Ash-Leaf Maple, or Box Elder, is the only maple in North America with compound leaves. The dangling flowers appear in early spring just as the leaves are beginning to show themselves.
This tree tends to take over hedges in the city, and perhaps the best way to deal with that is just to let it take over. The leaves often have three leaflets, making them easy to mistake for Poison Ivy. This tree grew at the edge of a little park in Beechview.
Gray describes the genus and the species:
ACER [Tourn.] L. MAPLE
Flowers polygamo-dioecious. Calyx colored, 5 (rarely 4-12)-lobed or -parted. Petals either none or as many as the lobes of the calyx, equal, with short claws if any, inserted on the margin of a perigynous or hypogynous disk. Stamens 3-12. Ovary 2-celled, with a pair of ovules in each cell; styles 2, long and slender, united only below, stigmatic down the inside. From the back of each carpel grows a wing, converting the fruit into two 1-seeded at length separable samaras or keys. Trees or sometimes shrubs, with opposite palmately lobed leaves, and small flowers. Pedicels not jointed. (The classical name, from the Celtic ac, hard.)
A. Negundo L. (BOX ELDER.) Leaflets 3-6 (-9), smoothish when old, very veiny, ovate, pointed, toothed; petals none; fruit smooth, with large rather incurved wings. (Negundo aceroides Moench.) River-banks, w. N. E. to Man., south w. and westw.; extensively cultivated and frequently seeding itself eastw. Apr. A small but handsome tree, with light-green twigs, and very delicate drooping clusters of small greenish flowers rather earlier than the leaves.