- Oct 27, 2011
- Reaction score
- Victoria Australia
Thanks terry. For those people growing plants in 'still' water ..... with roots in water that just sits there (eg. those people doing the 'full water culture' thing) ------ is that a case where the plant can eventually run into issues if the concentration of free oxygen becomes too low? I'm suspecting that the FWC group probably change their water every once in a while.Orchid roots need oxygen to stay alive and function. Oxygen is not transported to the roots from the leaves, so it must be available in the root zone. It is not water that kills orchid roots but lack of oxygen.
Since air can constantly diffuse into a volume of water in a container, that must be the source of any ongoing oxygen. Roots that can accommodate to low oxygen water must have a lower metabolic rate, and probably lower function.
Thanks for sharing that important and most excellent knowledge Terry. This really clears up a lot of things. Important things.the roots that are completely submerged in water are getting oxygen from the water until there isn’t any.
The poor quality LECA I have does not hold any water at all and in fact quite a lot of the pellets have an annoying habit of floating in water. The only info I have about Atami B'cuzz Hydro-Rokz suggests that at least some water is taken up into the core of the pellets, can you confirm this ? Also can you remember the approximate average diameter ?LECA is Lightweight Expanded Clay Aggregate, and it was developed in Europe for use as an aggregate in lightweight concrete, allowing concrete building to be constructed taller. It was later co-opted for hydroponic growing.
Atami's B'cuzz Hydro-Rokz is probably the best one out there, as it was reengineered specifically with hydroponics in mind.
In reverse order:The poor quality LECA I have does not hold any water at all and in fact quite a lot of the pellets have an annoying habit of floating in water. The only info I have about Atami B'cuzz Hydro-Rokz suggests that at least some water is taken up into the core of the pellets, can you confirm this ? Also can you remember the approximate average diameter ?
After soaking the original Hydroton brand for several days, only 20% have sunk. It was first rinsed, then boiled 5 minutes. Is there something I’m missing?In reverse order:
The standard size for most LECA brands is 8-16 mm and that's about right for Hydro-Rokz. When I imported 40' shipping containers of it, it was graded at 10-16 at my request.
Yes, it absorbed water very well. After selling off all my plants before moving, there were a few ratty-looking ones that were destined for the dump. It was a good six weeks before the guy buying the greenhouse came to disassemble it and I didn't go out there once to water. Those in the LECA showed no signs of dehydration whatsoever, because there was enough moisture stored in the LECA to keep them going.
That said, most brands of LECA will do the same, given time to soak. I recently prepare some some Hydroton, and about 20% floated initially, but after a day, most had sunk.
Why boil it?After soaking the original Hydroton brand for several days, only 20% have sunk. It was first rinsed, then boiled 5 minutes. Is there something I’m missing?
My experience with growstone is too short duration to form an opinion. I like using it with something equal size that hold water like the Coco croutons. I like that they are from renewable resources. I use gravel, pebbles, charcoal, lava rocks also as inerts, non deteriorating, but not alone except for epiphytes. I think of paphs as terrestrial/lithophyte of a wet region and I have mine in aquatic plant pot in a finer size mix with orchiatta bark. The seedlings in pure bark.I've been out of town, so waited to respond on the computer rather than the phone or tablet. Good discussion.
To the person growing in Growstone, how is that going? I'm sorry that it isn't made anymore, but not a surprise. I have some in my potting shed. Ray, perhaps you can shed some light on this. It was my understanding that you had tried this, and found it too alkaline. However, I've wondered if for Paphs that grow on limestone in nature if that would be an advantage rather than a disadvantage. Any comments?
I'd like to know a LOT more about orchid roots than I do now, as I believe healthy roots are the most important key to good orchid growing, and that most of us don't understand how epiphytic roots work very well, the morphology and anatomy, particularly as it relates to velamen. Does anyone (terryros?) have any recommended reading, particularly that is scientifically informed. I'd like to know if anyone has actually experimented with the notion that the roots (velamen?) develop differently in very wet media or water than they do in other environments, and when that causes difficulty when moving into a dramatically different medium. For example, I have purchased some Phals from Norman's in the past. They are always in plastic in moss. If I leave them in that, the roots tend to rot. If I move the plant and moss into a clay pot, they do fine, but the roots mostly grow next to the moss, and the center of the ball has no roots. Wet plus air? But I can also move them into what I call dry semi-hydro (very little reservoir) and they also do fine growing in what is mostly a damp to dry medium with humidity. I suspect this is not dissimilar to what Alan Koch does at Gold Country with Catts--moss (usually in plastic, as it's much easier to ship), but only in the top of the pot, with air beneath.
And how does air get to the roots (or at least the velamen)? Is it mostly through water, or do they need "real air" too? Some genera are believed to prefer a wet/dry cycle (including at least some of the CAM plants that are almost succulent in nature) but can also develop "water tolerant" roots? I have also seen roots have part of the velamen literally rot away while the living root continue to grow. In fact, when I repot, I tend to strip off rotten velamen and not worry about the actual stringy root very much--green is probably still alive, brown can still anchor the plant even if dead and doesn't seem to add that much "rot" at the base.
I tried A & P's Infini-Mix when I still lived in Seattle and another grower there seemed to use it quite successfully. He said it dried out quickly. Mine never did, and I had rotten roots. I have a bit left, and may try it again, but again, better in plastic or clay? So many variables, and yet healthy roots are essential. Well, probably enough for now.
One more thing. Alan Koch says that orchid roots have stomata, which is, I believe, the way plants take up oxygen. He did not say if this was the root itself or the valamen, but some mechanism like this would be required for the roots to breathe. Only open at certain times of day? I'd love to see some scientifically informed literature on this. He also said that they photosynthesize. Again, true? If so, cutting off light to the roots might not be a good thing. After all, growing orchids in pots is not natural, and their adaptations might be contrary to what we are doing to them for the sake of convenience.