidden within purple and green striped hooded spathe.
Leaves: Three oval leaflets atop an upright stem.
Size: 1 - 3 feet tall. 
Habitat: Moist woods.
Blooms: April - May.