The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California

American Rock Gardens

FIG. 4.—ORIENTATION OF ROCK GARDEN

Again, the requirements of many rock plants make necessary further choosing in the kind of stones to be used. Some plants grow best in an alkaline or lime soil. For these a lime rock, as marble or coral, should be used if available, or else lime rubble is mixed with the soil. For those which hate lime and demand acidity in the soil, a hard rock, (as granite) is needed, with plenty of peat fibre in the soil. Fortunately, many rock plants are neutral in these requirements.

While the stones are being gathered and hauled to the site, it is well to get the soil ready also. Ordinary garden soil will not do at all, nor will the best of garden soil—far from it! A soil that will raise prize lettuce is a fatal dose for alpines. While it might be said that each kind of rock plant requires a special mixture for its best diet, the general foundation for the majority of them is one-third sharp sand, one-third vegetable fibre, and one-third garden loam. These may be gathered separately and mixed just before being used. The ideal natural soil is the top sod of stony pastures, long rotted, and screened to take out roots of weeds. The sand should be sharp and gritty, even rather coarse, and never fine river sand or that containing clay. It is porosity that is required, and sifted hard coal ashes may be added, especially for lime lovers, like Dianthus.

The vegetable fibre may be from any source so long as it is well decayed,—old sod, leaf-mold, or turf from the woods. The best is peat from the bog piled a year ahead, pulverized by the frost of one winter, and dried by the sun of one summer. Then it will break into small pieces and is surely free of weed seed or roots. For city gardens it is most convenient to use any of the prepared peat fibres, as these are well ground and free from weeds. In any except special spots the coarse grades are better than the fine. The garden loam should be free from clay and not of very fertile nature. It gives body to the mixture, the sand being porous and the fibre water-holding. The great danger is the presence of roots and seeds of common weeds, which soon will cause great trouble. Screening through a sieve will take out the roots of weeds, but the seeds will have to grow to their next stage. No fertilizer is ever added, save perhaps a little bone meal. Barnyard manure, in any stage, is forbidden, for it is too rich a diet for rock plants and is the original home of all weeds.