For bog plants in a rock garden, it is better to arrange one or more bays, in which the peat may lie in a level surface, because peat is unstable on a slope. An angle in the general structure may be cut off by a line of small rock pieces (not a straight line), and in that way a large pocket at the base level can be made, and the peat can be laid on a not too porous subsoil.

Bog plants demand a waterlogged home. If a water wall fountain or pond is associated with the rock garden, the place for bog plants is at the edge of the contraption, where the peat may be allowed to have actual contact with the water. When all the rocks are in place, and the result "when critically viewed is satisfactory, you should proceed to fill in all holes and crevices with compost, using a thin wooden blade, or bricklayer's trowel, to probe them and to ensure that the soil gets down to the lowest levels.

After the first heavy shower of rain you should go over the structure again, replenishing the soil where it has sunk in. If you have had to use brick waste as a substitute for rocks, your next task will not be an easy one because it is not possible to entirely disguise their character. Yet with a little ingenuity you may secure a very passable result.

The large masses will consist of many bricks cemented together in the burning, thus showing a decided, if rather artificial, stratification. You should place these pieces with their longer joints horizontal, or at such a slight tilt as you may decide. You may be tempted to so place them that their component bricks stand on end, with a view to taking advantage of the crannies between them, but that would be a bad arrangement.

There is no need to outline the back margin of the bank with rocks. The soil there may just run off into the level of the ground. When the structure of soil and rock is finished the gravel floor of the rock garden may be laid in the way directed for path making.

You should not use water-worn rock pieces which have a uniform pebble-like shape. Sometimes they have given a garden a grotesque appearance. On the other hand, a few rounded pebbles introduced along the margin of the rock structure are not out of place, suggesting, as they do, an old water course, and serving to retain soil washed down from the higher levels.

No special directions are needed for the practical work of putting the plants into the soil. It should be done in the same way as when planting a bed or border, and at the same seasons according to locality. You do need to have an ample depth of soil for some plants in a rock garden.

Discrimination should be used in selecting the plants for special positions. The smaller subjects like sedum, saxifrage, and sempervivum will thrive when rooted in crannies, and some on the porous surface of the rock itself, as witness the common house-leek. A few of these plants may be established at the margin of the rockwork and allowed to intrude upon the gravel within limits. They will soften the hard line where rock and gravel meet.

Plants of trailing habit should be put near the top of a miniature precipice, over which they will hang their flexible shoots and in due course paint its surface with brilliant color. Tall plants should go mostly to the higher levels. Give each plant elbow-room to allow for growth and expansion, but plant fully, so that when the plants are established there shall be little bare soil visible. Chinks in the vertical surfaces should not be neglected — they will carry their share of plant life, if care be taken to insert the roots and ram the soil well in contact with them.

Ferns will thrive in similar places, and, preferably, they should be located in the shady corners. The choice of plants is a vast one, but it is well for the novice to limit it at first to the hardier kinds, which are some of the most beautiful ones you will find. At the back of all, on the topmost level, small flowering deciduous and evergreen shrubs may be associated with tall perennials like starwort and snapdragon.