Rose (Botany) - Encyclopedia

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ROSE (Rosa). The rose has for all ages been the favourite flower, and as such it has a place in general literature that no other plant can rival. In most cases the rose of the poets and the rose of the botanist are one and the same in kind, but popular usage has attached the name rose to a variety of plants whose kinship to the true plant no botanist would for a moment admit. In this place we shall employ the word in its strict botanical significance, and in commenting on it treat it solely from the botanical point of view. The rose gives its name to the order Rosaceae, of which it may be considered the type. The genus consists of species varying in number, according to the diverse opinions of botanists of opposite schools, from thirty to one hundred and eighty, or even two hundred and fifty, exclusive of the many hundreds of mere garden varieties. While the lowest estimate is doubtless too low, the highest is enormously too large, but in any case the wide discrepancies above alluded to illustrate very forcibly the extreme variability of the plants, their adaptability to various conditions, and consequently their wide dispersion over the globe, the facility with which they are cultivated, and the readiness with which new varieties are continually being produced in gardens by the art of the hybridizer or the careful selection of the raiser. The species are natives of all parts of the northern hemisphere, but are scantily represented in the tropics unless at considerable elevations.

They are erect or climbing shrubs, never herbs or trees, generally more or less copiously provided with straight or hooked prickles of various shapes and with glandular hairs, as in the sweet-brier or in the moss-rose of gardens. The prickles serve the purpose of enabling 'the shrub to sustain itself amid other vegetation. The viscid hairs which are specially frequent on the flower stalks or in the neighbourhood of the flower serve to arrest the progress of undesirable visitants, while the perfume emitted by the glands in question may co-operate with the fragrance and colour of the flower to attract those insects whose presence is desirable. The leaves are invariably alternate, provided with stipules, and unequally pinnate, the leaflets varying in number from one (as in R. simplicifolia or berberi folia) to 11 and even 15, the odd leaflet always being at the apex, the others in pairs. The flowers are solitary or in loose cymes (cluster-roses) produced on the ends of the shoots. The flower-stalk expands into a vaseor urn-shaped dilatation, called the receptacle or receptacular tube, which ultimately becomes fleshy and encloses in its cavity the numerous carpels or fruits. From the edge of the urn or "hip" proceed five sepals, often more or less compound like the leaves and overlapping in the bud. Within the sepals are five petals, generally broad or roundish in outline, with a very short stalk or none at all, and of very various shades of white, yellow or red. The very numerous stamens originate slightly above the sepals and petals; each has a slender filament and a small two-celled anther. The inner portion of the receptacular tube whence the stamens spring is thick and fleshy, and is occasionally spoken of as the "disk"; but, as in this case it does not represent any separate organ, it is better to avoid the use of the term. The carpels are very numerous, ultimately hard in texture, covered with hairs, and each provided with a long style and button-like stigma. The carpels are concealed within the receptacular tube and only the stigmas as a rule protrude from its mouth. Each carpel contains one ovule. The so-called fruit is merely the receptacular tube, which, as previously mentioned, becomes fleshy and brightly coloured as an attraction to birds, which devour the hips and thus secure the dispersion of the seed. The dry one-seeded fruits (achenes) are densely packed inside the hip, and are covered with stiff hairs which cling to the bird's beak. The stamens are in whorls, and, according to Payer, they originate in pairs one on each side of the base of each petal so that there are ten in each row; a second row of ten alternates with the first, a third with the second, and so on. By repeated radial and tangential branching a vast number of stamens are ultimately produced, and when these stamens assume a petaloid aspect we have as a consequence the double flowers which are so much admired. The carpels are much less subject to this petaloid change, and, as it generally happens in the most double of roses that some few at least of the anthers are formed with pollen, the production of seed and the possibility of cross-breeding become intelligible. Under natural circumstances rose flowers do not secrete honey, the attraction for insects being provided by the colour and perfume and the abundance of pollen for food. The stigmas and anthers come to maturity at the same time, and thus, while cross-fertilization by insect agency is doubtless most common, self-fertilization is not prevented.

The large number of species, subspecies, varieties and forms described as British may be included under about a dozen species. Among them may be mentioned R. spinosissima, the Scotch rose, much less variable than the others; R. rubiginosa (or R. eglanteria), the sweet-brier, represented by several varieties; R. canina, the dog rose (see fig.), including Dog Rose (Rosa canina) in flower and fruit (half natural size).

numerous subspecies and varieties; the large-fruited apple rose, R. pomifera; and R. arvensis, the parent of the Ayrshire roses. Cultivated roses are frequently "budded" or worked upon the stems of the brier or R. canina, or upon young seedling plants of the same species; and upon stems of an Italian rose called the Manetti, raised in the Milan Botanic Gardens about 1837. Other species, notably R. polyantha, also are used for stocks.

Roses have been grown for so many centuries and have been crossed and recrossed so often that it is difficult to refer the cultivated forms to their wild prototypes. The older roses doubtless originated from R. gallica, a native of central and southern Europe. R. centifolia (the cabbage rose), a native of the Caucasus, contributed its share. A cross between the two species named may have been the source whence originated the Bourbon roses. The yellow-flowered Austrian and Persian brier originated from R. lutea, a native of Austria and the East. The monthly or China roses sprang from the Chinese R. indica, and these, crossed with others of the R. centifolia or gallica type, are the source of the "hybrid perpetuals" so commonly grown nowadays, because, in addition to their other attractions, their blooming season is relatively prolonged, and, moreover, is repeated in the autumn. Tea roses and noisettes, it is to be presumed, also acknowledge R. indica as one of their progenitors. A magnificent race called "hybrid teas" have been evolved of late years, by crossing the tea roses and hybrid perpetuals. They are much more vigorous in constitution than the true tea roses, while quite as beautiful in blossom and more perpetual in bloom than the hybrid perpetuals. Recently, by crossing the Japanese R. Wichuraiana with hybrid perpetuals, a beautiful and vigorous race of climbers has been produced. The Banksian rose is a Chinese climbing species, with small white or fawn-coloured flowers of great beauty, but rarely seen; the Macartney rose (R. bracteata) is also of Chinese origin. Its nearly evergreen deep green leaves and large white flowers are very striking. The Japanese R. rugosa is also a remarkable species, notable for its bold rugose foliage, its large white or pink flowers, and its conspicuous globular fruit.

R. damascena is cultivated in some parts of the Balkans for the purpose of making attar of roses. In Germany the same variety of rose is used, while at Grasse a strain of the Provence rose is cultivated for the same purpose. In India R. damascena is grown largely near Ghazipur for the purpose of procuring attar of roses and rose water.

Rose water is chiefly produced in Europe from the Provence or cabbage rose, R. centifolia, grown for the purpose at Mitcham and much more abundantly in the south of France. Conserve of roses and infusion of roses, two medicinal preparations retained for their agreeable qualities rather than for any special virtue, are prepared from the petals of R. gallica, one variety of which was formerly grown for the purpose near the town of Provins. Conserve of dog rose is made from the ripe hips of the dog rose, R. canina. Its only use is in the manufacture of pills.

The rose is so universal a favourite that some portion of the garden must necessarily be devoted to it, if the situation be at all favourable. Many choice roses will not, however, thrive in the vicinity of large towns, since they require a pure air, and do not endure a smoky atmosphere. The best soil for them is a deep rich strong loam free from stagnant moisture. Very light sandy or gravelly soils, or soils which are clayey and badly drained, are not suitable, and both must be greatly improved if rose-growing on them is attempted. Light soils would be improved by a dressing of strong loam in conjunction with cow-dung or nightsoil; the latter, provided it is properly prepared and not too fresh, is indeed the very best manure for roses in all but soils which are naturally very rich. Heavy soils are improved by adding burned earth or gritty refuse, with stable manure and leaf-mould, peat moss litter, &c.; and damp soils must necessarily be drained by trenching. Tea roses may, however, be grown to perfection in a gravel soil, provided it be well manured, cow manure being best. Roses generally require a constant annual supply of manure, and, if this is given as a mulching in autumn, it serves to protect their roots through the winter. They also require liberal supplies of water during the growing season, unless the surface is mulched or top-dressed from time to time with well-rotted manure. Aphides and caterpillars of all kinds may be checked by syringing with dilute tobacco water or some of the many insecticides now provided to facilitate this rather troublesome task.

Some growers prefer roses grown on their own roots, some on the Manetti and others on the brier stock. There is this to be said in favour of their own roots that, if the tops are killed down by accident or by severe weather, the roots will usually throw up new shoots true to their kind, which cannot be looked for if they are worked; though it is sometimes recommended to plant deep in order that the rose itself may learn to do without its foster parent the stock. Too often, however, in the case of persons unfamiliar with roses, the choice rose dies, and the stock usurps its place. This is especially true of the Manetti stock, as its foliage is more like that of many cultivated forms than the brier, and therefore more easily overlooked. Where standards or half-standards are required, the brier stock from the hedges is always used. It forms the most reliable stock for dwarfs of all kinds, and especially for tea roses, most of which fail on the Manetti stock.

An open situation, not shaded but sheltered from strong winds, is what the rose prefers. October and November are the best months for planting roses, but if the weather be wet or frosty and the soil sticky, the plants should be placed in a sheltered place and protected by green boughs or matting until suitable conditions prevail. The planting should never be deep, the uppermost layer of roots being about 2 or 3 in. below the general level of the surface, and the soil should always be kept stirred with the hoe during the summer months. In regard to pruning, roses vary considerably, some requiring close cutting and others only thinning out; some again, such as strong growing climbers, may be safely pruned in autumn, and others are better left till spring. Instructions on this point as to the several groups of varieties will be found in most rose catalogues, and may be followed, provided the variety is true to name. It may be laid down as a general rule that the more strongly growing varieties should be less severely cut back than the weakly varieties; and, again, the more tender the variety, the later in the spring should the pruning be done, April being the best month for pruning teas and noisettes. It should be remembered also that no amount of correct pruning will improve a rose bush that has been badly planted or placed in a quite unsuitable position.

Where dwarf beds of roses are required, a good plan is to peg down to within about 6 in. from the ground the strong one-yearold shoots from the root. In due time blooming shoots break out from nearly every eye, and masses of flowers are secured, while strong young shoots are thrown up from the centre, the plant being on its own roots. Before winter sets in, the old shoots which have thus flowered and exhausted themselves are cut away, and three or four or more of the strongest and best ripened young shoots are reserved for pegging down the following season, which should be done about February. In the meantime, after the pruning has been effected, plenty of good manure should have been dug in lightly about the roots. Thus treated, the plants never fail to produce plenty of strong wood for pegging down each succeeding season.

The most troublesome fungoid pest of the rose is undoubtedly the mildew (Sphaerotheca pannosa). The young shoots, leaves and flower-buds frequently become covered with a delicate white mycelium, which by means of the suckers it sends into the underlying cells robs its host of considerable amounts of food, and causes the leaves to curl and fall early. The spores are produced in great abundance and carried by animals and the wind to other plants, and so the disease is rapidly spread. Later the mycelium increases and forms a thick velvety coating on the young shoots, and in this the winter state of the fungus is produced. Spraying with potassium sulphide (1 oz. to 2 to 3 gallons of water) is the best means of checking the spread of the disease. The rose rust (Phragmidium subcorticatum) appears on both cultivated and wild roses in the spring, bursting through the bark in the form of copious masses of orange powder consisting of the spores of the fungus. These spores infect the leaves, and produce on them in the summer small dots of an orange colour and, later, groups of spores that are able to live through the winter. The last, the teleutospores, are of a dark colour, and it is by these that the disease is started in the spring. It is therefore important that all the affected leaves should be destroyed in the autumn, and the bushes should be sprayed with Bordeaux mixture or ammoniacal copper carbonate in the spring to prevent the infection of the leaves by spores brought from a distance. Many other fungi attack the rose, but perhaps the only other one that merits mention here is Actinonema Rosae. This attacks the leaves, forming large dark blotches upon them and frequently causing them to fall prematurely.

A very large number of insect pests are found upon the rose, but the best known and most formidable on account of their great powers of reproduction are the aphides. More than one species is found upon the rose, though Aphis Rosae is the commonest. Their attack should be checked by the use of a spray made by boiling 4 oz. quassia chips for an hour or so in a gallon of soft water, straining off the solution and dissolving therein 4 oz. of soft soap while it is still warm, afterwards adding I or 2 gallons of soft water according to the age of the rose leaves that are to be sprayed. Any delay in dealing with the pest gives the opportunity for its increase, even a day being sufficient materially to augment their numbers. The larvae of some of the Tortrix moths fold the leaves almost as soon as they are developed from the bud, and do considerable damage in this way and by devouring the leaves, while several "looper" caterpillars are also found feeding on the foliage. Many species of saw-fly larvae are also known to attack the rose, feeding either upon the leaves or devouring the young shoot. These larvae should be carefully searched for and destroyed whenever found. One of the leaf-cutting bees, Megachile, cuts pieces out of the leaves with which to line its nest, materially reducing their effective surface. The bees may be caught in a butterfly net or traced to their nests, which should be destroyed.

For further information see the late Dean Hole's Book about Roses (1894); Book of the Rose, by Rev. A. Foster Mellias (1905); Beautiful Roses for Garden and Greenhouse, by J. Weathers (1903); and Roses, their History, Development and Cultivation, by the Rev. J. H. Pemberton (1908).

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