The suburban horticulturist (1842)
John Claudius Loudon

p. 248
670. Sowing seeds in powdered charcoal has been tried in the Botanic Garden at Munich with extraordinary success. Seeds of cucumbers and melons sown in it germinated one day sooner than others sown in soil, and plunged in the same hotbed; becoming strong plants, while the others remained comparatively stationary. Ferns sown on the surface of fine sifted charcoal, germinate quickly and vigorously; and it seems not improbable, that this material may be found as useful in exciting seeds difficult to germinate, as it is in rooting cuttings difficult to strike.

p. 263-264
603. Striking plants in powdered charcoal.—The use of sifted charcoal dust, or, in other words, of charcoal in a state of powder, with the particles not much larger than those of common sand, appears to have been first adopted for rooting cuttings in the Royal Botanic Gardens at Munich, by M. G. Lucas, in 1839. The details at great length will be found in the "Gardeners' Magazine" for 1841, translated from the Garten Zeitung. It may be sufficient here to state that powdered charcoal is used as a substitute for sand, and that it answers best when it has for some months been exposed to the air and weather ; also that it differs from sand in not only facilitating the rooting of cuttings, but in supplying them with nourishment after they are rooted, and consequently no under stratum of soil becomes necessary, as is the case where sand is used. The rationale of this practice has been given in the Garten Zeitung, by Dr. Büchner (sec Gard. Mag., 1841, p. 252), and the following summary is from a work recently published in London:—"It is essential to the rapid growth of a plant that carbonic acid should be taken up by its roots as well as by its leaves. The carbonic acid may be furnished in two ways; either the soil may absorb it from the atmosphere, or the decay in some of the matter contained in it may disengage this product. It is a remarkable property, possessed by several porous substances, of absorbing gases, and especially carbonic acid gas, to the amount of many times their own bulk. Of all these, charcoal is one of the most powerful in this respect, and it has been found that many plants may be grown in powdered charcoal, if sufficiently supplied with water, more luxuriantly than in any other soil. The charcoal itself undergoes no change, but it absorbs carbonic acid gas from the air; this is dissolved by the water, which is taken up by the roots, and thus it is introduced into the system. In such cases the plant derives its solid matter as completely from the atmosphere alone as if its roots were entirely exposed to it, for not a particle of the charcoal is dissolved; and it, therefore, affords no nutriment to the plants." (Vegetable Physiology, in a Popular Cyc, of Nat. Science, p. 117.) In the Gardeners' Magazine lists will be found of cuttings of a great many different species which had rooted in charcoal much sooner than they usually do in sand or soil; and from the most recent accounts it appears that the practice is still carried on in Germany with success. We would therefore strongly recommend its introduction into British gardens.