Old Cattleya rhizomes may produce new roots. Some Catts normally produce new roots from the new rhizome just formed on new growth; others normally produce new roots from the older rhizome just before the new growth. When back bulb divisions are potted up, many Catts make new roots from the old rhizome as the new eye breaks.

If successful in the glass of water, I have observed new roots form on the rhizome before the eye breaks.

The plump back-bulbs of large Cattleya typically shrivel significantly after repotting and usually don't become fully plump again. This suggests that the roots they produce never become sufficient to sustain the bulbs. Perhaps this is the reason for Ray's focus on growing the eyes. I assume he will clarify.

The old back bulbs don't plump up, but the roots sustain the new eye.

Good point. The eyes usually don't get roots until they are fairly long.
K-Sci

Yes. That's my "take", anyway. Besides, both KLN and KelpMax are stimulants, and it is possible to over-stimulate a plant to death (that's how the auxin herbicide 2, 4-D works), so if you want to be safer about it, why use the one with less chance of getting the rhizome to grow?

K-sci, your climate is similar to mine. As long as that back bulb section remains together, and you have some viable dormant "eyes" (lateral meristems), you have a reasonably good chance at producing new growths. Even better if there are at least some living roots.

If I understand your first post, you have them them in a greenhouse, bare riot, no pot. We are already in tropical storm season, consider putting them outdoors in shade to catch the prolonged rain that comes with tropical systems. If the plants can absorb water at all, those are the conditions that are most likely to hydrate the plant and allow growth. I tie Cattleya back divisions up in tree branches this time of year, I have fairly good success getting them to root and grow this way.

Backbulbs that have lost all their roots can become rehydrated again but the more vigorous the hybrid the more noticebale it will be, ie it does depend on how many new roots the orchid can produce which can take years in which time the backbulbs could become even more dehydrated.

I would like to introduce exhibit "A":

http://www.orchidboard.com/community...1&d=1626522260

It's a Cattleya Orange nugget if anyone is interested, good strong root producer. and when I bought it is was severely shrivelled. It produced new roots and slowly slowly the backbulbs have regained plumpness. It's a shame I don't have a picture of what it used to look like but you can maybe judge by some browning on the bulbs how severely shrivelled it was, the furthest left bulb has not plumped up completely yet but is more plump.

Notice the roots required, this one really put out the roots in order to do this so if you have a not so vigorous root producer maybe the backbulbs can never get plump any time soon but it can be done and this one is now ready to be divided whereas before the backbulbs were too shrivelled.

Yes, and all the dandelions in your yard go to seed at once. Hmmm, maybe I should try a low dose of 2,4-D.(kidding);)

I've seen plenty of evidence that KelpMax works (see attached n=2 experiment results), but I'm not convinced that any rooting agents actually work on orchids. I thought I'd give KLN a try. If they grow to death, I won't use both next time. ;)

Thanks for your replies.

k-Sci

I have several. I cut all the dead roots off some and left the dead roots on others as an experiment. One of them has an inch or so of live root.
Let's try it. I grabbed two C. violacea 'Muse' backbulb racks, one with all the dead roots removed and one with dead roots still on. Just now I put them in baskets and hung them from a Bald Cypress with my Vanda. Pictures attached.

I don't understand that at all.

The roles of auxins & cytokinins are well-established in all vascular plants. The fact that they may not appear to work might be attributable to the quality of the product used (water-soluble auxins are prone to rapid degradation) or the expectations of the user. (I once had an Amazon KelpMax customer request a refund because he saw no root growth within a few days of application...)

For purposes of discussion, I classify stimulants in one of three ways, "direct", "indirect", and "shortcut".

Products containing auxins and cytokinins - KLN, Superthrive and others - are direct stimulants. They artificially boost the concentration of the hormones in the plants' system, stimulating action. Overdosing can lead to flower deformation (I've done it. Fortunately, it's reversible), stunted growth, "leggy" growth (if the cytokinins are in greater concentration than the auxins), or plant death.

Mega Thrive is an “indirect stimulant”. It is a urea-based foliar treatment that contains “mega” doses of molybdenum and boron. By delivering high doses of those trace elements, the plant is stimulated into producing auxins that stimulate root growth. Anecdotally, it seems to work well, but there are some potential down-sides to it’s use: one is the possibility of killing the plant by overdosing those trace elements, another is the flower deformation/stunted plant growth thing from the boosted auxins, and a third is the possibility of killing a child or pet that may chew on the plant, as the molybdenum makes the plant itself toxic.

Some probiotics might be considered "indirect stimulants", as many bacteria species secrete indole-acetic acid, an auxin that stimulates root growth, but generally, I think it's better to simply expect them to be "protectors" more than anything else.

There are species in Quantum-Total that are nitrogen-fixing and photosynthesizing, so they produce food and fuel from right within the plant, without it having to expend its own resources to do so, so that might also be construed as a "shortcut" stimulant.

That is also where I place KelpMax, which is, without a doubt, the safest and most effective stimulant available. While it does contain some natural hormones, making it "direct", it’s level of stimulation is far greater than one would expect for the amount contained, and that has been attributed to the other plant growth regulators, vitamins, amino acids, alginates and other polysaccharides present in the kelp juice, which can be used immediately - sort-of like an IV. Unlike other kelp extracts, those "shortcut chemicals" are not destroyed during production. Even the producers don't have a solid handle on the product's action, but laboratory and field studies all confirm its efficacy.