The Gardener's Magazine June 1841, p. 304-305.

ART. III. Continuation of the Experiments of the Effects of Charcoal on Vegetation, made in the Royal Botanic Garden of Munich.
By M. EDWARD LUCAS, formerly in the Munich Botanic Garden, and now Botanic Gardener at Ratisbon.

(From the Garten Zeitung for 1841, p. 25.)

ENCOURAGED by the universal interest which the application of charcoal in the cultivation of plants has awakened, I venture to lay before the reader the result of continued observations and experiments. This subject excited much curiosity in the course of the year; mention was made of it in a great number of papers, and experiments set on foot in many gardens of which I was an eye-witness. Success did not always equal the expectations formed of it; a circumstance, however, which is no disparagement to the efficacy of charcoal; for, in every case, either the manner of applying it, or the quality of the charcoal itself, was the cause of failure. In consequence of this, charcoal lost its repute in many gardens, while in others, where at first no experiments succeeded, it is, by persevering in the treatment, now applied to most sorts of plants. By some I was not sufficiently understood, particularly in my remarks on the moisture necessary for the charcoal, and hence the complaint that every thing damped off. I confess that I have spoken too loosely on this head, and, perhaps, have said too much; as in many cases, and particularly when used in pots, as soon as the capillary fibres of the charcoal are full, a superfluity of water would be useless or even injurious to the plants; when mixed with the soil, however, it requires more frequent watering than would otherwise be necessary. The chief cause of failure arose from having the charcoal too finely pulverised; by which its chief properties, capillarity, capability of condensing gases, and porosity, were lost. I was also reproached with having brought forward so old a subject; to this I reply that to me and to most lovers of plants it was certainly new: but I quote in proof of that assertion a passage from Schrank's Natural History of Plants, to which my attention has been called: "Senebier found that leaves in carbonated water, or when mixed with tincture of gall-nuts, vegetate longer and better than when in common water. He also found that leaves which, when exposed to the sun in water, had ceased to develope oxygen, did so again, as soon as carbonate was added to the water. In some parts of Sweden the barley-fields were manured with charcoal, and the crop was twenty times more abundant. Rafn found that the different sorts of corn grew best in the sorts of earth in which charcoal predominated." Leuch's Vollstandiger Düngerlehre, ii. 1852, p. 310. to 319. and p. 541. to 550., is said, according to the Allgemeinen Anzeiger der Deutschen, to contain observations on charcoal; but I have not been able to get a sight of this book.

During the last year many interesting cuttings of plants rooted in pure charcoal, some of them very difficult sorts to root, of which the following are examples: Dodonaea humilis, Corraea alba, C. rufa, Magnolia purpurea, M. glauca, M. humilis, M. fuscata, Myrtus moschata, Eutaxia Baxteri, E. myrtifolia, Chorozema Manglesi, Prunus Laurocerasus, Polygonum complexum, Halesia tetraptera, Witsenia corymbosa, Laurus Benzoin, PolygaIa cordifolia, Taxus macrophylla, T. baccata, Pinus canadensis, Andrewsia glabra; several species of Melaleuca, Diosma, Phylica, Grevillea, Chironia; Azalea indica, &c., Erica ignescens, tendrils of Vitis vinifera, Nerium Oleander, &c. Also of hothouse plants, Jacquinia arborea, J. mexicana, J. armillaris, Ilex paraguaiensis, I. acutangula, Malpighia Aquifolium, M. glabra, M. coccifera, M. fuscata, Ardisia japonica, A. colorata, Citrus buxifolia, C. Aurantium, C. Medica, Limonia trifoliata, Gualacum sanitum, G. officinale, Franciscea Hoppeana, Bauhinia aculeata, Stiffia insignis, Illicium anisatum, I. floridanum, Shotia speciosa, Comocladia integrifolia, Copaifera sp. Mexico, Plumieria lactea, P. angustifoIia, Gmelina sinuata, Chitonia mexicana, Laurus nitida, Inga Saman,  Quarea trichiliöides, Curcas drastica, Dombeya acerifolia, Schrankia aculeata, Buttnera catalpaefolia, Accia tamariscina, Karwinskia glandulosa, Chamaedorea Schiedeana Bactris setosa, Caryota sobolifera, Doryanthes excelsa, and others.

These examples may suffice; as they yield a sufficient proof that plants of the most opposite families root in pure charcoal, and mostly much better and easier than in sand or earth; and there are many of the sorts above mentioned which heretofore could not be successfully propagated in the Botanic Garden at Munich.

The propagation of Cacti in charcoal, again, produced the most favourable results. Most of the leaves and parts of leaves which rooted in charcoal produced eyes in the course of last summer, and in general not only one but several, from which shoots sprang, which are now grown into strong plants. As examples, I will only mention Vinca rosea, Vernonia tournefortiöides, Oxalis Mandioccana, O. Barrelieri, Thunbergia alata, Gonolobus mexicanus, Aristolochia brasiliensis, Euphorbia fastuosa, Eugenia australis, Ipomoea superba, Ardisia japonica, Fuchsia fulgens, &c. A number of similar leaves that have rooted have not as yet made shoots; they are, however, quite fresh, and full of sap, and have an abundance of roots. In most instances a protuberance was formed before the shoot was formed, and in many the eyes were close to the surface of the cut. The folioles of the Zamia integrifolia made three fleshy roots nearly 1 ft. long, and we may confidently expect that eyes will eventually be formed on them, though somewhat later.

Charcoal was not so much used for sowing seeds, but in cases where it was applied it showed extraordinary power. Cucumbers and melons, for example, germinated in it one day earlier than those sown in earth and plunged together with them in warm beds, and were strong plants; while the plants from the latter seeds continued stationary, though the treatment was the same.

Experiments were also made with a view to the application of charcoal in transmitting living plants; and for this purpose some young chamaedoreas, ferns, calceolarias, salvias, verbenas, and young cabbage and cucumber plants, some with moss round the ball of 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 fresh state; the calceolarias and 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 suffered, 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 of plants kept perfectly fresh and well in fine dry charcoal, for from eight to fourteen days. Radishes, parsneps, onions, and the turniplike roots of Oxalis lasiandra Zucc., attained a considerable size in a bed filled 1 ft. deep with pure charcoal; and also kohlrabi,, which was planted in it.

An interesting circumstance took place with the bulbs of the Duc van Thol tulip, which had been forced. In the month of May two bulbs of this species were put in the above-mentioned bed, to see whether they would become sufficiently strong during the summer to produce perfect flowers again next winter. In the beginning of November, when the bed was cleared out, both bulbs had produced large leaves 3 in. long, and showed evident proofs of flowering. They were put in pots in pure charcoal, and as early as the middle of November perfectly formed flowers appeared. There is no doubt, therefore, that for other early forcing bulbs this method would also be successful. In the same bed there was planted amongst others a fully grown scorzonera, which had been pulled up from a bed, and had lost part of its spindle-shaped root; it grew very well, and flowered.

Late in October, cuttings from very young shoots with flower-buds were made from some fine dahlias, nine tenths of which rooted in a short time. They were put in charcoal in large seed pans; at the bottom of the pans under the charcoal was one third leaf mould.

Some trees, such as Prunus Padus, Cytisus Laburnum, Fraxinus excelsior, Rosa centifolia, were, at the suggestion of Dr. Zuccarini, who has always encouraged me in my experiments, and taken the liveliest interest in them, taken up in their first growth, almost all their absorbing roots cut off, and planted in holes filled with charcoal. For some weeks they were quite fresh, then the ashes and bird-cherries began to languish, and the greater part of the leaves fall off; in the mean time the second growth began, but somewhat later, and not so strong; the Cystisus and the roses, on the contrary, continued to grow well.

I enclosed in a box, filled with half peat-mould and half charcoal, some plants of Daphne striata and D. Cneorum, which I had brought from the Alps, to prepare for sending them off afterwards. I succeeded in my object; these plants, which are apt to have their roots injured by the most careful taking up, and hence very seldom thrive with the usual method of cultivation and the mould used, had in a few weeks made new roots, and began again to grow. This treatment should always be applied to plants like these which are difficult to root. As a mixture, I have always used charcoal ashes successfully for all sorts of plants, and also seen it used in several other gardens; for example, for camellias, ericas, roses, pelargoniums, carnations, dahlias, palms, ferns, &c.; and I think that this use of it will become more general in districts where clay or chalk predominates, and where the mould used for growing plants is more compact than in sandy districts, and hence charcoal, as a means of producing porosity, must have a very favourable effect on the plants.

To prove if any difference existed with respect to the efficacy of the charcoal of different sorts of wood, the garden inspector, M. Seitz, had charcoal made from eight sorts of trees, viz. oaks, limes, ashes, beeches, alders, willows, elms, and firs. These sorts of charcoal were kept separate, and placed in a warm bed in a hothouse, to these a space filled with bone ashes was added. In all the nine compartments leaves of the same plants were put: the eight sorts of charcoal had almost exactly the same effects; if there were any difference, I would give the preference to the fir ashes. It was very different with the animal ashes: in this little experiment they produced the most favourable results; many leaves rooted in them which had not succeeded in the charcoal, and some very soon produced shoots.

I cannot resist saying a few words here, in conclusion of my observations, on the bed formed in the new propagating-house of the Royal Botanic Garden at Munich, built last summer. The house is sunk 4 ft. in the ground, is of an oblong form, and faces the E.S.E. The surface of the bed within is half a foot lower than the level of the garden, and is heated by a simple walled flue, over which a copper pan the length of the bed is placed, from which constant vapour arises, and which communicates heat and moisture to the charcoal, with which the whole bed is covered to the depth of 5 in., through perforated boards lying over the pan. The temperature of the water is, on an average from 50° to 60° of Reaumur (145° to 167° Fahr.). This sort of heating by water or steam is, in my opinion, the best method for propagating plants; and it is to be hoped that M. Seitz, from whose plan the house was built, will follow up his intention of giving a full description of it. I plunged my propagating-box, without a bottom, into this charcoal, and put the better sort of cuttings, and those which are difficult to root, in it. The movable lights were generally taken off during the night, and also sometimes in the day, that the moisture and drops of water might run off and be dried up. I stuck herbaceous cuttings in the bed without further preparation, and almost all of them grew easily and quickly.

In compliance with the wishes of several of my friends and patrons, I intend publishing in a small pamphlet all that has hitherto been known on the efficacy of charcoal, and I have already been promised communications on the subject from many quarters.