Some trees branch low, and their short trunks break into great limbs whose ample spread forms a dome much broader than its height. The white oak in the North and its evergreen counterpart, the live oak of the South, illustrate this noble form. Somewhat like them, but with its dome elevated upon a tall trunk, is the American elm with the fan top. The lines of the elm branches are all curves from the arching limbs that rise out of the trunk to the flexible twigs which droop at the extremities of the branches. The dome of a white oak is made of angular limbs. Even the twigs are likely to be crooked. No one would confuse the elm with an oak.
Round-headed trees are many. Go from the apple tree in the orchard to the red and Norway maples along our streets. A great many trees find this form best adapted to spreading their leaves out towards the sun. Many oaks and ash trees, the hickories and birches, and the beeches have widely spreading limbs forming tops that are oblong in shape. There are trees so irregular in habits of growth that we shall never know them by their forms alone.
The winter is the best time to study tree shapes, for then the framework is revealed. The trees to study are those which stand apart from others, so that they have been able to take their natural shapes. These we shall find growing on the streets, and in yards, and parks, and in open spaces in the woods. Where trees crowd each other in growing, their branches chafe and clash in storms, destroying the buds and leaves, and bruising the tender bark. Such limbs die of these injuries, and the whole shape of the tree top is changed by its losses.
Fruiting branch of the cockspur thorn
Left: Clustered thorns on trunk of honey locust tree.
Right: Flowers and foliage of the black locust
It is hopeless for lower limbs to live in a dense pine forest. The top branches form so thick a wall of shade that lower branches die from lack of sun. It is the same with broad-leaved trees. In any dense woods, the trees stand bare as telegraph poles, lifting small heads of foliage at the top, and competing there with their neighbour trees for sun and air. It is only when set apart from other trees that a trunk can keep its lower branches hale and strong as those at the top.
The weeping habit gives us some strange tree forms. The Camperdown elm forms a shady summer-house on many a lawn by arching limbs which droop to the ground on all sides of the main trunk. The weeping mulberry has the same habit. Weeping birches and willows have such light foliage, and such fine, flexible twigs, that they look like fountains of green as they stand among the other trees.
All weeping trees are made by grafting in the nursery rows. They are not grown from seeds, and it is not true that they “weep” because of being planted up-side-down! This preposterous notion is not uncommon.