There are various spraying outfits adapted to the various requirements dependent on the amount of work to be done and the physical difficulties to be overcome. Probably the best small outfit for the amateur is the knapsack sprayer which can be easily transported and even carried up into the tops of trees if necessary. This consists of an airtight receptacle for the spray mixture, which may be strapped to the back in such a way as to easily allow the pressure to be kept up with one hand while the nozzle attached to a short length of hose is manipulated in the other hand. The best knapsack sprayers have a copper tank holding about four gallons of liquid, a brass pump, and an air pressure chamber which insures a steady stream. They weigh fifty pounds when full of liquid. A cheaper pump of about the same type but small capacity is the bucket pump which can be used with any bucket or pail. This is harder to transport about and not so satisfactory in other ways as a knapsack sprayer. There are various types of hand-operated barrel outfits. Sometimes the barrel is mounted on large wheels so that it can be easily moved about with a pump installed in the head of the barrel, or sometimes a larger hand-operated pump is mounted on a cart beside a barrel or tank. Such an outfit will take care of all but the tallest trees and is about the largest suitable for amateur spraying. It has enough capacity to take care of considerable spraying and enough pressure to insure a fine spray reaching all parts of even large plants. For occasionally spraying small shrubs and such plants as perennials and annual flowering herbs a small hand force pump is a very convenient one to have. These small pumps hold a quart of liquid in a glass or copper retainer.
The power sprayers are operated either by a gearing or sprocket and chain connecting the wheels of the outfit to the pump or by a gasoline engine mounted on a platform together with a pump and tank. When many trees are to be sprayed a power sprayer should be used in order to secure a pressure which will enable the forcing of a fine spray to all parts of the tallest trees. For spraying tall trees an apparatus which works up a pressure of two hundred pounds is required so that the spray mixture may leave the nozzle in a solid stream and break into a mist as it nears the top of the tree. This is not required for spraying smaller trees or bushes or flowers where the requirement becomes that of producing a fine spray a few feet from the nozzle.
Plate XII. Under climatic and soil conditions favourable to their growth, evergreens will produce a landscape picture incapable of reproduction through the use of deciduous plants. This photograph shows an effective use, under Long Island conditions, of arborvitae, red cedars, junipers, rhododendrons and yews as a background for a refined, formal pool. (See chapter IX)
Plate XIII. Carefully selected and planted trees for avenue and-street planting provide a uniform and a symmetrical effect together with the inviting shade, all of which are so essential to the standards of modern residential districts. (See page 116, group X-A)
Spray chemicals which are to be used in dust form are applied by means of so-called "powder guns" when large amounts are used on large trees. These are seldom useful on ornamental plants because of the usual proximity of houses or public streets and the consequent annoyance caused by clouds of obnoxious dust flying in the air. Many times, however, sulphur dust or hellebore can be applied by means of small hand force pumps adapted to using the dry dust, or this dust can be applied by sifting over the plants through holes punched in the container in which it is purchased.