IRLF B 3 flS3 TREES FOR TOWN AND CITY STREETS By F. L. Mulford FARMERS 1 BULLETIN 1E08 U.S.D.A FORESTRY ; LIBRARY Farmers' Bulletin 1208 United States Department oF Agriculture TREES IMP > LIBRARY , ONLY vigorous trees that will withstand the ad- verse conditions of a city should be planted on its streets. The habit of growth should be suited to the width of the street, and the foliage should be of a pleasing texture. Trees that bear showy flowers, fruits, or nuts are usually not desirable for street planting. Some trees are also objectionable because their roots penetrate defective sewers; others because they have a tend- ency to heave sidewalks. Oaks are probably more generally satisfactory for street planting than any other group of trees, fol- lowed closely by elms and sycamores. Palms do not make good shade trees, though some- times appropriate for formal effects. The silver and ash-leaved maples and the poplars are not often satisfactory. This bulletin describes the principal trees that are used for street planting in the United States. Contribution from the Bureau of Plant Industry WM. A. TAYLOR, Chief Washington, D. C. March, 1922 TREES FOR TOWN AND CITY STREETS. F. L. MULFOBD, Horticulturist, Office of Horticultural and Pomological Investigations. CONTENTS. Kinds of trees suitable for streets-- Qualities necessary Trees* for different regions Trees for special purposes Descriptions of street trees Acacia Ailanthus Ash Camphor Chinaberry Elm Eucalyptus Ginkgo Hackberry Honey locust 1 Page. 3 3 6 11 11 11 13 13 14 15 15 17 18 19 20 Descriptions of street trees Contd. Horse-chestnut * Linden Locust Magnolia Maple Oak Palm Pepper tree Poplar Rubber tree Silk oak Sweet gum Sycamore Tulip tree Page. 21 21 22 22 22 26 31 35 35 37 37 37 37 40 SUCCESS in tree planting on town and city streets depends upon three main factors proper conditions for growth, timely and intelligent care, and selection of proper varieties. The need of trees on city streets and their care are discussed in another bulletin; 1 in this are indicated the kinds of trees suited to different types of streets and to different regions. KINDS OF TREES SUITABLE FOR STREETS. QUALITIES NECESSARY. A tree must be adapted to the climate and to .the soil on which it is to be grown. For use under city conditions it must have healthy foliage that withstands dust and smoke and a root system not easily affected by unusual soil conditions, by restricted feeding areas, or by root pruning when street improvements are made. The top should be in proportion to the width of the street upon which it is used, and it should be rather high headed or easily trained to that form and of open growth. Of only a little less importance is the character of the foliage masses, whether dark or light, heavy and somber or open and airy, and also whether they have vivid autumn colorings. Only in the 1 See Farmers' Bulletin 1209, " Planting and Care of Street Trees." r< 1208. most southern parts of the country and in western California should evergreen trees be considered for street planting, and then only the broad-leaved evergreens, such as magnolias and live oaks. Where there is lack of sunshine in winter, due to short or cloudy days, it is desirable to admit all the light possible by using only deciduous trees. In all sections trees differ greatly in the time when they put out their leaves in the spring and lose them in the fall. Table I shows some of these differences in the coloring and the dropping of fall foliage. TABLE I. Comparison of the time when the leaves of various kinds of trees change color and drop in the fall, based upon observation* made at Wash- ington, D. C. (The number of years in which observations were made, upon which the percentages shown are based, is indicated by the figure in the small circle at the left of each percentage recorded.] Variety. Percentage of leaves dropped. Color of autumn foliage. Percentage of leaves colored other than green. Mid- October. Last, of October. Mid- October. Last of October. Red oak 1 68 2 50 70 5 90 10 72 86 53 18 13 7 35 85 40 45 14 64 60 44 100 85 31 77 53 10 80 Red and bronze 5 28 @ 50 5 30 75 100 Pin oak .. do . American elm Dead yellow English elm Yellow. Whiteash .do. 90 45 Bass wood.. . Brown edge Linden Yellow @ 30 5 100 50 20 88 50 21 850 40 Sycamore 115 2 2 65 20 8 8 43 13 80 23 15 60 Brown London plane. . . Ginkgo Yellow 90 Sweet gum Red.. Tulip tree Yellow 100 75 90 10 100 100 90 Horse-chestnut . . Brown edge Red maple Red.. Norway maple Yellow Sugar maple. Yellow and red Black maple do .. Silver maple.. . Yellow Box elder Eloney locust Black locust Yellow 8 10 Carolina poplar Lombardy poplar Sycamore maple Kentucky coffee tree Koelreutena SO 10 10 30 100 80 10 40 3 Swamp white oak Whiteoak Englishoak Narrow streets should be planted with tall slender trees (fig. 1) or sometimes with small trees. Broad streets may be planted with spreading trees (figs. 2, 7, 9, and 19), or, if provided with a central parking space, with moderate-sized trees in the center and on the sides, or with trees on the sides suited to the space and formal trees in the center. (Fig. 3.) As a rule, trees native to the locality that have been successfully grown in other cities should be given the preference. When a choice Trees for Todui' Witt Cttij must be made between untried native trees and those tested in a city or town under different soil or climatic conditions, it is better to give the native trees the first trial. Many promising native trees have not been planted on a sufficiently large scale or under sufficiently varied conditions to demonstrate their real value for street planting over any considerable area. Many of the trees mentioned in this bulletin may prove valuable far beyond the areas for which they are sug- gested. The bur oak, the swamp white oak, the scarlet oak, the chestnut oak, the white oak, the sour gum, and others may be found on further trial to be as valuable as those already demonstrated to be valuable over largo areas. Those men- tioned have all been tested in a small way. In many parts of the country trees with conspicuous flowers and those with edible fruits or nuts, and even horse-chestnuts, although the nuts are not edible, are badly mutilated by the pub- lic. Every effort should be made to cre- ate a sentiment that will protect these at- tractive additions to street adornment, but where the sentiment does not exist it is bet- ter to avoid the plant- ing of SUch trees ex- FIG. I. Narrow upright trees (Lombardy poplars) on a cept in a limited way. narrow street. Washington, D. C. ; midsummer. Some cities have ordinances against the planting of certain trees because their roots sometimes obstruct sewers. Among these trees are the Eucalyptus and some of the poplars. The silver maple is also bad in this respect. The roots of any tree are liable to find their way into a defective sew r er, but the trees mentioned are especially notice- able because of their vigorous root growth. It may be questioned whether a tree should be condemned for this growth, as it may be better to have a defective sewer thus revealed than to continue a menace to public health. The poplars and the silver maple are also objectionable because their shallow roots often interfere with pavements, especially poorly 1208. constructed ones. Besides the native trees many introduced trees have proved valuable. TREES FOR DIFFERENT REGIONS. To simplify the consideration of the kinds of street trees likely to prove satisfactory, the United States has been arbitrarily divided into the regions shown in figure 4, an endeavor being made to have each division represent an area with similar growing conditions. A discussion of the strong and weak points of the different kinds will be found with the descriptions of the kinds further on in this bulletin. FIG. 2. Live oaks, the handsomest southern street tree for broad streets. Biloxi, Miss. ; late summer. Region i. Region 1 comprises the mild humid portion of the northern Pacific coast east to the Cascade Mountains, including the western third of Washington and <>n-cron and a portion of northern California. The trees native to western Europe are adapted to this region, as the climatic conditions are quite com- parable. Most of our American trees also succeed here. Desirable varieties for street planting in region 1 are the Oregon, Norway, sycamore, and sugar maples ; California walnut ; tulip ; European linden ; bass- wood; sycamore; London plane; white and European ashes; English and American elms ; English, red, and pin oaks ; ginkgo ; and the black locust. Region 2. Region 2 is that portion of California lying between the Sacramento and San Joaquin Valleys and the Pacific Ocean. Many varieties of trees will succeed here if given water. Because of the lack of water, unless specially irrigated, the more drought-resistant species should be used. Deciduous trees useful for this region are the London plane; the California and common sycamore; English, Huntingdon, and American elms; Oregon, Trees for T'owh'dnd 'C FIG. 12. A street planted with honey locusts ; l:it . Washington, 1>. c the southern part of region 6, in region 8, and to some extent in regions 11 and 12. It thrives well under the same adverse moisture conditions as the common hackberry. The trunk and the large branches have little wartlike projections of the bark scattered irregu- larly over them. The small twigs are sometimes more or less spotted or winged in the same way. The tree is rather larger than the common hackberry and apparently is less subject to witches'-broom. HONEY LOCUST. The honey locust is a large, open, round-headed, fine-foliaged tree, admitting much light through its top. (Fig. 12.) The common form has .stiff spines 2 to 6 inches long, or even longer, but there is also a form without spines, which is the one that should be used for Trees for Town and City Streets. 21 street planting. It is a useful tree in regions 1, 2, 3, 9, 10, and 11, but is especially valuable for planting in regions 6, 7, and 8, and may prove useful in region 5. HORSE-CHESTNUT. The horse-chestnut has very showy blossoms, and when in bloom an avenue of these trees commands attention. It is, however, likely to be broken by boys clubbing it for its inedible nuts. It is a medium-sized round-headed tree that does much better under sub- urban conditions than in a city. It thrives in regions 1, 2, 3, and 10, but in some places its leaves are affected by a midsummer blight mm ii i \ ; *- FIG. 13. Basswoods in winter, Washinglon, D. C. which makes it unsightly during the remainder of the season. It is a close relative of the Ohio buckeye, which is also a handsome though less desirable tree. LINDEN. The basswood, or linden (fig. 13), is a large round-headed tree that is excellent for roadsides in surburban locations and does well on city streets if the conditions are not too severe. On account of the dark upper surface and the lighter under surface of the leaves and- the sweet-scented blossoms in early summer it is much admired. It is not as reliable as some of the other shade trees, as when young it is sometimes attacked at the base of the trunk by a fungous growth that kills the tree. When once established, it forms handsome avenues. It is suited to regions 1, 2, 3, 4, 7, 9, 10, and 11. 63943 22 Bull. 1208 4 22 Farmers' Bulletin 1208. The linden, or European linden, has much smaller leaves than the American linden or basswood, with more contrast between their tipper and lower surfaces. It is about the same size, but is a little more compact in growth and holds its leaves longer in the fall. It is a useful tree for street planting in regions 1, 2, 3, 4, 9, 10, and 11. LOCUST. The locust, or black locust, is a desirable street tree in regions 6, 7, and S, and probably in region 5, as it thrives with comparatively little moisture. It makes a moderate-sized oval head that bears sweet- scented white flowers in late spring or early summer. Its greatest drawback is its liability to serious injury and disfigurement by the locust borer, 4 but with proper care this injury can be prevented. 5 In some parts of the East it is also subject to a leaf miner that gives its foliage a burned appearance. In region 3 it holds its seed pods for several years, and thus becomes very unsightly. MAGNOLIA. The evergreen magnolia is one of the few good evergreen trees (fig. 14) for street planting, but it is adapted only to regions 1, 2, 3, 11, 12, and 13. There are but few conditions that warrant the plant- ing of a tree having foliage as thick as this because of the dense shade, which is especially undesirable in winter. It grows to be a large oval-headed tree and bears beautiful large white blossoms in late spring or early summer. MAPLE. Among the maples are some undesirable trees much used for street planting and some that are valuable only in restricted areas or under special conditions. The maples are not as satisfactory for street planting as usually has been supposed, few of the species being suit- able for this purpose and these only in a limited way. The ash-leaved maple, or box elder, is native to all of the country east of the Rocky Mountains except the regions near the South Atlantic and Gulf coasts. It is a small, quick-growing tree that will thrive almost anywhere, but it reaches maturity early. There m:i\ be conditions requiring the use of this tree in regions 6, 7, and 8, but because of its early decay and of its being subject to destruction by wind it should be grown only when the other trees suggested for these regions will not succeed. The English maple is small, round headed, with small dark-green leaves, useful in regions 1, 2, 3, and 4. * Cylene roltiniae Forst. 6 Soc I". S. Dept. of Agriculture r.ullctin 7X7, entitled " J'rotertion from UK* Locust Borer." dorsalis Thunb. Trees for Town and City Streets. 23 The Norway maple is round headed and eventually reaches large size, but, as compared with most of the other maples, it is slow grow- ing (fig. 11, C). The persistence of its tendency to form a low head makes it difficult to give it a high head of desirable shape (fig. 15). FIG. 14. Magnolia, or evergreen magnolia. A good street tree where an evergreen is permissible. It is also very thickly branched, and its foliage, being heavy and dark green, permits little light to pass through. On this account it is rather undesirable for street planting. By severe pruning of the interior of the head this defect may be somewhat overcome. The tree is practically free from disease and insects, with the exception of 24 Farmers' Bulletin 1208. a leaf aphis, 7 which produces yellow spots on the leaves and causes them to drop prematurely; also, the honey dew which they produce is so abundant at times as to cover the leaves and wet the sidewalk beneath the tree, the leaves under certain weather conditions becom- ing blackened with dust accumulating and a fungus growing in the secretion, thereby giving the tree an unsightly appearance. This aphis, however. i.s not always present and does not seriously injure the tree. The Xorway maple comes into leaf later than most of the other maples, but holds its leaves later in the fall. They usually assume a bright yellow hue be- fore they drop. The leaves are preceded by an abundance of yel- low - green blossoms. On account of its dense shade and masses of fine fibrous roots it is difficult to grow grass under this tree. Its good shape and attractive dark- green foliage make it popular for street planting in spite of its dense, low head. It will succeed in re- gions 1, 2, 3, 4, 9, 10, 11, and 12. The Oregon maple, also known on the its poor Pacific coast as broad- leaved maple, is the large-leaved maple of the northern Pacific slope. It forms a large round head, and with its unusually large dark-green leaves makes a very attractive street tree that succeeds well in regions 1, 2, 3, and 4. It is valuable and worthy of more extended cultivation on the Pacific coast. The red maple, scarlet maple, or swamp maple is one of the most widety distributed American trees. It is found from Canada to the Gulf of Mexico and west to the Rocky Mountains. Its leaves are the smallest of the eastern native maples, but it grows large and FIG. 15. A Norway maple In lato wintor, showin shape when trimmed to a high head. Trees /or Town and City Streets. is usually of rather upright outline. It is better adapted to suburban conditions than to city streets and is one of the few trees that suc- ceed well near the ocean. It has bright-red blossoms before the leaves appear. The young leaves and fruits are also red. The mature leaves begin to color early, some branches coloring as early as the middle of July, assuming brilliant reds and yellows and stay- ing on later than those of the sugar maple. It is a handsome tree that is not as much used as it deserves to be in regions 1, 9, 10,' 11, 12, and 13. The silver maple, also called the soft maple, white maple, and swamp maple, is probably more used for street planting through the whole United States than any other tree, though it is one of the least desirable. It is usually planted be- cause it is a quick- growing tree, but it is not more rapid in growth than several other trees that are much better. There are three serious ob- jections to its use as a street tree. The first is its brittle wood, which at an early age is easily broken by ordinary windstorms and causes it when a comparatively young tree to become unsightly. The second is its shallow rooting, which has a tendency to destroy pavements and also makes it difficult to grow grass near the trees. The roots also will grow into sewers. The third is its tendency to decay; the tips of the limbs frequently die, leaving the whole top of the tree bare of leaves, and the wood decays quickly, especially if the bark is broken. For this reason it does not stand pruning as well as most other street tre'es, and it probably has been pruned more ruthlessly than any other, unless it is the Carolina poplar. It should never be severely deheaded or, as it is popularly called, " dehorned" (fig. 16), FIG. 16. Silver maples severely headed back, an improper way to treat trees, especially silver maples, except under very unusual conditions. Washington. D. C. ; midsummer. 26 Farmers' Bulletin 120$. as the stubs will practically never heal over, and from these cuts decay will start, which in a very few years will rot the center of the limbs and trunk and thus destroy the tree. Although it forms a large round head with an open top and its foliage is pale green above and almost white beneath, making a very delightful shade, it should not be used for street planting where other trees can be made to grow. Its use may be warranted, h o w - ever, in region 7. The sugar maple, or hard maple (fig. 17), is especially adapted to gravelly soils in re- gions 1, 10, and 11, the northern parts of re- gions 2 and 3, and the eastern and southern parts of region 9. It is oval headed, large, and handsome. The leaves come early, but in late summer they begin to turn brilliant yellow and red and drop before most other leaves. The sugar maple does not thrive under city conditions, but it is admirably adapted to suburban streets. Although the sycamore maple is similar in appearance to the Norway maple, it is not a satisfactory street tree in the eastern United States. It succeeds, however, in regions 1, 2, 3, and 4. OAK. Of the trees used for street planting the oaks are best. They probably have not been more widely planted because of the preva- lent belief that they are slow growers and because in the North they are rather difficult to transplant. Although some of the handsomest species, like the white oak and live oak, are slow growers, those suitable for street planting are comparatively rapid growing. The white oak and sugar maple shown in figure 17 are each 32 years old and although differing in shape are practically the same size, yet the sugar maple has been considered a sufficiently rapid growing tree to be planted frequently as a street tree, while the white oak has 4-4 FIG. 17. A sugar maple (on the loft) and a white oak (on the right), each 32 years old and nearly the same siza Trees for Town and City Streets. 27 seldom been so used, probably because of an erroneous impression that it is of too slow growth. The oaks are hardy, most of them are long lived, and for the most part they are free from disease and insect attacks. Some of the southern species are subject to attacks of mistletoe. The California live oak is an evergreen suitable for use in region 2 and succeeds adjacent to the ocean. It is also useful in region 3 and in the western part of region 5. It is easily transplanted when young, especially when planted from pots. FIG. 18. A Darlington oak in winter, Darlington, S. C. The chestnut oak is a native of gravelly soils on eastern moun- tains and is suitable for similar soils in suburban locations in regions 9, 10, and 11. It is a large, handsome tree. The Darlington oak (fig. 18) is a form of laurel oak especially desirable for street planting. It is large, round headed; the leaves are a trifle narrower and not quite so nearly evergreen as the laurel oak. It is found wild about Darlington, S. C., where a good form of the laurel oak appears to have been introduced as a shade tree in the early part of the nineteenth century. Its range of usefulness lies in regions 11 and 12. The laurel oak is a large oval-headed tree that is not as rugged and irregular as the live oak, but is suitable for street planting in 28 Farmers' Bulletin 1208. regions 11, 12, and 13. It has large, thick, glossy leaves, and in the warmer regions it is almost evergreen. It is readily trans- planted, but as it is not so common in the woods as the willow oak and the water oak it has not been so much used as a street tree. The live oak (fig. 2) is probably the noblest and most majestic of the oaks of regions 12 and 13. It is evergreen and of slow growth, but wherever it is found, whether on streets or in public parks, it is the pride of the people. Although an evergreen, it is sufficiently open headed to make a good street tree. When it becomes old it is spreading, and as a rule does not form as high a head as the willow oak and the laurel oak. Compared with other southern oaks it is difficult to transplant. It is of sufficient merit to be used on broad streets, and especially on boulevards, where the good of the future as well as the present is considered. The mossy-cup oak or bur oak is native in the northeastern part of the United States and west of the Mississippi River on the hills lying between the river bottoms and the prairies west to the western parts of the Dakotas and Nebraska and central Kansas and Texas. It is a large, handsome tree that should prove satisfactory under suburban conditions in regions 7, 8, 9, 10, and 11 and on fertile well-watered soils. The pin oak (fig. 11, A), sometimes called the swamp oak, is a tall tree, conical when youn it is desirable that a good strong leader should be developed, so that the lower limbs may be removed from time to time as conditions require. The pin oak thrives on wet and on heavy clay soils, as well as on a wide range of other soils. Figure 11 shows pin oaks, Norway maples, and ginkgos 18 years old on adjacent streets, and illustrates the rapid growth of this oak. At the time of planting these trees the pin oaks were thought to have the poorest location. This tree is adapted to regions 1, 2, 3, 4, 9, 10. and 11. The red oak (fig. 19) is probably the best tree for street planting in regions 1, 9, 10, and 11 and is satisfactory in regions 6, 7, 8, and 12. It is a large, oval, open-headed tree of rapid growth. Under good conditions a young red oak will grow 4 feet in a single season. Like the other oaks it is slow in coming into leaf in the spring, but holds its foliage late in the fall. The leaves usually turn a brilliant red before they drop. It is comparatively free from insect and fungous attacks, and it is one of the few trees really suitable for planting close Trees for Towii'diid"Glfij Streets.'"' 1 29 to the ocean, as it thrives on sandy lands only a few feet above high tide or within the reach of ocean spray. The scarlet oak is a large, open,, round-headed tree. Its leaves are more deeply divided than those of the red oak. The leaves turn a brilliant scarlet in autumn, being even more gorgeous than those of the red oak. This tree is adapted for street planting and is especially desirable for suburban conditions in regions 1, 9, and 10. The swamp Spanish oak is adapted to regions 11, 12, and 13. It belongs to the red-oak group, but is larger than the other oaks sug- gested for street planting. It is well adapted to suburban locations, but apparently it has not been tested under severe city conditions. FIG. 19. A street shaded with red oaks in midsummer, Washington, D. C. The valley oak is a beautiful tree for regions 2 and 3 and the more favorable parts of region 5. When transplanted young, especially if taken from a pot, it is easily established where there is opportunity to water it for a few years. The water oak is frequently confused with the willow oak and the laurel oak, as these three oaks are not distinguished from one another except by close observers of trees. It is probably more used than any other tree in the cities of region 12 and the adjoining por- tions of region 11. It is the weed of the southern oaks and one of the weeds of the street trees of the Southern States. It is comparatively short lived and seems to be more subject to attacks of mistletoe and more easily affected by windstorms than the willow oak, the Darling- ton oak, and the laurel oak. This tree should not be planted, because it is less desirable than the other oaks mentioned. The willow oak (see fig. 5), sometimes erroneously called the water oak, is one of the best of the quick-growing oaks for use in regions , * * \ 30 "''Tattle ft*' 'Bulletin 1208. FIG. 20. Leaves of some of the southern oaks : A, Live oak ; B, willow oak ; (7, laurel oak and D, water oak. Trees for Town and'^City' Afreets." 31 11 and 12. It is frequently used with the water oak for street plant- ing and is usually confused with it. It is, however, a distinct tree, which can be distinguished readily from the water oak. It is longer lived and is its equal in every other respect. Trees of this variety which apparently have been planted about 80 years are found in excellent condition, while water oaks planted at the same time have either entirely disappeared or are showing marked evi- dences of decline. Figure 20 shows the characteristic appearance of the leaves of these nearly related species of oaks. In the South the willow oak is readily transplanted, as trees 12 feet high are dug from the woods and planted on the street with success (fig. 21). FIG. 21. Willow oaks, transplanted from the woods, as they appeared near the eud of the second summer. Montgomery, Ala. In the extreme South this tree is nearly half evergreen. Its foliage does not assume the bright colors of the trees of the red-oak class. PALM. 8 Several varieties of palms are used more or less for street planting in regions 2, 3, 5, 12, and 13. Though sometimes effective as a formal street decoration (fig. 22), they can hardly be considered shade trees. PALMETTO. Palmettos, or sabals, abound in region 12 near the coast ; succeed in regions 3, 5, and 13; live in region 2; but are seldom grown satis- 8 The palms are treated on the basis of notes furnished by Dr. O, F. Cook, of the Bureau of Plant Industry. 32 1208. factorily close to the Pacific coast. They can be used effectively for formal plantings along some streets, park drives, or in liberal central parking spaces in boulevards, but they are not useful as a substitute for shade trees. Their leaves and damaged roots should be cut off in transplanting, and they should be set about 3 feet deep in their new location. The Carolina palmetto is a native of and useful in regions 12 and 13, where it sometimes attains a height of 60 or 80 feet. It will thrive in regions 3 and 5, but is used less there. The Texas palmetto is especially valuable for southern Texas, where it is indigenous, and it is likely to succeed generally in regions FIG. 22. A formal planting on a city street. Palms with interplantings. Calif., in midsummer. Redlands, 3, 5, and 12. It grows to a height of 40 feet and in appearance is quite distinct from the Carolina palmetto, the leaf segments being much broader and less drooping. The Victoria palmetto 9 is another hardy species, probably a native of Mexico, but grown for many years at Victoria, Tex. It is similar to the native Texas species and worthy of general planting in the same region. A feature of this species is that the persistent leaf bases remain alive and green for many years instead of turning yellow or brown, as in the Carolina palmetto. WASHINGTONIA PALM. Washingtonia palms are a very conspicuous feature of street and ornamental planting in southern California. Two species are rep re- v Cook, O. F. A new ornamental palmetto in southern Texas. In U. S. Dept, Agr., Bur. Plant Indus. Cir. 113, p. 11-14. 1913. Trees for Town and City Streets. 33 sented, Washingtonia filifera Wendland and W. robusta Wendland. The first is a native of the canyons and barren slopes that surround the Coachella Valley of southern California, while the other species probably was brought in the early days of travel by way of the Isthmus of Panama from the region of San Jose del Cabo, the ex- tremity of Lower California. The name robusta is used because this species grows much more rapidly in height than W. filifera, though the trunk is more slender. Both species are hardy and thrive well through regions 2, 3, and 5, and also in regions 12 and 13. Washing tonics robusta requires less heat than W. filifera, but both will endure several degrees of frost. Even in California Washing- tonia robusta is distinctly preferable for localities near the coast. In the vicinity of San Diego the leaves of Washingtonia filifera be- come badly infested with a parasitic fungus that does not attack Washingtonia robusta. OTHER HARDY FAN PALMS. The species most commonly used for street and ornamental plant- ing in the California coast districts is the Chinese or windmill palm. This palm has a slender trunk clothed with brown fibers, flat fan- shaped leaves, and rather straight radiating segments. The same species is hardy at New Orleans and Charleston, and even at Laurens, S. C., at an altitude of 600 feet, but it does not thrive in the sandy soil of Florida. The vegetable-hair palm, a native of Spain, Sicily, and North Africa, is similar to the Chinese palm but smaller and more compact and with large, sharp spines on the petioles of the leaves. When young it suckers from the base, like the date palm, so that clusters of it may be formed. The Guadalupe Island palm is one of the most popular species in southern California in the region of Santa Barbara, Los Angeles, and San Diego. This palm is a nafive of Guadalupe Island, off the coast of Lower California, and is not known to occur elsewhere in the wild state. It is well adapted to the cool coast climate of Cali- fornia, but not to the interior valleys. It is smaller than the Wash- ingtonia palms, with a rather short trunk, 15 to 20 feet high, and a dense crown of fresh green leaves. The California blue palm, formerly placed in the same genus with the Guadalupe Island species, is very distinct in habits as well as in general appearance, having bluish or grayish green leaves, strongly toothed petioles, and long, slender flower clusters. The trunk is very robust, often 2 to 3 feet in diameter, and attains a height of 30 to 40 feet. Several of these features are shared with the Washing- tonia palms. It also has the ability to grow in the dry, hot interior 34 *''; --'. yFarfntFs :BtiUetin 120$. valleys (regions 3 and 5). In Texas the blue palm has proved hardy at San Antonio, and even as far north as Austin. DATE PALM. The Canary Island date palm is the most popular palm for park or street planting, being more hardy than the true date palm, larger and more vigorous in growth, and producing no suckers from the base of the trunk. Well-grown specimens in the California coast districts (region 2) with trunks from 2 to 3 feet thick and immense crowns of spreading deep-green leaves are among the most imposing forms of plant life. The leaflets instead of radiating from one point, as in fan palms, are arranged along both sides of a common stem or midrib. Palms with this arrangement of leaves are called pinnate palms. Though less robust in other regions, the species is very hardy and adapted for planting anywhere in the palm belt (regions 3,5, 12, and 13). The true date palm is adapted to the warmer parts of regions 3 and 5, but it is much inferior to the Canary Island species for orna- mental use because the foliage is less attractive, owing to its habit of sending out suckers from the base of the trunk. THE COCONUT AND ITS RELATIVES. The true coconut palm is confined to a narrow belt along the coast of southern Florida, but other species of Cocos are planted in the coast districts of California. The species that is most prominent in park and street plantings around San Diego, Los Angeles, and Santa Barbara is usually known as Cocos plumosa or Cocos romanzofficfria, and is a rather tall, slender palm with a long- jointed trunk about 1 foot in diameter and long, spreading, feathery, deep- green leaves. Another series is represented by Cocos yatay and several similar species, often called Cocos austmlis in nursery cata- logues. They have short, thick trunks, grayish or bluish foliage, and fleshy edible fruits, highly flavored, somewhat like pine- apples. These- gray-leaved species are very hardy. Another coco- nut relative is the Chilean molasses palm, which has a massive trunk 3 or 4 feet in diameter, specimens of which are growing at a few places in California. OTHER PINNATE PALMS. The amethyst palm, a native of Australia, is commonly planted in California. It usually appears in lists and nursery catalogues as Seaforthia elegans or Archontophoenix alexandrae, but it is now recognized as distinct from both of these species and has received a new name, Loroma ametkystina. Except certain species of Phoenix and Cocos, it is the only pinnate-leaved palm that grows freely in Trees for Town and City Streets. 35 the open air in the coast districts of California, from Santa Barbara to San Diego. In habit and general appearance Loroma is more like the royal palm, though with a smaller trunk and fewer leaves. The pinkish purple drooping flower cluster is very attractive and develops into a large cluster of scarlet berries. The royal palms, species of Roystonea, are perhaps the most striking ornamental members of the whole group. They can be grown in southern Florida and even exist in the wild state in some of the hammocks below Miami. PIG. 23. California pepper trees, Riverside, Calif. PEPPER TREE. The California pepper tree (fig. 23) is much used in regions 2 and 3 and in the western part of region 5. It is a moderate-sized, broad- headed tree with fine foliage, which gives it a light, airy appearance. During the fall and winter it is covered with scarlet berries, which in contrast with the persistent foliage produce a pleasing effect. POPLAR. Poplars are not desirable for street planting. Their wood is easily broken by ordinary windstorms, and their roots run near the surface and are likely to interfere with pavements, as shown in figure 24, while those of some varieties are especially likely to make 36 Farmers' Bulletin i208. trouble in sewers by filling them with a mass of fibrous roots if access is once gained. Vigorous root growth is encouraged by the moisture from a leak, and the roots ultimately find their way inside. The mature seed is carried by a cottonlike appendage, and in many varieties this is so abundant as to be another serious objection to the planting of these trees. The southern cottonwood, Carolina poplar, and the northern cot- tonwood are very similar in their adaptability for street-planting purposes. They are easily propagated, easily transplanted, are quick growing, and where they reach maturity under normal conditions form very large oval-headed handsome trees, but under the artificial conditions existing in cities it is necessary to prime them quite se- FIG. 24. A pavement heaved by the roots of poplar trees. verely when young to remove the long vigorous growths and make the heads more compact. This pruning stimulates more vigorous growth, which must be removed or they will form long branches with heavy tops that are especially liable to injury by windstorms. The more they are pruned the greater the tendency to an undesirable form of growth. They begin dropping their leaves early in the summer and lose them very early in the autumn. Their root growth is vigorous, especially in the presence of abundant moisture. Ex- cept in regions 6, 7, or 8, or in locations where smoke and fumes in the air prevent the growing of other trees, they should not be planted. The Lombardy poplar is a tall columnar tree adapted for use on very narrow streets. (See fig. 1.) It is short lived in many places, Trees for Town and City Streets. 37 owing largely to the European poplar canker, but otherwise is a satisfactory tree for these conditions in all parts of the United States. The trees may be planted as close together as 30 feet. None of the other poplars have much to recommend them for street planting. RUBBER TREE. The rubber tree is a large-headed handsome evergreen, suitable for regions 3 and 5 and the southern parts of regions 2 and 13 when the use of an evergreen tree is warranted. SILK OAK. The silk oak, or Australian fern, is a large, handsome tree that succeeds well in regions 2, 3, and 13; also in region 5 if provided with a reasonable amount of moisture, as it stands drought remark- ably well. It is covered in early summer with orange-colored flowers. SWEET GUM. The sweet gum (fig. 25) is adapted to regions 11, 12, and 13, especially on sandy lands. It forms an oval-headed, handsome tree with star-shaped leaves that assume a particularly brilliant hue in the autumn. It is better adapted to suburban conditions than to the heart of a city.' Toward the northern limits of its successful cultiva- tion it is difficult to transplant, while in the warmer sections of the country it can be moved with comparative ease. It should be trans- planted only in the spring. SYCAMORE. The sycamore, also called the buttonwood and buttonball tree, is a large, open, spreading, quick-growing tree native along water- courses. It is adapted to regions 1, 2, 3, 4, 9, 10, 11, 12, and 13 and is worth testing in regions 5, 6, 7, and 8. Its habit of shedding its outer bark in large flakes, leaving the white new bark showing in large patches, makes it a conspicuous tree wherever grown. The fruits are balls 1 inch or more in diameter and are sometimes ob- jected to because they make dirt when falling; also the shed bark is considered objectionable. It is such a strong-growing, handsome tree and succeeds so well under city conditions that it is being planted more and more frequently. It will stand more pruning and shaping than any other street tree. Without pruning it is too large for ordi- nary streets unless spaced at almost double the usual planting dis- tance, with the trees staggered along the street instead of being planted opposite. Its high head and open habit of growth are dis- tinct advantages for street planting. Its foliage, too, is a light green ?j 38 Farmers' Bulletin 1208. FIG. 25. Sweet-gum trees, Washington, D. C. Trees for Town and Citi/ Streets. 39 which gives an impression of airiness with the shade. It is subject to attack by a fungus that kills the leaves while still small or par- tially mutilates them, giving them an unsightly appearance. In some places this trouble is rather serious. The California sycamore is a native of California, adapted to regions 1, 2, 3, and 4, and portions of region 5. It is similar in gen- eral characteristics to the sycamore. FIG. 26. London plane trees, Washington, D. C. The London plane tree is one of the Old World forms of sycamore (fig. 26). According to Alfred Render, 10 "the true oriental plane is rare in cultivation, the tree usually planted under this name being Platanus acerifolia" It is more compact in habit of growth and has the other good qualities of the sycamore. It is being more and more used on city streets and is proving satisfactory in regions 1, 2, 3, 4, 9, 10, 11, and 12. It will probably succeed in the warmer parts of regions 6 and 7 and also in regions 5 and 8. It is a more desirable tree for ordinary use than the sycamore, on account of its more compact habit and comparative freedom from disease, though it is tender in the northernmost sections. 10 Bailey, L. H., ed, New York, 1916. Standard Cyclopedia of Horticulture, v. 5, p. 2707. 40 Farmers' Bulletin 1208. TULIP TREE. The tulip tree is also sometimes called the tulip poplar (fig. 27) or yellow poplar, though the latter names are unfortunate, as the tree is not a poplar or even closely related to the poplars. It is a large, rapid-growing tree suitable for suburban conditions in regions 1, 2, 10, 11, and 12. The leaves are of unusual form, the upper half ap- pearing to have been cut away, leaving a notch about where it would FIG. 27. Tulip tn-os, .some! inn H), D. C. seem the middle of the leaf should be. The color is a light green. The roots are unusually soft and tender, and therefore the tree needs to be transplanted quickly and with great care. Small sizes should be planted, especially near the northern limits of growth. It should be transplanted only in the spring. If after transplating it the top should die and a new vigorous shoot should put out from the root, it would be desirable to form a new top from this shoot rather than to transplant another tree. HOW TO DO IT. DO YOU WANT practical suggestions on how to build a silo, a hog house, a poul- try house, a potato storage house, or how to make a fireless cooker, or other farm home convenience, a fly trap, or a self-feeder for hogs? Are you seeking ideas on how to pre- pare vegetables for the table, how to care for food in the home, how to bake bread and cake, and prepare appetizing foods in an efficient and economical manner? Is there some prac- tical question about your corn or wheat or cotton or other crops, or about your poultry or live-stock, to which you are seeking an an- swer? The answers to thousands of such questions and practical suggestions for doing thousands of things about the farm and home are contained in over 500 Farmers' Bulletins, which can be obtained upon application to the Division of Publications, United States Department of Agriculture, Washington, D. C. WASHINGTON : GOVERNMENT PRINTING OFFICB : 1923 Gaylord Bros. Makers Syracuse, N. V PAT. JAN. 21 ,1908 ERKELEY LIBRARIES TO FORESTRY LIBRARY 260 Mulford Hall LOAN PERIOD 1 QUARTER 2 3 4 5 6 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS