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Rockwool Cubes + LECA

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Geek_it

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Since Ken posted, I'll offer a little update on my experimenting.

As of maybe 6-8 weeks ago, 100% of my plants are in inorganic media; some in each of:
  1. 100% LECA in semi-hydroponic culture.
  2. 50% Rock wool cubes/50% LECA in semi-hydroponic culture.
  3. 50% Rock wool cubes/50% LECA in traditional culture.
  4. 100% Rock wool cubes in traditional culture.
Everybody seems happy - those in 100% cubes are a bit wobbly until the roots have really grown - and I am leaning toward the two 50/50 options as I move forward.
Hey rey, with the 50/50 mix, how long before it fries out and needs to top up with watering
 

Ray

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Hey rey, with the 50/50 mix, how long before it fries out and needs to top up with watering
I never "top up" anything. All waterings are floods, so that the medium is flushed and saturated with fresh material. Indoors, in my conditions, I water once every week to ten days - trying to keep it to a max of a week, but you know...
 

terryros

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Ray, what are you arriving at for fertigation concentration and frequency with the two 50:50 situations?
 

ScientistKen

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Thanks for update.
I get confused about terms. Is LECA the same as Hydroton or are they different brands?

I have tried 100% and it works, like you say it can be wobbly at first especially on small plants. Also wobbly when you initially plant if you plant with dry cubes before watering. I've done it both ways and there are pros and cons both ways. I like that the cubes provide some geometry and precision. It kind of makes up for the wobbly start because you can make adjustments.

I agree with your conclusion. I think I like the 50/50 better. It provides more air to the roots and helps reduce wobbliness. I have had best luck with besseae and kovachii hybrids. Lindleyanum have not had good color. There may be something else going on or it could be excess moisture or nutrient deficiency. This inert medium approach may be more fussy with nutrient deficiencies and pH. I plan to get some Kelp Max from Ray.
 

ScientistKen

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One more thing. For moss lovers, moss is almost automatic. The example I posted does not have much moss out of the ones I have growing this way. It's common to be solid moss at the top.
 

Ray

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Ray, what are you arriving at for fertigation concentration and frequency with the two 50:50 situations?
Terry,

I made the switch in some (most) of those just before coming indoors for the winter, so most of my experience is in a somewhat cooler, drier environment. I always water with K-Lite, and try to keep up with once a week @ 100 ppm N, but that has occasionally slipped a few days. Once a month I add KelpMax and Quantum. In the summer, when the plants are out on the deck, where it is much warmer, far for humid, and with brighter light (still indirect, as they’re along the north side of the house, just outside the Low-E windows they’re in front of now), I feed at 50 ppm N about twice a week.
Thanks for update.
I get confused about terms. Is LECA the same as Hydroton or are they different brands?

I have tried 100% and it works, like you say it can be wobbly at first especially on small plants. Also wobbly when you initially plant if you plant with dry cubes before watering. I've done it both ways and there are pros and cons both ways. I like that the cubes provide some geometry and precision. It kind of makes up for the wobbly start because you can make adjustments.

I agree with your conclusion. I think I like the 50/50 better. It provides more air to the roots and helps reduce wobbliness. I have had best luck with besseae and kovachii hybrids. Lindleyanum have not had good color. There may be something else going on or it could be excess moisture or nutrient deficiency. This inert medium approach may be more fussy with nutrient deficiencies and pH. I plan to get some Kelp Max from Ray.
LECA is an acronym for Lightweight Expanded Clay Aggregate, of which Hydroton is but one brand name.

I don’t consider inert media to be “fussy” about nutrition. If anything, I think it gives the grower more control, but then again, I’ve been growing in S/H culture for 30 years, so I’m kind of used to it at this point.
 

Sky7Bear

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I am also working with inorganic media, mostly semi-hydroponic, though I have a few in a 50/50 mix in traditional culture. I find that the top layer dries out to fast if I don't put some sort of "lid" on it--at the moment, small aquarium gravel. The beauty of growing this way is no more throwing away rotten bark (Terry Root used to repot 2 x a year at the Orchid Zone). What a waste of time and resources. Many of the Paphs and Phrags in nature are already growing at least partially lithophytically. Air to the roots is, I believe, an essential ingredient in any orchid culture, and probably the ratio varies by genus and perhaps in some cases even species. Thanks, Ray, for taking the lead on this and for doing your work scientifically and reporting it.
 

ScientistKen

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Scary light levels!
I kind of wonder about that. They are growing well, though. Came out of flask in September 2019, so 16 months. The biggest one has over 6" leafspan. I have another compot with mostly medium sized between the largest and smallest in this compot.
 

terryros

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I agree that oxygen is under appreciated and essential for roots. It is not transported down from the leaves. Large particle media like LECS, lava rock, river rock, etc give great air space for the roots, but require frequent fertigation. Each of us has to figure out the balance of watering frequency we can provide and maintenance of air space for the types of orchids we grow. Ray has shown us good data and a method for a roughly once a week fertigation by providing a water buffer with rock wool. If you can fertigate frequently, you could be moving toward all rocks.
 

ScientistKen

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I agree that oxygen is under appreciated and essential for roots. It is not transported down from the leaves. Large particle media like LECS, lava rock, river rock, etc give great air space for the roots, but require frequent fertigation. Each of us has to figure out the balance of watering frequency we can provide and maintenance of air space for the types of orchids we grow. Ray has shown us good data and a method for a roughly once a week fertigation by providing a water buffer with rock wool. If you can fertigate frequently, you could be moving toward all rocks.
I use river rock quite a bit. I like lava rock, but it often tears up roots at repotting. But from an oxygen standpoint, I think that has to be one of the best.
 

Ray

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If you do the math, 100% perfect spheres of the identical diameter offers the most free space. Anything that is irregular in shape or non-uniform in size has the opportunity to intrude into the spaces created by its neighboring particles, reducing that open volume. That is a good reason to avoid mixing coarse bark with smaller pieces of charcoal and perlite, for example.

That said, stuff like lava rock, being as jagged as it is, tends to get “hung up” before having an opportunity to settle, so I’m sure that keeps it more open than it could be.
 

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