In arrangement, the blossoms may be individual, as in the rose of Sharon (Fig. 33), or massed, as in the elder (Fig. 34), and this will affect the problem to a considerable extent. For use in gardens or near houses the odor must be taken into consideration, whether it be agreeable or unpleasant. Though the ailantus-tree is very decorative, care should be taken not to select the staminate form for use near the house, on account of the very disagreeable odor of the male buds.
The most interesting feature of a tree may lie in its twigs, because of their color or direction. This is vertical in the poplars, angular in the elm, horizontal in the Cratagus or the tupelo, and drooping in the weeping-willow and other trees of the type. Twigs may be slender, as in the acacia, or coarse, as in the Kentucky coffee-tree. The shape of the twig may attract. In the maple it is round, in the blue ash (Fraxinus quadrangulata) square, and in the Euonymus alatus triangular. The length of the twigs between branching is often marked, as in the ailantus or the elm.
Fruit characteristics have two phases, the economic and the esthetic. Each is affected by season, size, and color. The apple, cherry, pear, and plum are examples of economic fruit. The burning bush and the snowberry (Fig. 35) illustrate the decorative type. We may also have a combination of the practical and the esthetic, as in the common barberry and high-bush cranberry. The fruit is very decorative, and may also be used for the making of jellies and jam.
It is thus seen that the characteristic of a shrub is really one of the most important determining factors in its choice or rejection by the landscape-designer. The season in which the plant characteristic develops is always of importance, for by a critical selection a garden may be given year-round attractiveness by employing plants the characteristics of which develop at different seasons. The choice of plant materials will then give a constant interest, but an ever-changing one. It is therefore most essential, in choosing a planting scheme, to bear in mind whether the garden is to be used at one time in the year only, and to plant accordingly.
A very important consideration in the selection of plants is their value, which means lightness or darkness in the general impression, and is dependent upon the foliage, The full discussion of value may be found in the chapter on color.
For landscape purposes all three values, light, medium, and dark, may be used together with advantage, though it is not advisable to use extremes together. The light and the medium, or the dark and the medium, may be employed satisfactorily side by side, but the light and the dark, without intermediary, will produce too strong a contrast. In every planting scheme one value should be allowed to predominate.
The texture of a plant depends first upon the size of the leaves, then upon their number and arrangement upon the tree. The size of the leaves comes under three heads, fine, medium, and coarse.' The spiraea and the Japanese barberry are examples of the first variety, the Philadelphus and the lilac of the second, the Magnolia tripetela and the castor-bean of the third.
A plant is chosen for color on account of the hue it retains longest. This is known as its color characteristic. Plant colors usually change during the season. Consequently, the hue which is most generally present is known as the plant's distinguishing color. In the Siberian dogwood this would be red, because the bark retains its brilliant red throughout the year despite the greener summer foliage. An exception to color change is the Ker-ria Japonica, which is bright green in leaf and twig, and consequently retains the same hue throughout the year.
The soil in which a plant will attain its best development is often a determining characteristic.
It is very essential that all plants be grouped according to their soil requirements, for a delicate plant, no matter how necessary its color or form may seem to be for a certain problem, cannot be used if the soil is poor, and another selection from hardier material must be made.
As has been intimated, the architectural or horticultural emphasis must constantly be kept in mind in designing the development of any planting scheme. In the architectural style the interest depends upon mass (Fig. 36) in form, value, and color; while in the horticultural type the interest lies with the individual plant and its form, value, and color. The Faulkner Farm garden here shown is interesting for its forms and masses rather than for any flower color. For this reason it shows up well in black and white.
In undertaking a planting problem, the desired effect must first be carefully determined, and then the material selected that will produce the effect required. The landscape-designer wishes certain forms, sizes, and colors, and considers these essential to the best development of his problem. He may be able to achieve these results in many different ways by the use of a variety of plant materials, and consequently will have a considerable range of selection. The success of the result will depend upon the care exercised in the choice of the material, after taking into consideration the economic and esthetic requirements of the design.
The plan should always be read from the elevation. One often sees in parks and semi-public grounds that have not been skilfully laid out enormous beds of shrubs placed in such positions that only a very few are visible from any point of view, and consequently three-fourths of the material employed has been wasted, and is never seen at all. A wide bed containing shrubs of equal height may be seen to advantage from an elevation, or, if placed on a hillside, will look well when regarded from a plain, because it is possible to see the extent and shape of the planting mass as well as the shapes of the plants which compose it; but unless such a planting scheme is placed in a position where it can easily be observed from an elevation, it is clumsy and useless.
In all planting schemes, whether city, suburban, or country, and no matter what the type of planting employed, it is well to have a predominance of indigenous plants, or at least plants of the same general genus, possessing similar shapes, belonging to like species, and having the same general conditions of acclimatization. This predominating impression may be secured through the filler shrubs.
Figure 36. FAULKNER FARM Architectural planting with plant masses for principal Interest.
It is interesting to note that the contours of native trees generally harmonize with the topography of the locality in which they are found, the long axis of the foliage being parallel with the prevailing lines of the landscape. Thus the wide-spreading sycamore is found growing naturally on the plains, but the vertical, jagged cypress is thoroughly characteristic of the rocky hillsides of Italy. If either of these trees were to be found in the habitat of the other, it would serve as a most striking accent. The same tree may often be used in different ways in one planting scheme. For example, the highly individual shape of the Lombardy poplar compels attention when the tree is used singty or in groups of two or three; but it also may be planted so close together for use as a screen that the individual tree forms are merged, and all indication of accent is lost. The use of poplar-trees as accents is very noticeable upon the plains of France.
The harmonization of plant forms with geological structure is even carried to extremes by nature under unusual conditions. In the volcanic Japanese landscape shown in Figure 38 the contortions of the rock surfaces are repeated in the grotesque forms of the trees.
If one were to believe all that the untrained enthusiasts say about natural conditions and native planting, some very strange designs would result. One is told that plants should be only of the native and local varieties, and that they should not be corrected or trained, for "is not Nature the greatest artist of all?" Every one is familiar with planting schemes of this type, for they may be seen in any village where places have been allowed to go to ruin. They certainly look well in pictures, but are impossible to live with; straggling lilacs, unkempt trees, matted grasses, and a profusion of weeds, accenting the "native element," are seen on all sides, and are truly the logical outcome of just what the "back-to-nature" men are clamoring for. The entire question of selection of plant material is one of suiting the means to the end. Without judicious selection, any planting scheme will fail miserably.