Asteraceae, the daisy, sunflower, or composite family.
Plant: Variable, erect plant, 2'-5', with prickly-margined leaves, small, yellow flower heads, and narrow, vase-shaped buds. Stems and leaves exude milky sap when broken. Annual or biennial.
Flowers: Yellow heads with all ray flowers, opening 1/4"-1/2", usually 8-20 rays, bud and flower-base narrow and vase-shaped; arranged in an open panicle. Sometimes turning bluish when closed and drying.
Leaves: Alternate, with prickles on the margin, and often on the lower side of the midrib. Variable in shape, from simple obovate to oblanceolate, to lobed; base arrow-shaped and clasping the stem. The leaves sometimes twist vertically to follow the sun, aligning in parallel planes. Stem mostly smooth, sometime with a few prickles.
Fruit: A flat achene with a large, silky "parachute" (pappus).
Habitat: Weedy areas, roadsides, disturbed ground.
This introduced European species is closely related to cultivated lettuce (L. sativa).
It is marginally edible, but has a strong, bitter taste.
The plant is somewhat similar to some of the sow thistles, but is distinguished by the
narrower, vase-shaped buds, and by having fewer rays on the flower heads.
Another colloquial name is Compass Plant, referring to the way the leaves twist to track the sun.
Where to find it:
Not common in the park. I have found it occasionally growing in disturbed, open areas.