This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
There is a very numerous class of hardy perennials with evergreen foliage which may be used in the flower-garden with good effect in summer in conjunction with the usual classes of summer bedding-plants. A more general introduction of the hardy perennial classes of plants with evergreen or persistent leaves with the varied tones of green, grey, white, yellow, and bronze, which they offer at all seasons of the year, would, I think, be a step in the right direction in many cases. Individually, even in pots or in small patches, many of the species which I allude to, and which I will particularise more fully further on, are very attractive at all times; but in masses of some breadth, or broad lines or bands, they would be still more so. Much of the difficulty that is experienced in mitigating the evils of empty beds and borders in winter would be done away with if suitable hardy plants could be found that may be adapted to the style of bedding-out that finds most favour with the flower-gardening public at present. I think there is no difficulty as to the plants - they are plentiful, and may easily be obtained by the thousand if the demand is raised, as the various kinds that are suitable may be increased by the simplest means ad libitum.
Not a few of the class to which I invite attention in this paper are already employed in the parterre in summer in various ways. Carpet-bedding has drawn a few of the more suitable forms of Semper-vivums, Saxifragas, and a few other hardy perennials into service with excellent effect in that style of garden decoration. In geometrical designs two hardy plants of similarly adaptable habit of growth are successfully introduced, with perfect harmony alike with the design and the gayer classes of plants more commonly employed for the summer furnishing of the flower-garden. An old familiar plant, such as Pennyroyal (Mentha pulegium), only requires to appear with its leaves tinted golden instead of green; or the pretty but weedy Stitchwort (Stellaria) to assume the same hue instead of its pale grassy green, to become the pet plants of the period with flower-gardeners. Neither of these is in the category which I am considering. They are not evergreen, or rather ever-yellow, to such a degree as to render them commendable for the purpose of clothing the bare surface of the earth in winter; but being familiar plants to flower-gardeners, their habit of growth will serve to illustrate a considerable number of the species and varieties of hardy plants which I should like to see more generally employed in the way spoken of.
There cannot be any objection to the introduction of plants of similar habit to these, if only they can be proved to have colour sufficiently distinct and pronounced to aid in producing a contrast or pitching a harmony with something else. Well, the proof will be more or less difficult just according to the depth of the prejudices of those who address themselves to the weighing of it. But those who are in earnest about the improvement of flower-gardening, and about getting the largest amount of pleasure at all seasons of the year from the flower-garden as a result of their efforts and outlay, will have few prejudices to overcome: they will test and try and judge all subjects that may be brought before them on their merits. This is exactly what I should wish to see done with many of the plants which I shall name and briefly describe before I close this paper.
The styles of flower-gardens to which I consider the class of plants in view best adapted are terrace-gardens, where either box or stone edgings are used, or panelled ones, in which the design is viewed from a greater or less elevation, and which are based in gravel-walks or deficient in surrounding masses of green. Being all plants of a neat compact habit of growth, which will be improved by the close attention, in keeping to which they would be subjected in the flower-garden, they are capable of being worked into any design, no matter how intricate. The perfection of the summer keeping would tend to enhance their beauty in winter. It is only when they are allowed to degenerate into untidy condition that many of the neatest and prettiest of the evergreen alpine and other dwarf-growing evergreen perennials become unattractive in any position in which they may be placed, and this untidiness leads to their becoming patchy and rusty in winter.
I will now proceed to give a list, with slight descriptions of the species which are best adapted to the object in view. The list will be more suggestive than exhaustive, the aim being to present a few of the best only.