There are two ways of planting a rock garden. One is to do all the crevice planting along with the building, and the other, of course, is to defer everything until the rocks are in place and the soil thoroughly settled.

The former plan is a singularly appealing, as well as practical, one. There is something fascinating in finishing completely a part of the work as one goes along. The practical advantage lies chiefly in the fact that by this method good-sized plants may be firmly established in crevices at the very outset. The soil in that case should be put part way in the crevice and packed down. Then some loose soil sprinkled on top, and the plant, with the earth well shaken from the roots, unless it has a tap root, laid down horizontally with the crown just outside the edge of the soil. Next spread the roots to follow the soil run; fill up the crevice with more soil, packed well, and follow with more plants of the same kind. Use small stones to wedge plants where it appears necessary. Plants that hang down should be placed in the higher crevices; this must be all thought out beforehand.

As a matter of fact, the planting plan cannot be too thoroughly thought out in advance. At point after point it dovetails with the structural plan, which must accord with the requirements of what may be called the more difficult rock plants—the alpines, some of the ferns, and those plants that fit in well with rock work but demand more than the ordinary garden moisture. The best way is to decide what plants are most desirable in the circumstances, omitting, as a rule, the difficult or "finicky" ones; there will be plenty of time to experiment with those when you have more experience. Make a face plan of the several sections of the rock work and mark on it where the plants are to go. Use numbers, each corresponding to a species.

The general idea is that all the soil shall be concealed, not necessarily at the moment of planting, but at the end of one or two seasons' growth. Unless you are a collector, variety is of little importance. The main thing is that there shall be beauty as a whole, a few marked seasonal effects of color with massed bloom and some green the year round; the garden must never be bare at any time, as nature will show you. Plants clustered here and single there is a good planting rule. Colonies, always of marked irregularity, ought to merge into one another, but they should not so overrun the rock work that no stones are in sight. Not infrequently some of the best effects are obtained where more rock than flowers is seen. A boulder, for example, calls for the contrast of plants, perhaps only a few low-growing ones in a natural pocket, rather than a semi-eclipse. As a rule, plant one hundred of half a dozen or so suitable, and easy, species in preference to fifty or more kinds.

Study at the same time the form of the plants that are to be used; some quickly resolve themselves into a carpet, some never get beyond mere tufts, some always grow straight up, some prefer to hang down, and some have foliage that is evergreen or nearly so. To be more specific, one plant of Saponaria ocymoides will spread out over four square feet of soil, and thus fill completely a moderate-sized pocket, whereas to conceal the same amount of ground three dozen auriculas might have to be used. The same is true of the white rock cress (Arabis albida). So, too, with a crevice. A single plant of one of the trailing stonecrops would fill it, perhaps, when a number of rosettes of the smaller kinds of house leek would be called for.

Tall plants, like the foxglove, may sometimes be used, in a small group, at the end of a bay on the level of the path; but they are best placed behind the rock work, as a background, or as dominating features of the entrance or exit of the garden. At the entrance or exit such bold plants make a good bridge between the rock garden and the outer grounds. Spreading and trailing plants should be placed a foot or more above the path level and most plants with tufts or rosettes of foliage. If the path is broad enough some of the wide-spreading plants may go at the base of the rocks, but the rule there is to use those of moderate spread, with a few tufted plants and some that grow upright, but are not tall, to lend variety. When the path is of flat stones, irregular in both size and placing, this growth should fill all the soil space—even between the stones. Such a path will be found more than worth while, and not as much of an undertaking as it may seem.

Obvious considerations are that plants with a decided hankering after moisture or shade should be favored in the matter of location, though it is astonishing how adaptive many of them are.

Do not plant the weak next to the strong. Unless you are a gardener of eternal vigilance, the weak will have the worst of it before you realize what a mistake you have made.

Finally, do not forget that planting is not the end; it is only the beginning—of planting. So long as the rock garden exists there will always be planting. Normal mortality will necessitate some, there will be thinning out, and time will suggest additions and more or less rearrangement.

And with the planting goes on the continual care, much of which can be done in the course of the daily walk in the garden, and therefore the loss of time will not be felt. Water in case of a real drought, but use a sprinkler, and do not stop until the ground has been soaked to a depth of a few inches. Mere surface watering is bad enough in the ordinary garden; in a rock garden it is a fatal error, as the growth of roots near the top of the soil leaves the plants in no condition to stand the full force of the summer sun.

Go over the garden thoroughly once a year and all the time keep a sharp lookout for weeds. If the soil is heavy, top-dress with grit in the fall. Grit is good for rock plants. Stone chips placed around a plant will prevent too much dampness lodging about the collar in winter. Watch out for weak spots after very heavy rains.