The Lilac (Syringa vulgaris) is a small tree or shrub that is native to southeast Europe but is cultivated in many regions of the world. It is valued as an ornamental plant for its beautiful flowers and for the fragrance that the flowers emit when in bloom. These images were taken in Spain in Madrid (the white cultivar) and in Malaga (the lilac colored flowers).
My roots herald from the city of Spokane Washington which is known as the "Lilac city". Every May there is a week long "Lilac Festival" with many activities including the "Armed Forces Torchlight Parade".
There are many cultivars (varieties within the species or crosses between two related species) of Lilac that have different colored flowers. These white colored flowers come from the "Alba" cultivar. I found this particular tree in the "Retiro" park on downtown Madrid.
The leaves of the Lilac are simple with a "cordate" shape and grow opposite on the branch. They are about 3-4 inches long.
Lilacs tend to grow with multiple stems although with diligent pruning you can keep the plant from to just one main stem. As you can see in the image below this Lilac has about 5-6 intertwined stems.