Rocks calculated to simulate a natural stratification ought to be laid on an incline for proper drainage. Such pieces of rock may also be employed sparsely in wedging, and in the making of the so-called "pockets."
These pockets are of prime importance in the construction of a rock garden. They hold the only considerable spaces of soil and are the chief means of colonizing plants, thus providing for pronounced color effects. They should break the slopes and be irregular in size, shape, and distribution. The large ones may be easily subdivided by small stones when the planting is done if a further separation of species is desirable. The soil must slope a little from the top, so that there will be no standing water.
Cross-section of rock garden construction, showing shallow (A) and deep (B) soil pockets; tilting and wedging of rocks (C); bridging (D), and perpendicular crevice soil run (E). Two to three inches of soil between all joints. The lowest rocks are partly buried
The drainage of a rock garden is of vital importance. There must be plenty of moisture stowed away behind the rocks against the heat of summer, but all excess must be carried away. The garden should drain naturally, as the hills do. If any doubt exists, make a drainage bed of eight
inches of clinkers before starting to lay the stones.
The soil should be a good loam with a little peat, and stones varying in size from a mustard seed to an almond. A little manure may be used, but it must be old.