This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
In the chapter on Climate will be found some information respecting the countries which furnish the greater part of the exotic plants hardy in Britain. The few remarks to be made here refer to the classes of hardy plants inhabiting different regions. Every part of the world has what is termed its characteristic vegetation, depending to a certain extent upon climate and soil, but probably more upon other causes which have been variously explained by different investigators. We have only to speak of facts as they are, without any speculations as to the agencies which have operated to bring them into existence. Experience teaches us that plants are not by any means distributed and confined, in a wild state, to localities best suited to them, or where alone they will flourish. Frequently we find that plants attain a development unknown in their natural state, when conveyed to a distant part of the world possessing a similar climate. This may be attributed, in a great measure, to freshness of soil. In our Australian colonies, for example, many of our common weeds have been introduced with grain and cereals, and in many instances where they have escaped beyond the limits of cultivation, they have taken complete possession of the soil, to the total exclusion of the native vegetation. In course of time the vigour of these introduced plants diminishes, and they are gradually reduced to more equal terms with the native plants. This fact supplies a valuable hint to the cultivator respecting the importance of change of soil, and explains the relative fertility of freshly-broken land. But this is a digression: we were about to speak of the different classes of plants characterising the vegetation of various regions possessing a similar climate to our own. Taking first of all the Coniferae, the members of which, with few exceptions, are evergreen, we find that the majority come from North America, especially the north-western regions, between 40° and 60° N. lat., and Japan. From North America we have the gigantic Sequoias, the stately Piceas and Abies, and many species of Pinus, together with some of the handsomest of the Cupressineae. Japan and Northern China furnish us with many beautiful forms of Biota orientalis, several species of Juniperus and Retinospora, and the peculiar forms illustrated by such species as Cephalotaxus drupacea, Thuiopsis dolabrata, Sciadopitys verticillata, Salisburia adiantifolia, Cunninghamia Sinensis, and Cryptomeria Japonica. In addition we have the hardy European species, a few from the mountains of India and Mexico, and one or two outliers, like Araucaria imbricata and Fitzroya Patagonica, from South America. Most of the Mexican species are too tender for our climate; but India furnishes us with a few of the handsomest species in cultivation, as, for example, Cedrus Deodara, and Pinus excelsa. Evergreen trees and shrubs not belonging to the Coniferous tribe sufficiently hardy for cultivation in the open air, are chiefly from the South of Europe and Japan. As examples of South European species we may name the Sweet Bay, Laurestine, Portugal and Common Laurels, Evergreen Oak, Phillyrea and Heaths. The Japanese region contributes the well-known Au-cuba, numerous forms of which have recently been introduced, Euonymus, Eurya, Berberis, Ligustrum coriaceum, and several others, most of which, however, are too tender, except for the warmer parts of the kingdom. Asia Minor contributes Rho-dodendron Ponticum, and North America, and the mountains of India are the native countries of most of the other cultivated species of this beautiful genus. Kalmia, and several other less important Ericaceae, are from North America. South America contributes Berberis Darwinii and other species, Escallonia species, Pernettya mucronata, Fabiana imbricata, Lardizabala biternata, and the quasi-deciduous Buddlea globosa. The eastern and central regions of North America are as rich in deciduous as the west is in evergreen trees, including numerous Oaks, Maples, Hickories, Chestnuts, and several Magnolias, Limes, Elms, Poplars, Robinias, and the Tulip Tree. Shrubs cultivated mainly for the beauty of their flowers are also abundantly represented in North America, e.g. Spiraea, Ribes, Philadelphia, Azalea, Ceanothus Calycanthus, Crataegus and Bignonia. Japan furnishes us with the beautiful Deutzias, Diervillas, Hydrangeas, Pyrus Japonica, Kerria, Forsythia, various species of Clematis, etc. From the South of Europe and Asia Minor we have Azalea Pontica, Hibiscus Syriacus, Cercis Siliquastrum, various Cisti and Leguminosse, including the Laburnum, several species of Cytisus, Genista and Spartium. Siberia and Northern China furnish us with several noteworthy . outliers of different families, whose members are chiefly natives of warmer regions, such as Koelreuteria paniculata, Ailanthus glandulosa, Xanthoceras sorbifolia, Phellodendron Amurense, Eleutherococcus senticosus and Fortunaea Chinensis : with the exception of the first two, these are recent introductions. Caragana and Halimodendron are two very hardy genera from Siberia. Some of the foregoing extend to Japan, and we have also many other very handsome, though mostly tender, deciduous trees from the same country. Sophora Japonica is the best known and the hardiest of them. The beautiful forms of Acer polymorphum are, unfortunately, too tender to withstand the winters in the greater part of Britain. Amongst the remaining deciduous trees from Japan, we may name the genera Ulmus, Planera, Pterocarya, Melia, Rhus, Broussonetia, and Salix. There are few trees or shrubs from Australasia hardy enough to withstand the climate of any part of the kingdom, with the exception of the Scilly and Channel Islands. Herbaceous vegetation characterises nearly all temperate regions, but more especially the northern. The proportion of woody to herbaceous species is much higher in the southern hemisphere, and the general appearance of the majority of the herbaceous species is very different to what we are accustomed to in our native plants, even in species belonging to European genera. Although there are no hardy shrubs from New Zea-land, some of the herbaceous plants will succeed in the open air with us, as they are less exposed to the effects of sharp frost; but very few are grown, being for the greater part more curious than beautiful. Libertia ixioides is from New Zealand, and the magnificent Chrysobactron Rossii is a native of the Auckland Islands. Myosotidium nobile is, so far as at present known, peculiar to Chatham Island. Doubtless many other species would prove hardy in the south-western parts of the kingdom. The temperate parts of South America are also barely represented in our borders. Geum Chiloense, Loasa aurantiaca, Fuchsia macrostema, and the less known, somewhat tender Grunnera scabra, are the nearest approach to hardy subjects from that part of the world. South Africa, although nearly 20° farther north, contributes many more species than South America. They are chiefly bulbous plants, or belonging to the Liliaceae and Irideae, to which we shall allude again below. Classifying herbaceous plants according to duration and hardiness, we shall see whence we obtain the greater part of the more familiar species.
Annuals, hardy and half-hardy, find their maximum in California and Mexico, where they are exceedingly numerous and diversified. A reference to the following orders will be sufficient to give an idea of the richness of this region in plants of annual duration. Papaveraceae, Cruciferae, Onagrarieae, Com-posite, Polemoniaceae, Hydrophyllaceae, and Scrophularineae. The region ranking next in order of richness is the Mediterranean - South of Europe, North Africa, and Asia Minor. As examples we may mention: Candytuft, Virginian Stock, Mignonette, Convolvulus tricolor, Larkspur, Sweet Pea, Common Marigold, Ten-Week and other Stocks, and Lavatera trimestris. In addition there are numerous species belonging to the Caryophylleae, Cruciferae, Compositse, and other orders. Australasia furnishes a few half-hardy, the most noteworthy of which are those bearing 'everlasting flowers,' belonging to the genera Helichrysum, Helipterum, Waitzia (Morna), and Rhodanthe, all members of the Compositae. Chili also contributes a few half-hardy species, as Portulaca, Calandrinia, Salpiglossis, Schizopetalon (hardy), and Schizanthus. From South Africa the number is still more limited, and none of the species are in general cultivation. Mesembryanthemum tricolor, Kaulfussia amelloides, Heliophila spp., Grammanthes gentianoides, and Venidium calendulaceum are natives of that region. Japan and China, both so rich in ornamental evergreen trees and shrubs, and perennial herbs, add scarcely any remarkable species to our list of annuals. Callistephus hor-tensis, the China Aster, is, however, an important exception.
For the rest, we have a few odd annuals from India, Northeast America, and the tropical regions of South America, and various parts of Europe and Northern Asia; for example, Amaranthus spp. from India, and Tropaeolum spp. from South America.
Biennials, as a class, are not very numerously represented in gardens, and the majority of them if sown early will flower the same season, though in a natural way the seed would germinate soon after it is shed in autumn. They occur in all regions where there is herbaceous vegetation. The principal species are enumerated with the annuals, at page 617.
Perennial herbaceous plants, as we have stated above, are very abundant in almost all parts of the temperate regions of the northern hemisphere. Those termed Alpine plants, that is, growing in mountainous districts at a considerable altitude, are strongly represented in Europe. Indeed, by far the larger proportion in cultivation are natives of the Alps proper and the Pyrenees. Returning to the plains, North America stands perhaps in the foremost rank; but as many of the species are of comparatively recent introduction, they are not so rich in garden varieties as those belonging to the Old World. The following are some of the better known genera : Phlox Pentstemon, CEno-thera, Aster, Lilium, Lupinus, Aquilegia, Spiraea, and Helian-this; to which might be added many others belonging to the Malvaceae, Compositae, Scrophularineae, etc. Besides the Alpine species alluded to above, Europe furnishes us with a large number of our familiar perennials; and, if we include North Africa and Asia Minor, we have a considerable proportion of those in general cultivation: Anemone, Ranunculus, Wallflower, Carnation, Pink, Paeonia, Auricula, Hyacinth, Hollyhock, Campanula, Chrysanthemum (Pyrethrum) roseum, Myo-sotis, Violet, Pansy, Tulip, Crocus, Narcissus, Antirrhinum, Saxifrage and Lilium, will serve to illustrate this region. Japan and China, taken together, offer many curious and interesting species. And from these countries we may mention that we have a large number of garden varieties, not only of herbaceous plants, but also of shrubs introduced by various travellers. The most important genus is Chrysanthemum. Spiraea palmata, Dielytra spectabilis, Paeonia Moutan, Primula Japonica, Anemone Japonica, Lilium auratum, and several other species; Funckia, Aspidistra, and Bocconia make up a list of attractive plants. South Africa contributes a large number of bulbous plants, belonging chiefly to the Irideae, Liliacea, and Amaryllideae. The magnificent hybrid Gladioli in cultivation are the offspring of South African species. Kni-phofia aloides (Tritoma uvaria) and Agapanthus umbellatus are two valuable plants from the same country. South America furnishes very few beyond those already mentioned; but we must not forget to mention the noble Pampas Grass (Gynerium argenteum). India is also poorly represented in our gardens, though many of the mountain plants are quite hardy.
The geography of the tender species employed for summer bedding does not come within our province, but nearly all of them are mentioned or described, and their native countries given in the body of the work.