There are a few trees that I adore and try to incorporate in my projects when I can, especially gardens in Brooklyn and Manhattan where space is usually limited. These three trees are among my favorites because they are all small in scale, and pack a serious punch in terms of their visual interest, seasonality, and form. They are:
The Redbud tree is a small, resilient deciduous tree that in the Spring has tiny pink flowers that appear to grow right from the twigs and branches before they leaf out. They are absolutely exquisite in early Spring, and then in the late summer their large heart shaped leaves turn golden. They also have a very graceful, rounded form, It's also very undemanding about it's growing conditions, which makes it a welcome addition to any garden.
Serviceberry is a native deciduous ornamental and comes in both tree and shrub form, and there are many varieties to choose from. They are low maintenance, tolerating various degrees of shade and sun, with small white flowers in spring and yellow to red Fall color. I love their form--they are smallish (3-20' tall) and multi stemmed, and the trunks have a thickness that feels substantial and sculptural. Their versatility makes them great for small urban gardens.
Grey Birch is a deciduous native to the Northeast. It is a fast growing tree that does well with sunlight and moist, well drained soil. What I love about them is their graceful habit and transparent canopy, made up of small delicate heart-shaped leaves, their white bark, and their golden Fall color. Certain species are susceptible to bronze birch borers, so beware...but there are many varieties so check which is suited to your conditions.