Japanese Tree Lilac, or Syringa reticulata, is in bloom:
The above is a pretty typical scene for Sarah Roosevelt Park in the early morning hours. Almost all year long, the neighborhood ladies spend the morning on the basketball courts, doing Tai Chi.
The blossom on Syringa reticulata:
It was quite overcast the morning I took this, so it was difficult to get a focused shot, without the flash. As you can see, the actual flowers are much smaller and less tubular than a common lilac. They also lack the fragrance of Syringa vulgaris or S. patula, etc.. Still, their summer blossoms and general toughness mean that municipalities are using them more and more as street trees. Reticulata refers to the reticulate (ridged) undersides of the leaves.