This section is from the book "The Gardener V2", 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.
In foliage, style of growth, and general appearance they are suggestive of the Cypresses, to which family, though separated by some peculiar botanical characters, they have evidently a close affinity.
Though little more than twenty years have passed away since the first representative of the group was introduced into European collections, there are already some eighteen or twenty species and varieties in cultivation more or less distinct, but without exception eminently handsome; and even from the short experience we have had of them in this country, the great majority having been sent home since 1864, there is no doubt of their adaptability to our soils and climate, and that they are invaluable acquisitions as decorative shrubs.
In habits of growth they are for the most part dwarf and bushy, in some cases only rising a few feet from the ground, and are thus most useful for planting in miniature gardens, grouping in flower-garden beds, or for rockeries. Two of the species, however, attain the dimensions of trees, producing timber of such excellent quality, both as regards its durability and fineness of grain, that it is much used by the Japanese cabinet-makers for their most artistic work.
Like many of their congeners, the Retinosporas thrive best in a deep rich loamy soil, with the land sufficiently drained to prevent any accumulation of water at the roots; and though they are for the most part hardy enough to withstand any amount of frost they are likely to be subjected to in this country, they require a sheltered situation, or at least one where they are not exposed to the full force of violent winds.
While each of the various sorts, whether species or varieties, has its own peculiar claims upon the attention of planters of ornamental shrubs, and may with confidence be recommended as worthy of introduction among the most choice of that class of plants, where space and other circumstances permit, we note the following as specially distinct and attractive: -
This is a pretty dwarf species, rarely found in its native habitats higher than from 4 to 6 feet. It is much valued as an ornamental plant by the Japanese, who use it in the decoration of their gardens, and as a pot-plant for balconies and terraces.
It is here a slow-growing conical bush, clothed to the ground with innumerable tiny heath-like branches, densely covered with small leaves of a glaucous-green colour in summer, changing on the approach of winter to a bright violet-purple. It is a fine rockery plant, and most useful for winter bedding, or for margins of ornamental shrubberies, where it makes a striking contrast with others of a light-green hue.
It prefers a dry, airy, but sheltered situation, and a good rich soil, and in order to allow it to develop its true character, should always be allowed sufficient space to be free from contact with the other plants.
Like the preceding, this is a dwarf species, very hardy in this country, and forms a singularly elegant bushy shrub, with abundance of small branches divided into flat, frond-like branchlets. The foliage is small, but thickly set on the stems, and has a rich, bright-green colour, which it retains all over the year. It is altogether a most distinct and desirable plant, well suited for a rockery, or indeed any situation where a miniature, slow-growing evergreen is required.
Retinospora Leptoclada (The Fiat Branchletted Retinospora) is another dwarf form never found in its native valleys higher than from 4 to 6 feet. It is a favourite pot-plant with the Japanese, and as such is met with very frequently in the gardens of Yeddo. In this country it is an exquisitely pretty plant of a sharply conical shape, the branches very dense, and divided into numerous short flattened branchlets, each one resembling the fronds of a Pern or Lycopod. The foliage has a distinct silvery-grey colour, assuming a darker hue in winter. It is a superb winter garden or rockery plant, and ought to be extensively grown, both for its neat form and its distinct colour.
Retinospora lycopodioides (the Club-Moss Retinospora), also a dwarf species, with a spreading rather than a conical habit of growth, the branches very abundant, and divided into slender branchlets, densely clothed with leaves imbricated round the stem. The colour is bright green - equally so in winter as in summer. It is an elegant and distinct-looking plant, well worthy of cultivation, and suitable for similar purposes as the other dwarf species, and like them of slow growth.
This magnificent species is found in various districts in Japan, particularly on the Island of Niphon, where it is the principal forest-tree, and rises to heights of from 70 to 100 feet, with a straight arrow-like stem from 3 to 5 feet in diameter at the base. Its timber is fine-grained, capable of receiving a brilliant polish, and of a beautiful white colour - qualities so much appreciated by the Japanese, that they regard it as sacred, call it the "Tree of the Sun," and use it in the construction of their temples and other religious buildings.
Though as yet a comparative stranger to British gardens, it is already widely distributed; and enough has been seen of it to prove that it is a most valuable lawn specimen-plant, of free growth, and thoroughly hardy, thriving in almost every district of the country and in every variety of soil, and an acquisition equal in importance to any of the grand introductions of a similar kind from California.
In a young state its habit of growth is sharply conical, but as it advances the branches become more spreading, and show a tendency to assume the broad horizontal style characteristic of the tree on its native mountains. The foliage is of a rich dark-green colour, and the general appearance similar to that of the Cypresses.
Like all the rest of its tribe, it grows best when sheltered and in good rich soil, and is never more beautiful than when planted singly as a specimen on grass.
Among several varieties there are two variegations deserving of special notice - the one, named aurea, has its green branchlets freely intermixed with golden yellow, and argentea, in a similar manner with silvery white. Both were found originally in gardens in Japan, as indeed were most, if not all, the varieties in cultivation. These are much dwarfer than the species, but quite as hardy, and very effective in spring when making their young growths.
Retinospora pisifera (the pea-fruited Retinospora), found wild in mountain forests in the Island of Niphon associated with Retinospora obtusa, is a very handsome but much smaller tree, seldom rising higher than from 20 to 30 feet, and producing timber of equal value to that species.
It is here thoroughly hardy, and grows more rapidly than Retinospora obtusa, forming a beautiful lawn-specimen of a broadly conical shape; the branches very slender, and shooting out from the stem in a horizontal direction. The foliage has a distinct, warm, green tint on the upper surface, and is bright glaucous on the under. It thrives well under similar conditions with Retinospora obtusa, to which it is a fine companion-plant.
The following varieties can scarcely be too highly spoken of - their neat style of growth and brilliancy of colours render them almost universal favourites, and must always secure for them a prominent place among decorative shrubs; they are dwarfer than the species, but quite as hardy, and invaluable for flower-garden beds or rockeries: Argentea, with most of its branchlets tipped with bright silvery white; Aurea, and Nana aurea, the latter one of the dwarfest and neatest of Conifers, the branchlets of both appearing as if gilt with the purest gold.
Retinospora Squarrosa (The Scaly-Leaved Retinosjpora) is found wild on the Island of Kiusiu in Japan, where it attains a height of from 10 to 15 feet. It is only seen here as a small round-headed bush, densely furnished with long slender branches, clothed with abundance of glaucous-coloured leaves. It is quite hardy, but requires a sheltered situation, and is handsome enough to be recommended as a rock-work plant, or for associating with the other dwarf species in flower-garden beds, to which, from its peculiar colour, it makes an effective contrast.
This is a very distinct and interesting species, among the most recently introduced of the genus. The experience of the last three or four winters proves its perfect hardiness; while it is found to grow in ordinary soils quite as freely as the other species. In habit of growth it is very compact, with a blunt round top; the branches are slender individually, but produced in great abundance • the foliage has a light-green or slightly glaucous tint.
It is a superb dwarf shrub, not likely to rise higher that 2 or 3 feet from ^the ground, and admirably suited for arrangements of neat dwarf plants.
A charming variegated variety, P. aurea, has a fine golden tint intermixed with its green spray, and is also a fine dwarf plant, very effective, particularly in early spring and summer.