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March 20, 1942


Subject:   (a) Specification for Plant Materials
(b) Shadows in Camouflage.

     1.     This camouflage bulletin comprises (a) a suggested specification for plant materials employed in camouflage, and (b) information pertaining to the handling of shadows in camouflage projects.

     2.     Requests for additional copies of this bulletin should be addressed to the Chief of Engineers.

            By order of the Chief of Engineers:

      C. L. Adcock,
Col., Corps of Engineers,
  Executive Assistant;
   Troops Division.




Procurement of Plant Materials for Camouflage.

     1.  In the camouflage and concealment of fixed installations, it is probable that large quantities of trees and other plant materials will be required. These plant materials differ from those normally specified in commercial practice, in that they may be of irregular shape and size and may have many flaws and defects, such as would render them unsuitable for civilian use. In the procurement of these materials, therefore, it is desirable that the specifications be written with the especial needs of camouflage in mind.

     2.  A suggested specification for plant materials for camouflage has been prepared by the Engineer Board, Fort Belvoir, Virginia, with the cooperation of the American Association of Nurserymen. This specification stresses only two major requirements: (a) the sturdiness of the plant stock, and (b) its effectiveness for concealment. A copy of the specifications is attached as appendix A.

Data on Shadows for Protective Concealment.

     3.  A knowledge of shadows is frequently of value in the practice of protective concealment. Shadows are usually of greater importance than color in the identification of targets and in the detection of camouflage by the aerial observer. A knowledge of shadows will permit the camouflage planner, when working with both new and existing structures, to locate shadows correctly, and to arrange for the absorption or concealment of actual shadows by artificial means.

     4.  Shadows can be simulated to a degree by the use of dark ground paints or stains. Such colorations must, however, be irregular in outline. They must be designed so that they will not disclose their falsity through the fact that they are static throughout the day. For example; the presence of a random hedge can be indicated by a dark splotchy strip across an open field. The edges must he irregular, however, and the strip should be somewhat wider than an actual hedge together with the shadow which it would cast.

     5.  Actual shadows falling upon absolutely smooth surfaces appear sharply defined to the aerial observer. Thus, to conceal the shadow of a target, consisting of straight edges, useful technique is to absorb the sharp lines of the shadow by means of planting shrubbery and trees. Shadows falling upon such planting are made to appear irregular, and the shadows of the plant materials themselves further add to the difficulty of identification.

     6.  The diagrams shown in appendix B have been prepared to indicate the general direction and length of shadows, at different localities,

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seasons, and hours of the day. By interpolation, shadow characteristics in latitudes and seasons not appearing on these diagrams, can be approximated within limits of possible error of 10%. It also will be noted that the normal method of considering north direction at the top of the sheet has been reversed because aerial photographs are generally studied with the sun at the top and the shadows pointing towards the bottom.

     7.  Diagram No. 1, Appendix B, indicates the method of using the data sheets. In making a study of any building or structure, a scale plan should be used with south at the top of the sheet; then the shadows should be traced for each of the high points of the structure in the proper direction, as indicated by Diagrams Nos. 2 to 6, for the particular latitude involved. To obtain the length of each hourly shadow line, the height above the ground of the point on the structure is multiplied by the "Length of Shadow" factor appearing in the last column of the chart. The isometric drawing on Diagram No. 1 illustrates the completed study for a small building. The upper portion of Diagram No. 2 indicates the approximate latitude of any given point in the two hemispheres.













          The bidder shall furnish and deliver as requested, all plant material as shown in the itemized proposal, in accordance with the following general specifications.

GENERAL:  Bidders are required to submit their estimates upon the following express conditions which shall apply to and become part of every bid received.

1.   All stock designated B&B shall be "balled and burlapped" in accordance with established practice.

2.   It must be noted on bid sheet whether stock is nursery grown or collected; and all stock must conform to the standard set forth herein. Wherever special specifications are not given the Horticultural Standards (1940 edition) adopted by the American Association of Nurserymen shall apply.

3.   When delivery by contractor is specified, it shall be understood that the contractor shall deliver the stock to any point in which the job is located as may be designated by the engineer in charge.

4.   All stock designated B&P shall be "balled and platformed" in accordance with established practice. All platforms used will be surrendered by this Department as soon as possible after trees are planted and may be obtained by permission of the engineer to whom they are delivered.

QUALITY OF PLANT MATERIAL:  All plants shall be healthy representatives of their normal species or varieties unless otherwise specified. They shall have well-furnished branch systems, together with vigorous normal root systems. Plants shall be free from all insect pests and plant diseases, sun scalds, fresh abrasions of the bark. All plant material shall comply with the State and Federal laws with respect to the inspection for plant diseases and infestation. If collected stock is specified, certificates shall be furnished indicating inspection by duly authorized state or federal inspector previous to digging. Any inspection certificates required by law to this effect shall accompany each shipment, invoice or order of stock, and on arrival the certificates shall be filed with the engineer in charge. Thin, weak, plants will not be acceptable. Plants must show appearance of normal health and vigor in strict accordance with these specifications.

          No substitutions shall be made without written consent. In considering substitutions, reference should be made to data included in "Plant Materials Commercially Available in the United States", published by Camouflage Section, U. S. Engineer Board, Fort Belvoir, Virginia, July 15, 1941.


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INSPECTION BY PURCHASING AGENCY:  Inspection of all plant material may be made at point of origin, point of delivery or both by an authorized representative. Stock which cannot be shown for inspection on twenty-four hours notice may be rejected. An inspection during digging will be made whenever such examination is deemed desirable. Final inspection will be made when the material is delivered as specified in the bid proposal, by the same representative. The Government reserves the right to reject or demand satisfactory guarantee or adjustment on all stock which is found unsatisfactory upon delivery.

DIGGING:  All plant material shall be dug with reasonable care and skill immediately previous to the shipment or if dug in advance, roots must be carefully protected at all times to prevent excessive drying and loss of vitality. Storage stock must be so designated. Special precaution shall be taken to avoid any unnecessary injury to or removal of fibrous roots. Each species or variety shall be handled and packed in the approved manner for that plant, having regard to the soil and climatic condition at the time and place of digging, the type of transit, and the delivery; and to the time that will be consumed in transit or delivery. All precautions that are customary in good trade practice shall be taken to insure that upon arrival at the destination, the plants are in good condition for successful growth.

BALLED AND BURLAPPED plants shall be lifted so as to retain as many fibrous roots as possible. All B&B plants must come from soil which will hold a good ball and be wrapped with burlap or similar approved material and tightly bound with twine or cord in such manner as to hold the balls firm and intact.

DELIVERY:  When delivery is made by the Contractor, all plants shall be packed in such a manner as to insure adequate protection against climatic, seasonal, or other injuries during transit. The roots of bare-rooted material shall be carefully protected with wet straw, moss or other suitable packing material which will insure the arrival of plants at the destination in good condition. Special attention shall be given for prompt delivery and careful handling in loading at the nursery and unloading at the point of delivery.

          The successful bidder shall make complete delivery within the time specified in the bid proposal.

          When calling for dormant stock, plants which are advanced to such a stage as to reasonably endanger their chance of living will not be accepted.


          The following specifications for various classes of plant material are supplementary to the standards of the American Association of Nurserymen, and shall apply unless otherwise specified.

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DECIDUOUS SHADE TREES:  Trees in which the leader or branches have been cut back or otherwise topped or dehorned leaving a stubby condition will not be accepted unless they have outgrown this condition.

SMALL OR FLOWERING TREES may be headed at any height required and are to be completely natural and free of stubs. Tree clumps shall have two or more main stems from a single crown at or close to the ground. Bushy trees shall be known as trees with branches from the main trunk close to the ground.

          In the matter of shearing, it should be kept in mind that if plants are properly transplanted and given room for natural development, they will not need as much shearing as plants not handled in this way. Plants which have been sheared into formal or topiary fashion will not be acceptable unless they have outgrown such shearing.

          Preference will be shown for plants which have been previously transplanted or root pruned at sufficiently frequent intervals to have developed a fibrous root system.

          All stock furnished must be true to name. One of each size must be legibly tagged with the size, and name of the material in accordance with "Standardized Plant Names", a catalog of approved scientific and common names of plants in American Commerce, adopted by the American Joint Committee on Horticultural Nomenclature.



*    These specific suggestions may, of course, be revised to fit the particular material wanted for any job.




National Archives & Records Administration, Seattle Branch
Record Group 181, Puget Sound Naval Shipyard Captain of the Yard Passive Defense Files

Transcribed by RESEARCHER @ LARGE. Formatting & Comments Copyright R@L.

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