Double Pink Cherry
Prunus serrulata 'Kwanzan'
There are three double pink cherry trees in the Park. See Wikipedia entry here.
The Kwanzan cherry has double pink flowers and a vase-shaped form with a rounded crown that spreads with age, making the tree wider than it is tall at maturity. The new leaves are bronze-colored, turning to dark green, then yellow, orange, or copper in the fall. This is a fruitless cultivar.
Cherry in the northwest corner of the Park in April
Double pink cherry tree factoids:
The cherries are probably the easiest to identify with their multi-petaled flowers in the spring, their dark green serrated leaves in the summer, and their smooth purplish bark year round.
A wild cherry has five petals in the flower, but breeding has led to cherries like ours with up to 28 petals in each flower
The ornamental cherry trees are bred for their showy flowers, and most do not bear fruit.
In Japanese culture, the cherry blossoms, which only last about a week on each tree, signify the ephemeral. The dead cherry trees bordering the Park on 19th Street also seem ephemeral.
Cherry tree bark from the other cherry in the northwest triangle, next to the flowering cherry in the photo above
The horizontal lines on the bark are called lenticels, and they permit direct exchange of gases between the atmosphere and the interior of the tree.
Cherry in southeast triangle in April, looking east, with the boughs drooping with the weight of the flowers
Cherry in the northwest triangle in July with characteristic bark and leaves
The leaf on the left is showing its glossy deep green upper surface. The leaf on the right shows the matte lighter green undersurface.
Botany 101 Bonus
There are many physical attributes to examine to identify a tree, and there are many dichotomous tree identification algorithms on the internet. One can look at tree shape; deciduous versus evergreen; flowering versus not; leaf attachments to the branches; bark; and fruit appearance and ripening season. The chart below gives terminology in describing the leaf shape, edge, and vein pattern. Of course, Nature doesn't shoehorn herself into our exact descriptive categories, but the cherry leaf can be described as ovate-acuminate in shape, serrate on the edges, and pinnate-arcuate as far as venation.