Organic Chemistry in its Applications to Agriculture and Physiology, Justus Liebig. 1841, p 386-389.


“In a division of a low hothouse in the botanical garden at Munich, abed was set apart for young tropical plants, but instead of being filled with tan, as is usually the case, it was filled with the powder of charcoal, (a material which could be easily procured,) the large pieces of charcoal having been previously separated by means of a sieve. The heat was conducted by means of a tube of white iron into a hollow space in this bed and distributed a gentle warmth, sufficient to have caused tan to enter into a state of fermentation. The plants placed in this bed of charcoal quickly vegetated, and acquired a healthy appearance. Now, as always is the case in such beds, the roots of many of the plants penetrated through the holes in the bottom of the pots, and then spread themselves out; but these plants evidently surpassed in vigor and general luxuriance, plants grown in the common way, for example, in tan. Several of them, of which I shall only specify the beautiful Thunbergia alata, and the genus Peireskia, throve quite astonishingly; the blossoms of the former were so rich, that all who saw it affirmed they had never before seen such a specimen. It produced, also, a number of seeds without any artificial aid, while in most cases it is necessary to apply the pollen by the hand. The Peireskiae grew so vigorously, that the P. aculeata produced shoots several ells in length, and the P. grandifolia acquired leaves of a foot in length. These facts, as well as the quick germination of the seeds which had been scattered spontaneously, and the abundant appearance of young Filices, naturally attracted my attention, and I was gradually led to a series of experiments, the results of which may not be uninteresting; for, besides being of practical use in the cultivation of most plants, they demonstrate also several facts of importance to physiology. "The first experiment which naturally suggested itself, was to mix a certain proportion of charcoal with the earth in which different plants grew, and to increase its quantity according as the advantage of the method was perceived. An addition of 2/3 charcoal, for example, to vegetable mould, appeared to answer excellently for the Gesneria, and Gloxynia, and also for the tropical Aroideae with tuberous roots. The two first soon excited the attention of connoisseurs, by the great beauty of all their parts and their general appearance. They surpassed very quickly those cultivated in the common way, both in the thickness of their stems and dark color of their leaves; their blossoms were beautiful, and their vegetation lasted much longer than usual, so much so, that in the middle of last November, when other plants of the same kinds were dead, these were quite fresh and partly in bloom. Aroideae took root very rapidly, and their leaves surpassed much in size the leaves of those not so treated: the species, which are reared as ornamental plants on account of the beautiful coloring of their leaves, (I mean, such as the Caladium bicolor, Pictum, Poecile, &c.,) were particularly remarked for the liveliness of their tints; and it happened here, also, that the period of their vegetation was unusually long. A cactus planted in a mixture of equal parts of charcoal and earth throve progressively, and attained double its former size in the space of a few weeks. The use of the charcoal was very advantageous with several of the Bromeliaceae, and Liliaceae, with the Citrus and Begonia also, and even with the Palmae. The same advantage was found in the case of almost all those plants for which sand is used, in order to keep the earth porous, when charcoal was mixed with the soil instead of sand; the vegetation was always rendered stronger and more vigorous.

*The cuttings of several of these plants being full of moisture, require to be partially dried before they are placed in the soil, and are with difficulty made to strike root in the usual method. The charcoal is probably useful from its absorbing and antiseptic power. The Hakea is extremely difficult to propagate from cuttings. All the Laurus tribe are obstinate, some of them have not rooted under three years from the time of planting.—W.

"At the same time that these experiments were performed with mixtures of charcoal with different soils, the charcoal was also used free from any addition, and in this case the best results were obtained. Cuts of plants from different genera took root in it well and quickly; I mention here only the Euphorbia fastuosa and fulgens which took root in ten days, Pandanus utilis in three months, P. amaryllifolius, Chamaedorea elatior in four weeks, Piper nigrum, Begonia, Ficus, Cecropia, Chiococca Buddleja, Hakea, Phyllanthus, Capparis, Laurus, Stifftia, Jacquinia, Mimosa, Cactus, in from eight to ten days, and several others amounting to forty species, including Ilex, and many others. Leaves, and pieces of leaves, and even pedunculi, or petioles, took root and in part budded in pure charcoal. Amongst others we may mention the foliola of several of the Cycadeae as having taken root, as also did part of the leaves of the Begonia Telfairiae, and Jacaranda brasiliensis; leaves of the Euphorbia fastuosa, Oxalis Barrilieri, Ficus, Cyclamen, Polyanthes, Mesembrianthemum; Also, the delicate leaves of the Lophospermum and Martynia, pieces of a leaf of the Agave Americana; tufts of Pinus, &c.; and all without the aid of a previously formed bud.*

"Pure charcoal acts excellently as a means of curing unhealthy plants. A Dorianthes excelsa, for example, which bad been drooping for three years, was rendered completely healthy in a very short time by this means. An orange tree which had the very common disease in which the leaves become yellow, acquired within four weeks its healthy green color, when the upper surface of the earth was removed from the pot in which it was contained, and a ring of charcoal of an inch in thickness strewed in its place around the periphery of the pot. The same was the case with the Gardenia.

†See an account of these experiments Loudon's Gardener's Magazine, for March, 1841

"I should be led too far were I to state all the results of the experiments which I have made with charcoal. The object of this paper is merely to show the general effect exercised by this substance on vegetation, but the reader who takes particular interest in the subject, will find more extensive observations in the "Allgemeine deutsche Gartenzeitung" of Otto and Dietrich, in Berlin.†

"The charcoal employed in these experiments was the dust-like powder of charcoal from firs and pines, such as is used in the forges of blacksmiths, and may be easily procured in any quantity. It was found to have most effect when allowed to lie during the winter exposed to the action of the air. In order to ascertain the effects of different kinds of charcoal, experiments were also made upon that obtained from the hard woods and peat, and also upon animal charcoal, although I foresaw the probability that none of them would answer so well as that of pine-wood, both on account of its porosity and the ease with which it is decomposed.

"It is superfluous to remark, that in treating plants in the manner here described, they must be plentifully supplied with water, since the air having such free access penetrates and dries the roots, so that unless this precaution is taken, the failure of all such experiments is unavoidable.

"The action of charcoal consists primarily in its preserving the parts of the plants with which it is in contact; whether they be roots, branches, leaves, or pieces of leaves, unchanged in their vital power for a long space of time, so that the plant obtains time to develop the organs which are necessary for its further support and propagation. There can scarcely be a doubt also that the charcoal undergoes decomposition; for after being used five or six years it becomes a coaly earth; and if this is the case, it must yield carbon, or carbonic oxide, abundantly to the plants growing in it, and thus afford the principal substance necessary for the nutrition of vegetables. In what other manner indeed can we explain the deep green color and great luxuriance of the leaves and every part of the plants, which can be obtained in no other kind of soil, according to the opinion of men well qualified to judge? It exercises likewise a favorable influence by decomposing and absorbing the matters absorbed [query, excreted] by the roots, so as to keep the soil free from the putrefying substances which are often the cause of the death of the spongiolae. Its porosity as well as the power which it possesses, of absorbing water with rapidity, and, after its saturation, of allowing all other water to sink through it, are causes also of its favorable effects. These experiments show what a close affinity the component parts of charcoal have to all plants, for every experiment was crowned with success, although plants belonging to a great many different families were subjected to trial."—(Buchner's Repertorium, ii. Reihe, xix. Bd. S. 38.)