The trees should be selected with reference to their adaptability to the soil and also to the width of the street and its character. A broad, winding boulevard will be best suited to large varieties like the oriental plane, rock maple and linden, or to trees of spreading habit like the American elm. Straight and narrow streets will look best lined with more compact and formal trees, like Norway maple. Such trees as the Carolina poplar, which has a rapid growth, are a great temptation to the developer who is seeking immediate effect. There is no objection to them, provided they are planted alternately with the permanent trees, and also provided they are cut out before they encroach on the better tree. Great care is necessary that the trees be not planted too closely, as even after they are full grown there should be ample space between for light and air.

Norway maples should stand forty feet apart, giving each tree an opportunity for symmetrical growth, and that individual character so often lacking where trees are run together in the planting. The shadow effects are also much more pleasing where the sun's rays fall between the individuals in the row as well as between the rows of trees. Placing the trees in the position indicated, on the building line, will also give shade both to the sidewalk and to the front yards of the residents. Here, too, they are beyond the reach of horses standing at the curb.