With the aid of these pots, sea-cale is now forced in a very simple way, in the open border. In the latter end of the autumn, a bed of vigorous sea-cale is dressed off, that is, the stalks are cut over, and all decayed leaves are removed. The ground is at the same time stirred or loosened around the plants, and a thin stratum of fine gravel or of sifted coal ashes is laid on the surface, in order to keep down earth-worms. A pot with a moveable cover is placed over each plant, or over each patch of plants, if two or more have remained together. Stable litter is then closely packed all around the pots, and pressed firmly down ; and successive quantities are added, till the pots be buried to the depth of a foot or more ; the whole thus assuming the form and ap pearance of a large hot-bed. When fermentation commences, a thermometer should occasionally be introduced into a few of the pots, in order to ascer tain the temperature within, which should never ex ceed 60° Fahr. The depth of the covering of litter, therefore, is to be increased or diminished, accord ing to the state of the fermentation, and partly ac cording to the severity of the season. The vegeta tion of the included plants is speedily promoted ; so that, in the space of a month, the most forward shoots will probably be ready for cutting. The shoots thus produced, being completely excluded from the action of light, are most effectually etio lated, and exceedingly tender and crisp. The ad vantage of the moveable lids must now be evident : the state of the plants or stools can be examined, and such shoots as are ready can be gathered, with out materially disturbing the litter or dissipating the heat. This simple mode of forcing sea-cale has every where superseded the practice of planting it on hot-beds under glass-frames, formerly recom mended by Abercromby and other writers on horti culture. This vegetable, it may be remarked, in one respect forms an exception to all others : it is of better quality, when forced in the midst of winter, than when produced naturally in the spring season.
By the modes of culture which have now been described, sea-cale shoots can readily be furnished fresh for the table, from the middle of November till the middle of May.
Rhubarb Stalks.
These are now so much in demand for the mak ing of tarts, that they have become a leading article of trade with the green grocers of London and Edin burgh. The practice of using them seems peculiar to this country ; at least it is unknown to the French, the Dutch, or the Germans. The stalks at present sent to market are evidently of finer quality than in former years. By the mode of culture practised, especially the employment of young seedling plants only, the frequent removal of the leaves, and pre venting the plant from flowering, the leaf-stalks are rendered more tender than those of plants which have been long established in a garden. Indeed, some of the varieties which have been raised from seed, especially by Messrs Peacock of Edinburgh, have leaf-stalks of a more succulent nature than usual. These appear to be intermediate varieties ;
and have been raised from seeds yielded by plants of Rheum rhaponticum, growing close by R. hybri dam, compactum, and Sibiricum,—the leaf-stalks of which species are used indiscriminately. Such suc culent stalks, when peeled, cut down and baked into tarts, have all the appearance of apples, and are by many people preferred to them. In the open ground the stalks are produced from April till midsummer. The progress of vegetation may be hastened during the month of March, by throwing over the plants some loose haulm, care being taken not to injure the shoots, which at that season are very brittle.
Rhubarb may be forced, much in the manner above described for sea-cale ; and the leaf-stalks are thus not only rendered tender, but, being at the same time blanched, become of a fine light colour, and have less of the peculiar flavour of the plant, which is an advantage. The smaller species, such as R. crispum and undulatum, are best for this pur pose, being most easily confined within the covers. In the third volume of the Transactions of the Lon don Horticultural Society, a mode of forcing the rows of rhubarb, by means of an open frame of wood-work, surrounded with stable litter, is de scribed. Stakes between three and four feet long are driven into the ground opposite to each other, on each side of the row of plants, making the in cluded bed or row two feet wide. The stakes are contracted at top, or made to slope inwards, by means of connecting cross pieces, fifteen inches long. Two or three lath-spars are nailed horizon tally along the side stakes, in order to keep the lit ter from falling in upon the plants. The lining of dung should not be less than eighteen inches thick ; the longest litter should be reserved for the top, so as to be easily removed when the state of the in terior is to be examined. This plan is well adapt ed for forcing and blanching the larger species of rhubarb, which could not be confined within sea cale covers.
Mr Knight (who gives his attention equally to humble details of practical utility, and to philo sophical speculations connected with horticulture, and whose name will often fall to be mentioned in this article) has described a method of for cing rhubarb by planting in pots. In the begin ning of winter a number of roots of rhubarb are slug up, and placed in Some large and deep pots, each pot being made to receive as many as it will contain. Some fine sandy loam is then washed in, so as closely to fill the interstices between the roots, the tops or which are so placed as to be level with each other, and about an inch below the surface of the mould in the pots. The pots are placed in any kind of hot-house ; and other pots of the same size are inverted over them. If water be freely sup plied, vegetation proceeds very rapidly : three suc cessive crops of leaf-stalks may generally be ob tained. The shaded spaces of vineries or peach houses, which are generally wholly unoccupied, are exceedingly well suited for forcing rhubarb in this mariner.