( Originally Published 1942 )
NO BOOK on cactus culture is satisfactory without a discussion of the rock garden. Such a garden is adaptable to a multitude of conditions, and it satisfies the eternal human longing to have something different. When you build a rock garden, you may be sure that no one else has one just like it, nor will they ever have one that resembles it except in a general way. It is almost impossible for two people to make rock gardens exactly alike because they are an intimate expression of the personality of the ones who build them, and as the personalities of the builders differ, so will the garden differ. It is possible to achieve such infinite variety in building the rock garden that it is neither practical nor desirable to give in detail possible arrangements. It is much better to indicate those general principles which must be followed to insure success, and leave the details of obtaining the artistic effect to the creative imagination of the individual.
It must be always remembered that good drainage is as fundamental a requirement in the rock garden as it is in all other types of cactus gardens—cacti cannot survive continuous wet feet. It is true that one may find wild cacti thriving in cavities of rocks with little soil and no drainage. Some time ago the author was in the Big Bend country of West Texas examining mortars made by an ancient Indian civilization. These mortars are holes drilled in the solid rock, and roots and herbs were crushed in them by using pestles of rock. The holes are usually about ten inches across the top, three or four inches across the bottom and vary in depth from very shallow ones to some that' are nearly twelve inches deep. In the bottom of one of these mortars situated in the top of a great rock was a baby Opuntia—healthy and happy. There was only a small handful of soil and no drainage except evaporation. The reason that it could thrive without drainage was because there was very little rainfall in that region, evaporation is very rapid and there are long periods with-out any rain at all.
If lava rock or some of the porous sand-stone rocks are used in the garden, the natural cavities and holes seem to be made especially for the planting of cacti. Such cavities may be used with telling effect, but drainage should be provided in sections where the rainfall is more than fifteen or twenty inches. This is especially important if most of the rainfall comes during the cold winter months. Even in the drier sections, these undrained cavities must not have much soil, because, if they do, the evaporation will not take care of the excess moisture—the bottom of the cavity will remain soggy for so long a time that it will be to the detriment of the plant.
Formality should be avoided. Much of the beauty of such a garden lies in the apparent confusion in the arrangement of rocks and plants, but that arrangement being always made with an eye for harmonious groupings. It would be almost offensive to see the largest rocks placed in the foreground and the smaller in the background of a garden which has practically a level surface. That would be almost as painful to the lover of the artistic as to see a garden with all the four-inch rocks and plants in the immediate foreground; behind them a band of six-inch rocks; next a group of those eight inches in height and so on to the ultimate background. It makes us almost shudder even to contemplate such an arrangement.
There should be the general effect of smaller rocks in the foreground, but of not such uniformity as to suggest artificiality. Larger rocks scattered here and there or an occasional group of them will secure the desired composition. The same discrimination may be used in placing the plants of different sizes.
It is often desired to build the rock garden so as to give the appearance of a little hill or a rough pile of rocks. It may be possible to take advantage of ground that has a steep natural slope. In gardens of this nature, the general rule is to place the larger rocks at the base of the incline which will naturally bring them into the foreground. This gives the impression of a heavier and more substantial foundation. The question as to whether such an effect is desirable depends largely on the steepness of the slope. A gentle slope does not suggest a conspicuous foundation, but a steep slope does.
There is another consideration which is often neglected by the amateur when he places the rocks in his garden. There is a grave danger of soil on a steep slope washing away during heavy rains or carelessness in watering the garden; and, after a heavy shower, one may find ugly gashes in the surface, plants with their roots exposed, and the soil completely washed away from between the rocks of the rock pile. The heartaches of such a tragedy may be avoided by so placing the rocks that water falling on a considerable area will not drain into one large, common stream which would have the force to carry the soil with it, but will be broken and rebroken into tiny rivulets as it flows down the side of the garden. It is only the swiftly moving water that causes the trouble. Some gardens are built with little terraces, using rocks for the walls. These terraces may have one end a little lower than the other making a slight incline so that the water cannot rush swiftly straight down the hill, but is carried gently along the length of the terrace before it runs off. The rocks of the rock pile may be placed so as to form pockets that will hold the soil, and they may also be laid so that they slant to the back and down. The water will then tend to drain into the soil instead of running down the side of the garden.
This problem of erosion is considerably simplified if the plants are left growing in the pots and those pots set among the rocks of the garden or buried to their tops in the soil. The pots keep the soil from washing away from the roots of the plants, but if the rocks are not properly placed, the soil may be washed from around the tops of the pots and that condition does not add to the beauty of the garden.
Those who have had experience with rock gardens usually try to select the plants that do well in that locality so they can be planted permanently in the garden. It is very inconvenient to lift and replace pots among the rocks, so that the number of tender and poorly adapted varieties are reduced to the minimum. There are very few localities in which a permanent planting may not be made if the varieties are selected intelligently. But whoever even heard of an owner of an outdoor cactus garden of any type who was perfectly happy with such a garden? There seems to be an irresistible desire to secure plants that are the most difficult to take care of; that require the most "babying." To the uninitiated this seems an illogical state of mind, foolish, almost a sign of weakened mentality—until they have a garden of their own, and then they are as bad or worse than the rest of us.
We may desire a delicate species because of an especially beautiful blossom; the plant may have a romantic appeal in that it represents distant countries utterly unlike our own, and it helps us to visualize its native haunts. And then, too, there is a bit of human nature at the bottom of this seemingly illogical state of mind. What a glow of satisfaction comes when you can show a fellow enthusiast the living demonstration of your understanding and skill in the care of your pets, and hear that highest of all tributes the sweetest of all words : "How in the world did you do it?" The pleasure, the joy, the thrill of such a moment repays abundantly the loving care and patient endeavor expended.
There are various ways of finding out which plants are adapted to the all-year sea-son of your locality. Perhaps the most satisfactory way is to ask your cactus-minded friends that live near you. Any reliable dealer in cacti will gladly give you information concerning any particular species in which you are interested, or will suggest other species which may prove satisfactory in your locality providing you furnish him with a detailed account of your seasonal conditions. It is important that you give the rainfall and its seasonal distribution. It is also necessary to give the maximum and minimum temperatures for summer and winter; and it would be helpful if you would furnish the average minimum temperatures for the critical winter months.
If your dealer lives in a distant section of the country and is not personally acquainted with the conditions in your locality, you must not be surprised if he makes some errors in his suggestions even though you may give him all the data listed above. There are many other factors which have a bearing on the selection of your plants, but the distant dealer has no way of evaluating them. One of the most important of these factors is your own skill and experience in caring for your plants in the garden. We therefore suggest that you search diligently close at home for the cause of any failure before you criticize the judgment of your dealer. On the other hand, you should hesitate to assume that you cannot grow some cactus in which you are interested simply because your dealer does not recommend it. If, after investigating the conditions in the native home of the plant, you still think that there is a possibility of its being a success in your garden, then the only way to satisfy yourself is to try it. You may be surprised at they number of times preconceived ideas are up-set by experiments of this kind. One failure does not prove that a thing cannot be done—perseverance is the keynote of success.
Experimentation is the result of that urge to follow untrodden paths, that innate curiosity to find out what may happen, that love of adventures into the unknown which gives to cactus culture its perennial lure.
Some gardeners prefer to have their gar-dens in the greenhouse where conditions may be under complete control at all times. Others feel that the greenhouse spoils the general effect of the garden, and many clever methods of protecting the outdoor garden against unfavorable climatic conditions have been devised. One very successful grower of Dallas, Texas, puts a tent over his garden during the winter. The high sides may be rolled up during pleasant weather, but lowered during the cold, wet "northers" of that section which are so destructive to tender cacti. A permanent ,framework about the garden, with a thatched roof, is approved by some. The sides are filled in with removable windows of glass or glass substitute during critical periods. A little ingenuity will give the framework a rustic appearance which may add to the attractiveness of the garden rather than detract from it. Partial protection may be all that is needed in some localities: a high wall on the side of the prevailing, unfriendly winds; or, a roof decorated with evergreen vines.
Plans may be worked out that will be adapted to your own conditions, and, in this way, the range of plants which you grow in your outdoor garden will be greatly in-creased with a very little expense.