As is the case with some of our other garden plants, some of the rock plants prefer a lime soil and others an acid-reacting soil, while still others appear to be entirely indifferent. In the lists given in Chapter XII, some of the lime lovers and some of the lime despisers are mentioned.
Unless the rock garden is to be constructed on a very generous scale, the matter of soil, while important, is not a serious consideration, for the comparatively small amount required may readily be made to order by the amateur rock gardener. Directions for this work are also given in Chapter VII.
LOCATION
Some of the rock plants like the full, blazing sun, others semi-shade, and still others do best in full shade. Still another group require full light, but a northern exposure only.
As it is not convenient to have the rock garden in several sections, located in several parts of the grounds, where these various conditions might be provided, the location selected for the rock garden should, if possible, be such that everything from full shade to full sunlight may be obtained. This may, to some extent, be provided for in the construction of the rock garden itself; but where existing trees, a northern slope, shade of a building, or similar existing conditions can be taken advantage of, they should be considered in selecting the site for the rock garden.
Other aspects of the location of the garden, such as its appearance in connection with the rest of the landscape planting, the desirability of having it in a secluded and protected spot, have already been discussed. The deeper and more constant the blanket of snow which may be kept over the rock garden through the winter months, the better. Not infrequently it is possible to construct it at the bottom of a ledge or bank, or upon a slope where the snows naturally drift deep and stay long. Where, by any chance, such a location is available, it should be taken advantage of, especially for the growing of the alpine varieties.