Here are a couple of excerpts from the gesneriphile list. A conversation was started a while ago about using "old" or pre-used water for starting cuttings, especially as it was related to gesneriad cuttings. The questions were posed about why anyone would want to use water that had already been sitting around with a cutting starting in it. Wouldn't this be spreading disease or at the very least, wouldn't clean water give the plants a better start. The answers were quite interesting. I'm very grateful for such intellegent and interesting discussion on the list... these comments came from primarily two members, Ingrid and Vincent.
Vincent and Dale were talking about how old water was better for starting cuttings. Was surprised that nobody posted to the list the simple answer to that fact: rooting hormones are water soluble and will boost the new cutting before it has had the chance to make its own. No need to buy them in a powder that is mostly fungicide. There is an old woman´s trick in Sweden, to add a pea to the glass of water with the cutting. The pea will send out roots quickly and make the cutting do the same faster than usual. One of our young members was shocked to see me recycle the water when I gave her a bunch of rooted kohleria cuttings. She has a grandmother, and still was not told. The world as we know it is coming to an end!
Happy growing to all!
Thank you for mentioning the hormones. In my long post, I mentioned that having already-rooting plants in the same container was best yet... and alsmost went into the stories of using willow cuttings as rooting hormone. I cut that part out before finishing because I'd already written so much, and felt that I should review the little research I'd done to avoid repeating myths & hearsay. I don't remember enough details. I do remember that I read of a controlled study showing that many other plants besides willow, in closed systems (like the containers we're talking about) will leave rooting hormones in the water they're growing in, and those do have some effect. The unrooted willow extract was less conclusive in that study. Wish I could find the references now but that was many years ago! So even though I left that out, I believe you are right and experience, even some science, has shown us the truth of this, over many years as you point out :) I would also think that the rooting peas would help with the aging of the water in other ways in addition to the hormone effect. I will try that one too! Another reason I focused on the microscopic life instead is that so many are unaware of the processes. In one of the many complex interactions in a new or relatively sterile environment, organics like protein are broken down to produce ammonia in the early stages, which is toxic and inhibits new root growth. This can be the main reason many seeds and cuttings will not take in fresh soil mix, but will be fine after it is aged. Once the various nitrifying bacteria and other things are in balance, ammonia is "eaten" by those bacteria, and converted quickly to less damaging nitrates which, can be absorbed as food. Reading old texts from European glasshouse growers you'll find the advice to age new, or newly pasteurized, compost for cuttings and sowing seed, repeatedly. Green plants can use ammonia as nitrogen food too, but if the levels get anywhere near where you could smell it, it can kill the plants. Very sensitive new roots and seeds han handle even less, you'd need a chemical test kit to detect those low but still toxic levels (as we use in new aquariums, to be sure they are safe for fish). Online searching for "nitrogen cycle" and for _natural rooting_ can give anyone interested, lots of information both technical and experiential. Being cautious of spreading diseases of course, old water is definitely the way to go for IMO. Caution for me means thing like being sure (as possible) that there was no disease on previous cuttings, using water from unrelated sources (healthy aquariums, water aged using pasteurized materials, and dropping cuttings into old established terrarium water features. Some disease, especially bacterial end rots, can be cured by cutting off obvious infection, cleaning the cutting well, and placing in water teeming with established life. The disease seems to be overtaken by the healthy balance surrounding it. All of this is tossed out the window when doing micro propagation in a sterile container. but that's WAY too much work for simply rooting a gesneriad cutting!