The pin oak takes its name from the fact that its branches are thickly set with short, pin-like twigs, many of which die but do not fall. These stubs stay on for several years. This fact alone will soon enable us to recognise the tree from a distance. No other species is so close-twigged, and the symmetrical form of this tree is very striking in the winter. It is a pyramid with many small branches thrust out horizontally from the main shaft. Below the middle of the tree, the long branches have a downward thrust, and the lowest ones often sweep the ground. Above the middle of the tree the branches are horizontal, and they gradually become shorter, and the tree ends in a pointed tip. There is no oak that I know which has so much the pyramidal form of evergreens like the firs, hemlocks, and spruces.
On the avenues of the city of Washington, we shall find superb double rows of American trees. On one which leads to the Navy Yard, I remember the beautiful pin oaks, uniform in size, perfect in symmetry, that stood in a double row along the sides of the avenue. To the crowds of tourists who visit the capital city every year, I hope that this will be an object lesson. In most towns and cities every owner plants the trees he likes in front of his house, so our streets and avenues present a mixture of trees of all ages, sizes, kinds, and conditions. The better way is for the city to plant the same tree in double lines, the whole length of a street, as has of late years been done in Washington. One needs only to see these trees coming on, each year adding beauty and dignity to the city, to realise that such planting may be done easily anywhere in the country, where trees as beautiful as the pin oaks grow wild.
THE WILLOW OAK
A Southern tree with slender twigs and narrow leaves like those of a willow, surprises us by bearing acorns! It is the willow oak, a beautiful, graceful tree for shade and for avenue planting. The tree naturally chooses wet ground, but it thrives where the soil is deep and well drained. I remember a fine large willow oak in John Bartram’s garden in Philadelphia, and a young tree in the Arnold Arboretum in Boston. This little one grows rapidly, but the frost nips its twigs in the winter. The species grows wild from New York southward, just back from the sea coast, to Texas. In swampy land, it is found from Missouri southward.
Willow oak acorns are downy, yellow-brown, and set in shallow saucer-shaped cups. The kernel is orange-yellow, and bitter. Half-grown acorns are found with the ripe ones on these trees, and the dark, rough bark agrees with others of the Black Oak Group. Though the leaves have rarely a side lobe, but are mostly narrow and plain-margined, the tip ends in a spine, as all black oak leaves should.
TREES WITH WINGED SEEDS
Why do the trees grow in such mixed groves, when Nature does the planting? Here and there we find solid groves of beech or oak, but the forest is, for the most part, a gathering together of all kinds of trees. A part of the beauty of any woodland is this variety in the planting. Under a tall oak we find a hornbeam, and under this the witch hazel, and under the witch hazel, a carpet of low woodland plants. We may walk in a straight line, or follow a woodland path a mile, and find every tree we meet is different from all the rest.
Many reasons explain the order in which Nature plants forests. One of the best of these is found in the kind of seeds trees bear. We shall find that trees most widely scattered are those whose seeds are winged. It is not hard to find, from May until far past midwinter, trees bearing light, winged seeds. All through the summer, the wind is busy sowing the seeds of the early-fruiting trees. In autumn, and all through the winter, the sowing of the larger crop goes on.
Let us begin our study with the maples, whose winged seeds every child knows. From the silver maple, whose seeds are dry before the first of June, there is a procession of ripening maple seeds that lasts throughout the year. A high wind shakes off the silver maple’s keys in showers in late May. Watch those in the tree-tops. The wind has a better chance up there. Each key, loosening from its twig, turns round and round in a dizzy whirl, and sails away still whirling as it falls, the heavy seed end always pointed downward. A tree is soon stripped, and the ground littered under it. But a great deal larger area than the tree’s shadow has the seeds scattered over it: the stronger the wind, the further these seeds go. Before the summer is over, a crop of little maple trees springs up from this sowing.
The red maple’s scarlet seed clusters turn brown, and the little winged seeds take flight in June. Lighter and smaller, they are carried longer distances than the seeds of the silver maple, and a crop of little red maples follows this June sowing of the trees.