Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. HANDBOOK O FvN A T I V E WOODY PLANTS OF_THE UNITED STATES by William R. Van Dersal Biologist t Section of Wildlife Management PREPARED FOR THE TECHNICIANS OF THE SOIL CONSERVATION SERVICE SCS-TP-11 July, 1936 United States Department of Agriculture National Agricultural Library Advancing Access to Global Information for Agriculture • FOB^ORD If the excellence of two and a half years of operation 1 a3 done anything for us as a Service, it has proven .now absolutely right our leader, Dr. Bennett, has been in his insistence upon a program wherein all practicable measures for the control of erosion are closely co- ordinated into a single land-use plan worked out on the particular farm on which it is to be applied. In the execution of this program it is but natural that we should have gained a clearer understanding of one of its cardinal principles, the maximum possible restoration of the vegetative cover of the soil. Some of our early projects were conducted seemingly on the assumption that this principle applied only to crop and forage plants, though most of them soon conceded a place in the urogram to certain trees, ^ow the project without its forester is rare, and woodland management has long since taken its rightful place in our operations More recently a Section of Wildlife Management has been added to our operating units, but is already active in planting large numbers of shrubs. Because this great group of plants of high erosion control potentialities heretofore has been almost wholly neglected, the new Section is certain to become increasingly important as additional biologists are found to carry on its work. All of these men, biologists and foresters alike, are being called upon to prepare planting lists of a wide variety of woody stock, yet even before the first spadeful of sod was scalped from the steep Wisconsin hillsides of old Project No. 1 the need was keenly felt for a reliable source to which the harassed technician might turn for information con- cerning the characteristics of the plants he would use. No such source existed short of a complete botanical library, which, of course, was not available to any field office. Thus was born a tendency to rely too much on a limited number of well-known species which we recognize as being a temporary situation to be corrected .as soon as possible. I feel, therefore, that while Dr. Van Dersal has kept the needs of his own section uppermost in mind during the preparation of this Handbook, he has performed a distinct service for our organization as a whole by bringing together for the first time the existing information pertinent to our needs in using woody plants. I commend his work to the careful study of all technicians having occasion to employ such vegetation, and earnestly hope that it will stimulate a more varied and bettor balanced planting program throughout the Service. C. 3. Manifold, Chief Division of Conservation Operations .258 1 ACKNOWLEDGMENTS At the suggestion of Mr. Ernest G.« Holt, Head of the Section of Wild- life Management, Soil Conservation Service, and advised and encouraged by him, the author undertook the compilation of this list. The stimulating cor- respondence during 1935 > his relentless and constructive criticism in 193&, and his always thoughtful efforts to ensure that the author did not get side- tracked in his zeal to work out the problems have, more than anything else, made this work possible. In the preparation of the list a great deal of data has been found in the various publications and mimeographed pamphlets written by Mr. W. L. McAtee, of the Biological Survey. His work is so well known and authorita- tive in the field of bird foods as to make any adequate treatment of the subject impossible without frequent reference to his material, while his stimulating conversations have aided a great deal in this undertaking. "Important Western Browse Plants", by William A. Dayton, of the U. S. „-* Forest Service, has supplied very valuable information pertinent to characters and forage values of southwestern woody species. It is much to be regretted that this admirable publication is no longer in print. Valuable suggestions and ideas with respect to the use of woody species for erosion control, have been offered by Professor M. L, Fernald, of Harvard University, Mr. Alfred Render, Mr. E. J. Palmer, and Dr. Hugh M. Raup, of the Arnold Arboretum; and by Dr. H. A, Gleason, Dr. W, H. Camp, specialist on the Ericaceae, and Mr, E. J. Alexander, collaborator with Dr. J. K. Small, of the New York Boto.nical Garden. Discussions with Mr. A, C. Molntyro, Regional Forester, of the Soil Conservation Service, proved also of much help. Mr. E. P. Killup, of the U. S. National Herbarium, has been ready always to assist in the botanical work. To all of these men the author wishes to express his thanks. 2. It is with the utmost appreciation of the courtesy and help given "willingly at every opportunity by the Biological Survey, that the author acknowledges the particular efforts of Mr. Clarence Cottam, Head of the Section of Food-Habits, and his assistants Miss Evelyn Knappen, Mr. F. M. Uhlor , and Mr. Neil Hotchkiss. The contribution of the nap of plant growth regions by Mr. F. L. Mulford, of the Bureau of Plant Industry, is gratefully acknowledged. As reproduced here, many changes and alterations in the boundary lines appear for the first time. Without any doubt, the great importance of Mr. Mulford 's work will .be increasingly recognized not only by agriculturalists, horti- culturalists, and landscape gardeners, but by botanists as well. The author, therefore, feels very keenly the kindness of Mr. Mulford in permitting the use of his revised map in this publication. William R. Van Dorsal Washington, D. C., May, 1936 3 INTRODUCTION As every soil conservationist knows, there is a very definite rela- tion between the density of the plant cover on the soil, the amount of soil lost through erosion, and the productivity of that soil. These three func- tions vary with each other in a regular and direct manner, and there is no reason to believe that they have not always done so. Soil is partly formed by vegetation, and vegetation is in good part a product of the soil. Taking the hint from our observation of natural conditions, we must expect to direct our efforts at erosion control toward revegetation, since it is known that erosion starts with the destruction of the plant cover, and that the kind and density of vegetation is more important in influencing run-off and erosion than is steepness of slope or intensity of rainfall. * For our purposes there are two kinds of vegetation which we may util- izc-permancnt and temporary. Under our present agricultural system we are concerned with the proper manipulation of cultivated crops in such a manner as to keep the maximum of cover on the soil as much of the time as we can. Such manipulated cultivable crops fall into the temporary class of vegetation. The p ermanent class includes plants which arc permitted to remain on the ground without disturbance except to gather from them such periodic crops as they may produce. It is the purpose of this paper to consider in partic- ular the woody species, which can be utilized to aid in controlling erosion, and to examine some of the qualifications justifying their use in a planting program. Coincidental with the comparatively sudden demand by the Soil Conservation Service for millions of shrubs and trees to plant for erosion control, there has arisen an equally great demand for information about the *Data from U. S. Forest Service, Intermontane Station, Ogden, Utah. k species to be planted. It has become necessary to know where a species will grow, what soils it prefers, what degree of drought or moisture it can endure, the nature and extent of its root-system, its susceptibility to insects and diseases, its weediness, its relation to other species, its use to the land- owner as a crop plant, and its value as food or cover for wildlife. Such information, approaching any degree of completeness, is remarkably difficult to get, and if it exists, must bo laboriously assembled, bit by bit end piece by piece, from many different and sometimes surprising sources, although botanists, nurserymen, landscape gardeners, horticultural! ft s , foresters and seedsmen have been gradually accumulating data of this sort for a very long time. It would therefore be absurd to say that we know* nothing of the uses to which the bulk of our trees and shrubs can be put. The mere fact that a species has been described and named tells us at once that something is known about it. However, we still lack much information that would make for more intelligent use of our native plants. WOODY PLANT REQUIREMENTS FOR EROSION CONTROL PLANTING Many workers arc of the opinion that a plant with a large root system will necessarily be the best one to hold soil in place. This idea is so uni- versally held that it may not be amiss to review briefly just what takes place when a soil is eroded, especially by water. In doing this, we may obtain a clearer picture cf how erosion can be prevented by planting vegeta- tion. In exceptional and rare instances, subterranean washing may take place but under ordinary conditions, the washing away of soil happens at the surface. It is the movement of soil particles downhill in water or into the air as dust that we wish to prevent.