A GARDEN’S THIRD DIMENSION—THE RETAINING WALL 
Adding a Feeling of Stability and Repose to the Garden Built Upon 
a Slope—A Plan to Distinguish Different Levels 
RICHARD H. PRATT, Landscape 
l rchitect 
^T^HAT garden builder is fortunate 
1. whose 'site lies upon some slope, 
however gentle, where he may have an 
opportunity to play, ingenuously per¬ 
haps, with one of the most fascinating 
elements of garden architecture. His 
garden need not be composed of a single 
surface, depending for its chief charm 
upon the arrangement of the beds and 
borders and the color and mass of the 
bloom and foliage, but will have a di¬ 
versity of levels; here and there a step 
or two or three up or down, and walls 
separating and supporting the higher 
portions from the low. For the straight 
line of even a low retaining wall will 
bring into the garden a feeling of sta¬ 
bility and repose and will create an at¬ 
mosphere of surprise and adventure as 
one ascends or descends from one height 
to another. . . , 
The low retaining wall rightfully replaces 
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the turf bank as the means of forming the break 
between two different elevations and, in sav¬ 
ing the space that would otherwise be a con¬ 
tinual annoyance, it becomes at once an inte¬ 
gral and important part of the garden. It pro¬ 
vides on its vertical surface another flower 
border upon which to arrange not only the most 
interesting of the Alpines and rock loving 
plants, but a great many of the most charm¬ 
ing perennials as well. It gives to the garden 
an air, withal, of having been not simply placed 
upon but rather built into its site. And we 
find William Robinson, the dean of English 
garden editors, discovering these several ad¬ 
vantages years ago when he quotes from his 
diary in“Gravetye Manor”, “Did away with the 
sloped border round the flower garden at the 
N. and W. sides and built strong dry walls of 
our own sandstone. Each stone was laid on a 
line of alpine and rock plants with the merest 
pinch of soil or sand under the plant. These 
retaining walls round the garden will enable 
us to have level borders instead of the sloping 
ones which starved in dry seasons, and will be 
in other ways a gain.” 
Wall Materials 
As the retaining wall in the garden may 
function both as a support for the higher level 
and as a flower border, great care and thought 
must be given to the choosing of its materials 
and to its construction. Let us consider then 
the materials of which it may be built. 
Stone comes first as the one 
that is generally the least ex¬ 
pensive, the most adapta¬ 
ble and the best in appear¬ 
ance. Of this material the 
definitely flat stone is the best 
and the round or hopelessly 
irregular the worst, for this 
reason: that the natural struc¬ 
ture of rock is one of rela¬ 
tively thin, level courses and 
it is the reproduction of this 
in building — long, hori¬ 
zontal, seldom broken lines— 
that gives the best effect; the 
effect, for example, that we 
get with brick. A wall with the stones laid too 
much at random lacks any feeling of repose, 
and one in which the stones are allowed to 
tilt off of level is just as restless. Stone, with 
its variance in size and shape, produces natur¬ 
ally throughout the wall fairly wide joints and 
here and there a niche, all suitable homes for 
plants that can thrive in such crevices. Its 
varying colors, too, give it a texture not to be 
attained in any other material. 
Brick is the next choice and would 
be employed where the proper sort of 
stone is not available and where the 
architectural style of a house, closely re¬ 
lated to the garden, demands its use. 
In the latter case and where there is a 
good local stone at hand, a combination 
can be made that will carry the relation 
of style and material through into the 
garden and yet allow the use of stone 
fn the walls proper. There copings, 
quoins and treads of brick will make a 
lovely effect and will give, at the same 
time, the desired result. A disad¬ 
vantage that brick has which does not 
occur in stone is that it may not be laid 
so securely without the aid of mortar; 
and a dry wall, with joints of loam, is 
not only the least expensive but the best 
for the growing of wall plants. 
Of the other materials there remain stuccoed 
hollow tile and concrete. Without intending 
any disparagement of either of these, both of 
which can be handled very attractively indeed, 
it is evident from their very nature that they 
do not afford a surface sufficiently broken to 
admit of any planting and must depend alto¬ 
gether upon plants growing below or overhang¬ 
ing from above. I heir use is the exception 
rather than the general rule and as a higher 
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boundary wall than as a low retaining one. 
Construction and Durability 
The retaining wall’s construction, both with 
regard to its stability and its utility, is of the 
greatest importance. The effects of frosts and 
of washouts must be carefully guarded against 
lest its first season find it bulged out of shape 
or a heap of ruins. If the wall is laid dry with 
joints of earth instead of mortar it must have 
a batter, or lean, toward the upper level of at 
least 2" in each foot of height. It will not 
stand long otherwise with any pressure behind 
it. 
There is no especial need for a foundation 
carried below grade, or rather below the front 
line, as the dry wall is fairly flexible and can 
give and take to a certain extent. Instead ex¬ 
traordinary care must be taken to ram firmly 
the earth behind each brick or stone as it is put 
into place so that there will be no tempting 
cavity for the reception of water and a resultant 
loose pocket in the wall. The bottom of the 
wall must rest, of course, upon solid ground 
even though, to do this, it is necessary to carry 
it quite a distance below 
grade. The actual construc¬ 
tion of the wall should be by 
someone skilled in the craft, 
but it would not be wise to 
leave all to this or that mason 
or bricklayer who does not 
generally feel the final effect 
with any too much assurance. 
The foundation of the wall 
with mortared joints must be 
carried down below frost line, 
as pressure on such a rigid 
structure at isolated points is 
very apt to crack the joints 
(Continued on page 54) 
