This is a small stand of Arizona ash (Fraxinus velutina) at El Dorado Park in Long Beach. It is found in the wild in southern California but also in parks and golf courses.
Fraxinus velutina is a tree in the Oleaceae family that is a good native host of the swallowtails Papilio rutulus and P. multicaudata.
A closer look at the leaves. I feed young larvae the tender, sometimes sticky new leaves from the ends of newer branches.