Chicory (Cichorium intybus)

Asteraceae or Sunflower Family
 

Small to medium plant with tattered-looking, dandelion-like leaves and blue (rarely white) flowers.  The "petals" (actually one-petaled ray flowers) have 5 teeth at the tip.  Blooms in summer, the flowers opening in the cool of the morning and closing as the day heats up.

A common weed from Eurasia.  Common in disturbed areas, especially near the main entrance to the park.

True blue is an unusual color for flowers, so chicory is easily recognized.