Alpine plants
- Plants that grow above the tree line on mountains, usually covered in snow in the winters.
- Loosely used to refer to any plant grown in a rock garden.
Alpine plants are often grown in rock gardens and Alpine houses.
| Standard Cyclopedia of Horticulture |
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Alpine Plants. In gardening, a term used to designate those plants that thrive in imitated alpine conditions,—in cool places of short-growing season and abundant cold-water supply in the growing and blooming period, and soil conditions approaching those of mountains; in practice, alpine-gardening is a form of rock-gardening. The cultivation of alpine plants in some parts of the United States must always be attended with difficulty. Wherever, as in the coastal plain region of the Atlantic seaboard, the summers are long, dry and hot, it is almost impossible to cultivate many of the most desirable alpines. A study of the natural environmental habitats of alpines is the very best way to arrive at really valuable ideas upon their cultivation. Excluding all those alpines of apparently little definite habitat preference, such as the snowdrop, daffodil, poet's narcissus, trailing myrtle, Christmas rose, and Scotch pink, all of which are true alpines, but also tolerant of quite ordinary garden conditions, there is a large class, some hundreds of species, that will grow only in situations approximating their native habitat. These plants, some of which are perhaps the most beautiful flowers in cultivation, grow usually in a region haying long, rigorous winters, a growing season averaging 100 to 120 days, and a constant supply of moisture which, on account of its source in the snow above the vegetation-line, is always nearly ice-cold. It is true of most of these alpines that they grow among the rocks, and, as we shall see presently, this is a factor that must be reckoned with. Many of them grow in the open sun and are exposed to violent, often bitter, winds. Others again are on north-facing slope's, where the sun rarely, if ever, reaches them. A partial list of alpines given below will show the preference of some of the more common species with regard to the exposure to sunlight. Localities in the United States and Canada where alpine gardens may be tried with a fair measure of success. One of the basic requirements of most true alpines is a short growing season. The Atlantic seaboard from Nova Scotia southward, east of the "fall line" (the flat, usually somewhat sandy, regions between the eastern fringe of the Alleghanies and the sea, such as southern Long Island, southern New Jersey and all south of it except parts of Virginia, North Carolina, South Carolina, and Georgia), has an active growing season of 170 days and upward. This is computed by adding the days from the last frost of spring to the first frost of autumn. At New York, the season is 210 days, at Philadelphia, 220 days, and of course constantly increasing southward. On account of this long growing season and also because of the dry, hot character of the winds, it is almost impossible, without great expense, to maintain an alpine garden in this region. The same is true of the coastal part of the Pacific coast, and in the Mississippi Valley up to about St. Louis. This is, of course, a general statement, and peculiarly favorable local conditions within the areas specified may be found, where the attempt can be made. But it is extremely doubtful whether any really good alpine garden can be maintained within this area permanently without a great maintenance expense, in the way of constantly supplying new plants, keeping the garden regularly cooled down by water and the like. As one goes back from the coast, even a few miles, there is a marked change in the climate, and particularly noticeable is the constantly diminishing length of the growing season. Near Hartford, the Highlands of the Hudson, northern New Jersey and Pennsylvania, the growing season averages from 138 to 120 days, more or less. As a general rule it may safely be stated that anywhere east of the Mississippi where elevations of 1,000 feet or greater are found, an alpine garden is permissible except in the southern Alleghanies, where greater elevations must be sought. This length of the growing season is easily computed for all parts of the country, as indicated above; and wherever we find an active growing season of 100 to 140 days, it would be profitable to make an alpine garden. In the East it will be found that the short season is almost always correlated with elevations in excess of 1,000 feet and in the West at several times that altitude. Position of the alpine garden. So far as our purpose is concerned, there are three classes of alpine plants: (a) those that require full sunlight, (6) shade-inhabiting species, and (c) those that are apparently indifferent as to exposure. To meet all these conditions within a single garden is not always possible, and a selection of plants must therefore be made, unless one is fortunate enough to have a situation that combines these requisites. As a general rule it is better at some distance from a dwelling, stable, or garage, both architecturally and culturally. No class of plants is quite so wild as alpines, and the more secluded the garden, and the greater the suggestion of sequestered nature the better. A screen of evergreens or other trees, and a northward-facing slope, insuring good drainage, is perhaps the best all-round combination that one could desire. If the garden is at a slight elevation above the immediate surroundings, so much the better; although this is not absolutely essential. Southern or western exposures are to be avoided unless the garden is at least 4,000 feet above the sea in the East, and from 6,000 to 8,000 feet in the West. It should also be arranged so that drainage will not be entirely down through the soil as in ordinary gardens, but rather so that the water can trickle from the roots of those above to those below. This is often best attained by a judicious use of rocks, which will be considered later. Making the garden. Having decided that one lives within the area in which it is safe to begin the installation of an alpine collection, the next most important consideration is to give the plants the requisite local condition. Nearly all of them require good rich soil, at least 18 inches deep, preferably deeper. Even those species that grow in the crevices of the rocks in their native habitat do so not because they "like" such situations, but most probably because no more favorable place is available. In preparing the soil, it is well to remember that at least one-third of the mixture should be fine rotted leaf-mold mixed with equal parts of loam and sand. The latter is quite necessary in order to insure perfect drainage. It has been stated that some alpines will thrive in situations that approximate our bogs in having a high humic acid content. But most of the species thrive where the drainage is good and the soil is sweet, not sour. If for no other reason than to insure perfect drainage, it is best to construct the garden in a series of terraces with walks of more or less irregular outline between, as taste and convenience dictate. Avoid all semblance of formality in the arrangement of these terraces, as artificiality or formalism in the alpine garden are quite the least desirable features to be sought. The terraces, or any modification of them, are best held in place by a more or less free use of rocks. The placing of these requires great skill and taste, as their purpose must be twofold—to add a sense of naturalness to the garden and to make suitable pockets in which to grow the plants. While it is true that many alpines, such as Thalictrum aquilegiaefolium, Clematis recta, Aconitum Lycoctonum, Digitalis ambigua, Polenumium caeruleum, Gentiana asclepiadea, and Delphinium elatum, with many others, can be grown without the use of rocks, it is true, on the whole, that most alpines grow better and seem more at home when rocks are part of their environment. Just what part the rocks play in the home economy of the plants is not very well understood, but the readiness with which they conduct the water to the roots, and their tendency to keep the soil cool both suggest themselves as possible benefits. For such species as Phlox Douglasii, Cassiope Mertensiana, Polemonium montrosense, and all plants of their type whose natural home is at elevations from 10,000 to 12,000 feet, care must be taken to insure almost constant sub-irrigation of cool water. In their native habitats, such plants have their roots constantly in the icy water of the substratum, and any conditions that do not approximate this will make failure almost certain. An arrangement for insuring this sub-irrigation is figured in Fig. 174, diagramatically. The pocket of soil in the rocks having been filled with the proper soil mixture, the water may be let in at a, with a rock just in front of the pipe to insure the water's downward passage (d). With the bottom made water-tight by concrete or rocks and clay, and the outlet regulated at 6, a definite water-level can always be maintained at c. The outlet can be arranged as indicated to flow either over the surface of the rock below or in a pipe behind it. If the water for this plan comes from a cool spring, so much the better. The smallest stream of water is sufficient, as it is not the water itself with which one is aiming to supply the plants, so much as the cooling of the soil, rocks and atmosphere that ensues from a gentle flow of water through and around the soil and rocks. Such measures are not necessary for all alpines, hut a few species must be grown under conditions approximated by these methods. The expense of installing and maintaining such construction, however, is relatively great, as compared with the simple arrangement of the rocks in pockets, overhanging ledges, nooks, and so forth, which is all that is required for the great majority of alpines. A common and particularly undesirable method of procedure is to tumble a great mass of rocks together, usually utterly without form or definite purpose except to look "artistic," then pile soil amongst them and plant the whole mass. If the idea is constantly kept in mind that the rocks are for use primarily, that they are cultural necessities, and that plants naturally grow between, and among, and often half underneath them,—then the final result is likely to be beautiful, because they are useful and have been placed with an eye to their sole raison d'etre in the alpine garden, which is to be a home for alpine plants. In placing the rocks, indeed in the arrangement of the garden generally, it is better to avoid situations in which the drip from overhanging trees or other objects will fall on the plants. No plants are specially benefited by drip, and alpines, particularly those having tomentose leaves, will suffer from such treatment. Plants for the alpine garden. Unfortunately, very few American dealers carry anything like an adequate stock of alpine plants, and only the commonest and best-known species are to be found in the American trade. This has had the effect of restricting the popularity of alpine gardening in this country, and, furthermore, all the alpine gardens of any size have had to seek in Europe for the large variety of species that constitute a well-stocked collection. Many European firms, particularly in England and France, have specialized in alpines. At least 1,000 species are offered by one continental dealer alone. A common but altogether unsatisfactory method, and one that has resulted in numberless failures, is the attempt to import plants direct from these dealers. The time of transit, the highly specialized character of the cultural requirement of alpines, and the lack of attention during transit, all operate to make such shipments costly and usually unsuccessful. The best and most satisfactory method is to buy seeds of the plants to be cultivated. The initial cost is less than one-fifth and the personal satisfaction in having grown one's stock of plants more than offsets the time spent in this work. The seeds should be imported early in the spring or even in the late winter for those with greenhouse facilities. Sow the seeds in pans or boxes in a light soil of leaf-mold and sand in about equal parts. It is best partially to shade the seeds and very young seedlings for a few days. Pot up when the seedlings are stout enough to stand the transfer, which of course, varies with different species. If it is inconvenient to place them in their permanent home the first year, they may be repotted and then the pots plunged in ashes in the frame. With proper shading from the intense sunlight, and a plentiful supply of cool water so that the ashes arc kept moist and cool, they will grow very well under these conditions for the first year. Many of the species can be grown always with this treatment if one has no garden ready for them. The shading for these frames is easily made of ordinary plasterer's lath, the strips being placed about one inch apart and the whole shade arranged so as to be about 2½ feet above the surface of the ground. Of all the genera cultivated as alpines, the most important are the gentians, saxifrages, sedums, a few dwarf primulas and the pinguiculas. These are much better known abroad than in North America, but many of the best of them can be grown in this country. Among the gentians, Correvon of Geneva classifies them for cultural purposes as follows: 1. Calcareous-soil gentians requiring sun: alpina, angustifolia, Clusii and Kochiana. 2. Sphagnum-moss' species: bavarica, Rostanii, septemfida. 3. Marshy-ground species: angustifolia (also in group 1) asclepiadea, Pneumonanthe. 4. Peaty sand and sandstone with peat in it: alba, Bigelovii, ciliata, frígida, Parryi, pumila, Wailichiana. 5. Of indifferent habitat preference: brevidens, cruciata, dahurica, decumbens, macrophylla, Oliveri, Saponaria, scabra, straminea, Weschniakawi. Among the saxifrages only the dwarf, usually perennial, kinds are grown as alpines. In moist, rocky places in the alpine garden the following species of pinguicula will be useful: P. vallisnerifolia, P. grandiflora, with purple and blue flowers and P. alpina with white flowers. P. vulgaris and P. lusitanica may be grown in general situations in the "alp." It is often necessary to make a definite selection of species for a sunny or shady place, as most of our alpines cannot be grown without reference to the amount of sunlight. For those who can arrange only for a rather sunny situation, in which the amount of shade is not sufficient to keep the soil and rocks cool, the following will be found helpful: Alpines For Sunny Situations. To these may be added the native species that grow naturally in America at elevations in excess of 1,500 feet, such as Coptis trifolia, Cornus canadensis, Clintonia borealis, Tiarella cordifolia. Trillium grandiflorum, Claytonia caroliniana, Dalibarda repens, Polemonium VanBruntiae, various terrestrial habenarias, Mitella nuda, Arenaria groenlandica, and many others. The plants both for shaded and sunny situations will grow better if there is a liberal top-dressing of leaf- mold and sand, about half and half, applied each spring. It will be noted that all the plants listed in both lists are perennials. Most natural alpines are of this type, the shortness of the growing season precluding the possibility of the full development of an annual. For those who wish to go into the growing of alpines more extensively, a partial list of the alpine genera together with an indication of the number of species that are to be found in the principal European trade catalogues is appended. Many additions will suggest themselves as the alpine gardener becomes better acquainted with those listed below and their relatives. List of the chief alpine genera. The figures indicate approximately the number of species in each genus that are alpines. The literature on alpine-gardening, in English, is very meager. Any good book of the flora of high mountain regions,—and there are a dozen or more excellent works on the flora of the Alps,—will aid in the way of suggesting new species that may be grown. A good but rather out-of-date book on the making and culture of alpine gardens is A. Kerner's "Die Cultur der Alpenpflanzen." A useful work containing many cultural hints is H. S. Thompson's "Alpine Plants of Europe, with Cultural Hints. The first International Congress of Alpine Gardens met at Naye, Switzerland, in 1904. As yet nothing except administrative reports of this convocation has been published.
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