See:
Does a bit of colloidal silver prevent rose cuttings in water from getting fungus?
Does anything else added to the water prevent fungus killing rose cuttings that you root in water?
Charcoal isn’t as exotic as silver, but here’s an oldie from Feast, one of the earliest breeders working with Rosa setigera.
Magazine of Horticulture 8: 83-85 (March 1842)
Nursery of Mr. Samuel Feast
“Some experiments upon the growth of plants in charcoal have been made here. Mr. Feast had quite a collection of Orchidaceae, and as they had not thriven any too well, it occurred to him that he might make use of the charcoal with good effect. The whole of the plants were consequently repotted in a mixture of peat and charcoal: this was done in June or July, and when we saw them in August, many of the plants were throwing out new roots with much vigor. The charcoal seems to act as a conductor and retainer of heat, and, by keeping the soil light and open, facilitates the rooting of the plants. Mr Feast has also tried charcoal in rooting plants from cuttings, and has succeeded in growing in this way Herbemont’s musk cluster rose, which he has been unable to multiply by cuttings, in the ordinary way.”
Charcoal worked very well for me when I was growing Amaryllises.
Another, more recent report:
Biotechnol Adv. 2008 Nov-Dec;26(6):618-31.
The role of activated charcoal in plant tissue culture.
Thomas TD
Abstract
Activated charcoal has a very fine network of pores with large inner surface area on which many substances can be adsorbed. Activated charcoal is often used in tissue culture to improve cell growth and development. It plays a critical role in micropropagation, orchid seed germination, somatic embryogenesis, anther culture, synthetic seed production, protoplast culture, rooting, stem elongation, bulb formation etc. The promotary effects of AC on morphogenesis may be mainly due to its irreversible adsorption of inhibitory compounds in the culture medium and substancially decreasing the toxic metabolites, phenolic exudation and brown exudate accumulation. In addition to this activated charcoal is involved in a number of stimulatory and inhibitory activities including the release of substances naturally present in AC which promote growth, alteration and darkening of culture media, and adsorption of vitamins, metal ions and plant growth regulators, including abscisic acid and gaseous ethylene. The effect of AC on growth regulator uptake is still unclear but some workers believe that AC may gradually release certain adsorbed products, such as nutrients and growth regulators which become available to plants. This review focuses on the various roles of activated charcoal in plant tissue culture and the recent developments in this area.
I did a rough controlled experiment, tried rooting some cuttings from a rose I grew from seed (though I suppose if I wait until autumn I might have some more seeds). I tried some cuttings in water with a bit of colloidal silver, and one cutting I put in water with a dissolved aspirin tablet. The cuttings with colloidal silver grew roots, and the cutting with aspirin shrivelled and died. The colloidal silver cuttings did take quite a long time to grow roots though, a few weeks. They didn’t rot, and I hadn’t changed the water.
I have tried to take cuttings before from this seed-grown rose with zero success, using the usual method of hormone rooting powder and potting compost.
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Karl, thanks for that information about Charcoal. I have some odd bits of activated charcoal lying around, I might give it a try.
Maybe as you say it is about heat and possibly oxygen, or its surface area, or some sort of catalyst.
Hmmm. That paper apparently describes an in-vitro propagation method for roses. There are not many of those.