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MANY OF the ever-blooming roses cannot, in our climate, be cultivated in the open air without extreme precaution to protect them from the cold. To grow them most successfully, the aid of glass is necessary. Many of the Hardy Perpetual roses may also be grown with advantage in pots, by which means their bloom may be prolonged into the early winter months, or they may be forced into premature flowering long before their natural season of bloom. The first essential in the pot culture of roses is the preparation of the soil. Those of delicate growth, like most of the China and Tea roses, require a lighter soil than the more robust varieties, like most of the Hardy Perpetuals. A mixture of loam, manure, leaf-mould, and sand, in the proportion of two bushels of loam to one bushel of manure, one bushel of leaf-mould, and half a bushel of sand, makes a good soil for the more delicate roses. For the more robust kinds, the proportion of loam and of manure should be greater. In all cases, the materials should be mixed two or three months before they are wanted for use, and turned over several times to incorporate them thoroughly. They are frequently, however, mixed, and used at once. The best loam is that composed of thoroughly rotted turf. A very skilful English rose-grower, Mr. Rivers, recommends the compact turf shaved from the surface of an old pasture, and roasted and partially charred on a sheet of iron over a moderate fire. I have found no enriching material so good as the sweepings from the floor of a horse-shoer, in which manure is mixed with the shavings of hoofs. It is light and porous, and furnishes, in decomposing, a great quantity of ammonia. For the more delicate roses it is particularly suited, while the stronger kinds will bear manures of a stronger and denser nature. The light black soil from the woods is an excellent substitute for leaf-mould; or, to speak more correctly, it is a natural leaf-mould in the most thorough state of decomposition.
Young and thrifty roses which have been grown during summer may be potted for the house in September. They should be taken up with care, the large straggling roots cut back, and all bruised ends removed with a sharp knife. The ends of the branches should also be cut back. They may then be potted in the compost just described, which should first be sifted through a very coarse sieve. The pots must be well drained with broken crocks placed over the hole at the bottom. Care must be taken that the pot be not too large, as this is very injurious. A sharp stick may be used to compact the soil about the roots; and from half an inch to an inch in depth should be left empty at the top, to assist in thorough watering, which is a point of the first importance.
When the roses are potted, they should be placed in a light cellar or shed, or under a shady wall. They must be well watered, and it is well to syringe them occasionally. In a week or two they will have become established, and may then be removed to a greenhouse without fire, and with plenty of air; care, however, being taken to protect them from frost at night.
The roses so treated are intended for blooming from mid-winter to the end of spring; and we shall soon speak further of them under the head of Forcing.
A great desideratum is the obtaining of roses in the early part of winter. This may be done by growing everblooming roses in pots in the open air during summer, plunging the pot in the earth, and placing a tile or brick beneath it to prevent the egress of roots and the ingress of worms. Towards the end of August, cut off all the flowers and buds, at the same time shortening the flower-stalks to two or three eyes. Then give the roses a supply of manure-water to stimulate their growth. If they are in a thrifty condition, they will form new shoots and flower-buds before the frost sets in; and may then be removed to a cold greenhouse, where they will continue, to flower for several months.
The following is the description given by Mr. Rivers of a practice recently introduced in England, and which seems well worth a trial here, with such modifications as the heat of our sun may require:—
"To have a fine bloom of these roses, or, indeed, of any of the Hybrid Perpetuals, Bourbons, or China roses, in pots towards the end of summer or autumn, take plants from small pots (those struck from cuttings in March or April will do), and put them into six-inch, or even eight-inch pots, using a compost of light turfy loam and rotten manure, equal parts: to a bushel of the compost add half a peck of pounded charcoal, and the same quantity of silver sand; make a hot-bed of sufficient strength, say three to four feet in height, of seasoned dung, so that it is not of a burning heat, in a sunny, exposed situation,' and on this place the pots; then fill up all interstices with sawdust, placing it so as to cover the rims, and to lie on the surface of the mould in the pots about two inches deep. The pots should have a good sound watering before they are thus plunged, and have water daily in dry weather. The bottom heat and full exposure to the sun and air will give the plants a vigor almost beyond belief. This very simple mode of culture is as yet almost unknown. I have circulated among a few friends the above directions; and have no doubt, that, in the hands of skilful gardeners, some extraordinary results may be looked for in the production of specimens of soft-wooded plants. I may add, that, when the heat of the bed declines towards the middle of July, the pots must be removed, some fresh dung added, and the bed remade, again plunging the plants immediately. Towards the end of August, the roots of the plants must be ripened: the pots must, therefore, be gradually lifted out of the saw-dust; i.e., for five or six days, expose them about two inches below their rims; then, after the same lapse of time, a little lower, till the whole of the pot is exposed to the sun and air: they may be then removed to the greenhouse, so as to be sheltered from heavy rain. They will bloom well in the autumn, and be in fine order for early forcing. If plants are required during the summer for exhibition, or any other purpose, care must always be taken to harden or ripen their roots, as above, before they are removed from the hot-bed."