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 nearly all parts of the temperate zone of the northern hemisphere there is a great preponderance of the herbaceous over the woody vegetation, and we have scarcely any hardy plants from the southern hemisphere. Hence it follows that we have a very much larger number of species to select from in this division than in the woody, and by judicious selection we may ensure a continuous display of flowers from early spring till the end of autumn, whilst a few cold-defying species serve to enliven the winter months. Several large orders consist almost exclusively of herbaceous plants. This will be seen on reference to the Ranunculaceas, Papaveracese, Cruciferse, Caryo-phylleas, Malvaceae, Composite, Campanulacese, Polemonia-cese, Primulaceae, Grentianaee, Scrophularineae, Convolvulacea, Labiatae, Borragineae, Liliaceae, Irideae, Amaryllideae, etc. In addition to'these, there are many other hardy species, representing at least fifty more natural orders. Herbaceous plants are either monocarpic or polycarpic (fruiting only once, or fruiting more than once). But the more familiar classification of herbs, according to their duration, is better suited for practical purposes. Perennial plants with few exceptions are polycarpic, and biennials and annuals are naturally monocarpic; some perennials, especially tender ones, that will flower the same season from seed, are treated as annuals; and some annual plants may be preserved in the absence of seed by propagating them from cuttings. But at best this is a very unsatisfactory procedure, except where the loss of a valuable species or variety depends upon the life of a single individual. In the following arrangement of herbaceous vegetation, we have preferred references to orders and genera in many instances instead of giving detailed lists of species, as it will be necessary to turn to the descriptive portion for information respecting height, colour, etc.