Dogwood.—A native shrub of several varieties. Its low growing tendencies, its beautiful flowers and showy fruit make it a valuable ornamental shrub for parks. A species Cornus Florida grows into a tree some 25 feet high.
Douglas Spruce or Fir.—Snow[213] states this (Pseudotsuga) genus “is neither a true pine, spruce, nor fir, but a sort of bastard hemlock. The name ‘pseudotsuga’ is from pseudo, or false, and tsuga or hemlock.” These trees are among the largest known and the wonder of the traveler through the forests of Oregon and Washington. Along the lines of these roads it were well, if the pleasure of the tourist be of import, to retain the most beautiful specimens. It grows from 175 to sometimes 300 feet in height, and 3 to 5, and sometimes 10 feet in diameter.
Elm.—The American elm (Ulmus americana) is considered by many to be the best street and road tree in this country. It has a large rounded top with long graceful branches. The shade is not very dense and the lack of foliage near the ground allows the free circulation of air. It grows into an exceptionally fine individual specimen and will also group well. The general good appearance of the tree both in summer and in winter makes it a favorite. There are some fifteen different species of elm distributed over the temperate portions of the Northern Hemisphere, except along the western coast of North America. The wood being tough and fibrous it withstands damage from the wind fairly well. Occasionally the long branches become so heavy they break down, but usually the tree is so well balanced that it stands up well. The white or American elm is the favorite for road work. The red or slippery elm (U. pubescens) is a beautiful tree and would be used more frequently in road and park work were it not that its delectable mucilaginous inner-bark makes it the mark of the road vandal. White elm grows from 90 to 100 feet in height with a spread of 50 to 75 feet. There is a tree now being featured by the nurseries called English elm which has a smooth bark and very shapely appearance. The cork elm (U. racemosa), grows from 75 to 90 feet in height, best developed in southern Ontario and Michigan, with a somewhat rough shaggy bark, is also a good road tree.
Eucalyptus.—This genus includes about 400 species. They are variously and locally known as gum trees, stringy-barks, iron-barks, mahoganies, and box, and are natives of Australia and neighboring islands. They have been widely planted throughout the world in warm climates. The blue gum (Eucalyptus globulus) does well at least as far north as Sacramento, and has practically changed the landscape of Southern California and Arizona. The tree has an extremely rapid growth, reaching a height of 200 and sometimes 300 feet. Some of the trees have a shaggy exfoliating bark while others seem smooth. The leaves of the young tree in some of the species, very noticeable in the blue gum, change their form and color as the tree reaches a certain age. Likewise the color and shape of the leaves and flowers differ widely with different species. They all are “evergreen” but the leathery leaves are blue, gray, or green. The leaves of the blue gum are blue, oval, and stalkless when the tree is young while the leaves of the older trees have stems, are dark green, some 10 or 12 inches long, an inch wide, and sickle shaped. In southern California they have been known to grow 25 feet in one year. The various varieties may be used in various ways, some for wind breaks and massing and some for individual specimens. Some are brilliant with flowers during a period of year when other flowers are scarce. Eucalyptus oil extracted from them is used as a medicine. For dry warm climates they make an excellent road tree.
Fir.—There are a large number of species and like other evergreens have their uses in landscape work. They look much like the spruces. In the West many of them grow to tremendous sizes.
Gingko.—A picturesque tree, sometimes called the maiden-hair, has been used about the city of Washington for street purposes. Gingko biloba is a native of Japan. While beautiful it would require much care to get it properly started.
Gum Tree.—The name is applied to trees of diverse species. Sweet gum (Liquidambar styraciflua) grows from Connecticut to Florida, and westward, intermittently to Illinois and Texas. Greatest development in the basin of the Mississippi River. This is a tall, straight tree with symmetrical top, rather smooth bark with corky ridges. A good-looking road tree. The star-shaped leaves turn brilliant scarlet in the fall. The seed pods are a sort of bur or rounded ball. Black, or sour gum, while the wood is difficult to work and does not burn easily, ought to be a fairly successful road tree in some localities. Grows from 45 to 100 feet high.
Hedge.—See [Osage Orange].
Hackberry.—In the Western prairie states has proven itself to be a very good street tree. Grows to a height of about 50 feet with a spread of 30 feet. The bark is corky and deep cut, giving it a rough surface. In general appearance resembles the elm. Deserves more general planting.
Hemlock.—Is found native, in several species, over the northern part of the United States and southern Canada. Frequently found with broad-leaved and other needle-leaved timber. Tsuga canadensis grows from 60 to 80 feet in height, has short leaves, green above and light beneath, a straight trunk and beautiful appearance. Western hemlock is found as high as 6500 feet above sea level.