The Friend 16(2): 10-11 (1842)

Some of the gardeners and scientific men of Germany, have within a few years interested themselves in a series of experiments upon this subject, conducted at the royal botanic gardens of Munich, by Edward Lucas of Erfurt, assistant gardener. The results are highly curious, and may probably be turned to good account by cultivators in this country. Professor Zuccarini of Munich, mentions that by the use of charcoal, shoots of plants, leaves, parts of leaves, calyces, &c. may be made to grow, even of plants that seldom or never make roots in the usual way of treatment.

He states that Lucas, in the spring of 1839, discovered that several plants in a hot-house that were plunged in refuse of charcoal, showed an extraordinary vigour of growth, as soon as they had pushed their roots through the holes in the bottom of the pots, into this under stratum. This observation led to a set of experiments, which quite astonished himself, and the scientific friends who encouraged him to prosecute them.

He at first used the refuse of charcoal, too fine to be burnt, from which he sifted the coarser pieces by a coarse earth seive. He found that to answer best which had been exposed for some months to the influence of the air and weather. In such charcoal, unmixed with any other material, he succeeded the first season in getting cuttings of many plants to grow; he names sixty-six kinds; among them Euphorbias, Begonias, Cacti, and other succulent plants, black pepper and the bread fruit. The unsuccessful experiments were few Compared with the successful. From parts of leaves he succeeded in getting a considerable variety of plants to vegetate; he enumerates twenty-nine, including a species of Euphorbia, two of Begonia, and the sweet potato. All the species of Gloxinia grew, even from a flower-stem or a calyx. A species of pine (Pinus excelsa,) grew from the leaves.

He then mixed various kinds of earth with the charcoal, and still bad the most extraordinary results. He says that all the plants he subjected to this treatment, were as much distinguished by their luxuriance, as by the more perfect development of their individual parts. This was particularly the case with tuberous rooted plants, which besides their perfect development, had also a much longer period of vegetation; so that the difference in this respect, between those that were cultivated in their usual soil, and those which had a mixture of charcoal, amounted to nearly two months. Orange trees with yellow leaves, having had a layer of charcoal laid on after the upper surface of earth had been removed, soon recovered their green colour; this was also the case with some other plants. He was not very particular as to the proportion of earth he mixed with charcoal, but generally found half of each to do very well, always taking care that the coal had been exposed for some time to the weather, and that timely watering was never neglected, as the porosity of the earth causes it to dry quickly. An old and sickly plant of the Doryanthes excelsa, which had been declining for two years, and had no roots left but one old and decayed one, was planted in one third charcoal. In three weeks it began to grow, and finally recovered perfectly.

Lucas, in an essay written within a year, mentions that many gardeners not having succeeded in their experiments, charcoal had fallen into disrepute among them; but he believes that in every case the failure was owing to the manner of applying it, or to the quality of the coal itself. He has found that in many cases, particularly when used in pots, as soon as the capillary vessels of the charcoal are full, a farther supply of water is useless and injurious; when mixed with soil, however, it requires more frequent watering. But the chief cause of failure was the fineness of the charcoal, by which its most valuable qualities,--capillarity, capability of condensing gases, and porosity, were lost.

Many new plants, of which he names seventy-two, some very difficult sorts to root, had grown in charcoal, since his last published essay. He mentions four kinds of magnolia, a myrtle, Canada pine, Indian azalea, an erica, the tendrils of a grape, the oleander, and two kinds of medicinal guaiacum Among the plants he names, are species of the most opposite families, and most of them rooted much easier than in sand or earth; with some, no trial of the usual methods of propagating had before been successful at the botanic garden of Munich. He had not made much use of charcoal in sowing seeds, but when applied, it had proved very efficacious. He had made experiments upon the fitness of charcoal for packing plants for transportation; and for this purpose some young chamoedoreas, ferns, calceolarias, salvias, verbenas and young cabbage and cucumber plants, some with moss round the roots, others without any covering, were put in dry or very slightly moistened charcoal, firmly pressed down, and the closed box placed for four weeks in an airy shed, on which the sun shone for several hours; at the expiration of this period, the palms and ferns were found in a very flesh state; the calceola rise end salvias had some yellow leaves, but had made young shoots; a species of petunia, even flowered on the box being opened; the verbenas only had offered, but were still alive; the young cabbage and cucumber plants taken out of dung beds had rotted, but without injuring any of the plants lying beside them; cut flowers of many different sorts kept perfectly fresh in pure dry charcoal, for from eight to fourteen days. Radishes, parsnips, onions, and the turnip-like roots of oxalis lasiandra, Zucc. attained a considerable size in a bed filled one foot deep with pure charcoal; the roots of tulips which had produced flowers in the spring, being planted in the same bed, flowered again perfectly well late in the autumn.

To prove if any difference existed with respect to the efficacy of different sorts of charcoal, the garden inspector, M. Seitz, had charcoal made from eight kinds of wood, viz., oak, linden, ash, beech, alder, willow, elm and fir. They were found to have almost exactly similar effects. It was very different with animal charcoal, which in this experiment produced the most favourable results; many leaves rooted in them which had not succeeded in the wood charcoal, and some very soon produced shoots.

Zuccarini says that those leaves were found to vegetate most freely which had strong prominent veins. The cut ends of these being placed in the charcoal, a small tuber or callosity formed upon the extremity of each. These attained the size of a large pea before putting out roots, and from them proceeded the germ or shoot which formed the new plant; each vein thus producing a separate plant. He found it of advantage as soon as the growth of the tuber was sufficiently advanced, to remove the cutting from the coal into a proper sort of mould, and, by this means, the little knob being able to provide its own nourishment, will prevent the untimely exhaustion of the parent leaf. If this precaution is delayed, an entire stoppage takes place in the growth; the knob produces neither roots nor buds, and dies; because the parent leaf cannot yield any more nourishment; and the charcoal appears to him to have a preserving and stimulating, rather than a nourishing quality.

W. Neubert of Tübingen discovers, however, that by the use of charcoal, plants thrive permanently in much smaller pots than heretofore. He had primulas, eight years old, with stems a foot and a half high, growing and blooming luxuriantly in pots of two inches diameter. He transplants them every autumn, and takes away half the ball of roots and all the side shoots, and is careful to keep them tolerably moist. He finds his plants (quite the reverse of Lucas's experience,) produced much fewer roots than usual, and conjectures that this may be owing to his having used beech coal instead of fir, as Lucas did.

Dr. Buchner undertakes to explain upon scientific principles, the wonderful effects of charcoal. He ascribes them in part to the power possessed by that substance of absorbing light and heat to a very great degree, in consequence of its dark colour and extreme porosity; and also to its capacity for absorbing atmospheric air. Among all the bodies capable of absorbing gases and vapors, charcoal has been proved by numerous experiments, to hold the first rank. Consequently, when long exposed to atmospheric action, it imbibes many qualities highly conducive to vigorous vegetation, and is the means of conveying to the roots of plants, besides light and heat, nitrogen, hydrogen and oxygen in great abundance.

He remarks that for a long time it was generally supposed, that charcoal, as an inanimate body, incapable of decay, contributed in no degree to the nourishment of plants, and that charcoal dust could only serve, at most, to make the earth looser and warmer. But Lucas found that the charcoal in which plants grew, by degrees underwent decomposition.

Judging from the effects of charcoal on vegetation, its antiseptic properties are of great importance. It has very little power of retaining water; and this property deserves great attention, in respect to recovering the health of plants which have been injured by being in a clayey soil, or too freely watered, or after continued rain, or being in contact with manure not sufficiently decomposed.

Lucas has not confined his experiments to coal. He has for six years been making use of snow in the germination of certain kinds of seeds, chiefly those of alpine plants. He first put into pots a portion of earth, the most suitable to the kind of plant to be cultivated; then a layer of snow, then the seed, and covered it with another layer of snow. He then set them in a box covered with glass, and placed it in a temperature of 59° to 60° Fah., in which the snow melted. Many of the seeds germinated in two days. He even succeeded with the purple crotalaria, which he had never done before by any other method. After germination, he sprinkles a little sand over the seed.

Professor I. Liebig, of Gieseen, who has devoted so much learned research to agricultural chemistry, is of opinion, "that the loose formation of the snow, which allows of an uninterrupted admission of oxygen; the exclusion of those foreign agents which are always found in a soil that contains corrupted vegetable matter; and finally the volatile alkali of the snow,—all these causes combined, effect the remarkable appearance of germination in this process."