CHAPTER XV.

OF POTTING.

WHEN a plant is forced to grow in a small earthen vessel like a garden pot, its condition is exceedingly different from that to which it would be naturally exposed. The roots, instead of having the power of spreading constantly outwards, and away from their original starting point, are constrained to grow back upon themselves; the supply of food is comparatively uncertain; and they are usually exposed to fluctuations of temperature and moisture unknown in a natural condition. For these reasons, potted plants are often in worse health than those growing freely in the ground; but, as the operation of potting is one of indispensable necessity, it is for the scientific gardener, firstly, to guard against the injuries sustainable by plants to which the operation must be applied; and, secondly, to avoid, as far as may be possible, exposing them to such an artificial state of existence. That the latter may be done more frequently than is supposed will be sufficiently obvious, when we have considered what the purposes really are that the gardener needs to gain by potting.

The first and greatest end attained by potting is, the power of moving plants about from place to place without injury; greenhouse plants from the open air to the house, and vice versá; hardy species, difficult to transplant, to their final stations in the open ground without disturbing their roots; annuals raised in heat to the open borders; and so on: and, when this power of moving plants is wanted, pots afford the only means of doing so. It also cramps the roots, diminishes the tendency to form leaves, and increases the disposition to

432

CONSTRUCTION OF GARDEN-POTS.

flower. Another object is, to effect a secure and constant drainage from roots of water; a third is, to expose the roots to the most favourable amount of bottom-heat, which cannot be readily accomplished when plants of large size are made to grow in the ground even of a hothouse; and, finally, it is a convenient process for the nourishment of delicate seedlings. Unless some one of these ends is to be answered, and cannot be effected in a more natural manner, potting is better dispensed with.

Many suggestions have been made with a view to improve the construction of the common garden-pot. The following deserve to be recorded. One is a contrivance by Mr. Fry, of Blackheath, for examining the roots of plants in very large pots. It is not possible to take the "ball" out of such pots by the usual process of inverting them, and allowing the ball to drop, because they are too heavy. Mr. Fry meets the difficulty by the following contrivance. A pot is made with a moveable bottom, concave on the upper side like a saucer. When the ball of such a pot is to be examined, the latter is placed upon a heavy wooden block cut into a cylindrical form, which forces upwards the moveable bottom, and carries the ball with it without the slightest disturbance. After the roots have been examined, the pot is lifted upwards till the ball is replaced, and the wooden cylinder is removed. Mr. Beaton proposes to do away with the hole at the bottom altogether; and, instead of the flat bottom, the maker elevates the centre of it, like the bottom of a common black bottle; drainage-holes being round the sides at the bottom. to the size of the pot, are sufficient. the bottom, neither can the worms get in, and water cannot hang under the pot in winter." Another proposal is, that when plants are intended for bedding out, they should first be put into pots having both ends open, and that the seeds should be sown on the broad end, which is kept uppermost.

From two to six holes, according "The roots cannot get through

That potting may be dispensed with in many cases, is evident from several facts more or less well known. The nurserymen prefer "pricking out" their delicate seedlings into pans, or moveable borders, instead of pots; and they always thrive the better. In conservatories, the necessity of shifting plants from place to place may be often avoided; while, under judicious management, those which are planted in the open soil have greatly the advantage of others, both in healthiness and easiness of management; and it is found that Pine-apples

SOIL IN POTS SOON EXHAUSTED.

433

succeed better unpotted, if planted freely in soil exposed to a proper amount of bottom-heat. This was first asserted by Mr. Martin Call, one of the Emperor's gardeners at St. Petersburg (Hort. Trans., iv. 471), and has been since practised very successfully by others. In the year 1830, a Pine-apple, obtained by this treatment, weighing 9 lb. 4 oz., was sent to the King of England by Mr. Edwards, of Rheola; and in modern practice all great Pine growers adopt this plan when circumstances permit them to do so. (See A Treatise on the Hamiltonian System of Cultivating the Pine Apple. By Joseph Hamilton. Ed. 2, London, 1845.)

The exhaustion of soil by a plant is one of the most obvious inconveniences of potting. The nutrient matter in a soluble state, contained in a garden pot, must necessarily be soon consumed by the numerous roots crowded into a narrow compass and continually feeding upon it. The effects of this are seen in the smallness of leaves, the weakness of branches, the fewness and imperfect condition of flowers, &c.; and the gardener remedies them by applying liquid manure, by frequent shifting, or by placing his plants in pan-feeders, shallow earthen vessels containing manure, to which the roots have access through the holes in the bottom of a pot. It is, however, to shifting more particularly, that recourse is had for renovating the soil; and this, if skilfully performed, without giving a sudden and violent shock to the plant, is probably the best means; because the roots are thus allowed more liberty of distribution, and the earth is kept more permeable than when consolidated by repeated applications of liquid manure. There is, however, a difficulty in shifting plants without injury to their roots, in the midst of full vegetation; and at such times the application of liquid manure is preferable when the soil requires renovation.

Every one knows that the soil of a farm will not bear, year after year, the same kind of crop, but that one kind of produce is cultivated on a piece of ground one year, and is succeeded by some other kind; which practice, in part, constitutes the important system of rotation of crops. Not, however, to refer to matters extra-horticultural, it is notorious that an Apple orchard will not immediately succeed upon the site of an old

FF

orchard of the same kind of fruit; a wall-border, in which fruit-trees have been long grown, becomes at last insensible to manure, and requires to be renewed; and, not to dwell upon an undisputed fact, Dahlias do not "like" the soil in which Dahlias were grown the previous year. What is the real cause of this? Not exhaustion of ordinary fertilising ingredients, because that exhaustion is made good and yet to no purpose. Are we to assume, what seems to be the fact, that land contains something mineral which each species prefers to feed on, and which is not contained in ordinary manure? This will be further considered in the final chapter on soil and manure.

It is not, however, merely for the purpose of removing deteriorated earth or adding manure, that shifting is important; in all potted plants the ball of earth, by the continual passage of water through it, is in time reduced to a state of hardness and solidity unfavourable to the retention of moisture or the growth of roots, and this is of course cured if the operation of shifting is judiciously performed. I must, however, confess I have seen gardeners contented with lifting a plant with a hard old matted ball, out of one pot into another of a little larger size, shaking some particles of fresh earth in between the ball and the side of the pot, and pressing the whole down with as much force as the thumbs can give. Do such men deserve the

name of Gardeners?

It is found that the roots of potted plants invariably direct themselves towards the sides of the pot, as must indeed neces sarily happen in consequence of their disposition to grow horizontally. Having reached the sides, they do not turn back, but follow the earthenware surface, till at last they form an entangled stratum enclosing a ball of earth; then, if not relieved by repotting, they rise upwards towards the surface, or they attempt to force themselves back to the centre. The greater number of roots are, however, always found in contact with the porous earthen sides of the vessel; and especially all the most powerfully absorbent, that is to say the youngest, parts. They are, therefore, in contact with a body subject to great variations of temperature and moisture, in consequence of exposure to the sun, or to a dry air in motion, unless in

those cases where the air is kept, by artificial means, shaded and uniformly damp. The extent of these changes gardeners are hardly aware of; a few years ago I found in a conservatory, in the months of May and June, that the temperature of the soil in a small flower-pot was as low as 40° at one period of the day and as high as 90° at another period. In a dry summer day, when the leaves are perspiring freely and requiring an abundance of water from the roots, the latter are placed in contact with a substance whose moisture is continually diminishing; or in a greenhouse, where the pots are syringed, the heat of the earth in contact with the roots is lowered by a copious evaporation from the sides of the pot, just when, in nature, the bottom-heat should be the greatest. The evil consequences of this are well known to gardeners, who however often neglect taking sufficient precautions to prevent it. Greenhouse plants exposed to the open air in summer always suffer severely from the irregular condition of the sides of the pots, whence the common practice of plunging them in the earth, for the purpose of bringing them into the condition of plants growing in the open ground.

This is, however, attended with some disadvantage, for the plants root, through the bottom of the pots or over the edges, among the earth in which they are plunged, and when taken up in the autumn for removal they must have all such roots cut off again, for there are no means of bringing them within the limits of a pot. For these and similar reasons, no good gardener will expose his greenhouse plants to the open air in summer, if he can help it, unless they are duplicates, or unless there is some object to be attained very different from the strange notion that they are rendered more hardy by the process. The effect that is really produced upon them is to give them a sort of artificial winter in summer, that is to say to expose them to a period of comparative rest from growth, which in many cases is useful, or to expose them more fully to the sun at a time when they are ripening fruit. Mr. Knight assures us that by having the sides of their pots exposed fully to the air, the taste and flavour of the Peach and Nectarine, and still more of the Strawberry, are greatly improved, and the Fig-tree in the stove is made to