Pot in pot semihydro?

[Grim Tuesday]

I am a total beginner, and have been reading about semi-hydro and am thinking that I would like to try it out for plants that seem suited to it (i.e. as far as I can tell, intermediate or cool growing, generally moisture loving plants). I live in the northeast USA and have a furnace on in the winter and air conditioning in the summer. In a word, it is dry. I have successfully been growing Phalaenopsis for a few years and I bought some more interesting and complex plants a few months ago (miltoniopsis nakamoto, dendrobium tobanese, and after congratulating myself on keeping them alive and growing for at least six months, last week I bought an assortment of seedlings from LA Orchid Connection and Olympic Orchids, which I am now waiting for the weather to permit shipping and delivery). My plants are currently growing on windowsills supplemented by LED shoplights (Monios). I want to try semi-hydro, especially for the plants that seem they will like it and are further away from the sink.

But I want to be careful about my low humidity. I read the whole thread on humidity trays, so they seem out. But what about hyper local humidity? I see the standard method of semi-hydro is the pot with two holes on the side. But does anyone use a pot-in-pot method where the inner pot is a LECA filled standard orchid pot with holes in the bottom, and the external pot is a 16 oz takeout container (at least for 2"- 4" inner pots)? Water would be filled up to a line in the outer pot and the holes in the inner pot should allow the water to reach up to the same level in the inner as outer. Theoretically the local evaporation of water from the external reservoir area should cause some higher humidity and perhaps influence the overall evaporation of water and the dry line location, especially if the top of the inner pot is below the height of the outer pot. It could also theoretically allow for longer time between flushing, as there is a larger water reservoir to absorb water from and would take longer to become concentrated with waste products. It would also allow me to test different reservoir levels for my house and see where the dry line falls in different seasons.

Other than "has anyone tried this before and can steer me as to if it's a good or bad idea" I have a few specific questions:

- I am imagining watering would take place by removing the external reservoir, dumping it, then refilling it up to a line and putting the internal pot back in. This removes almost all the old water, like the standard method, so I don't think it is just "topping up". But it doesn't quite flush the upper layers like the standard method does by filling to the top and draining down. Is this Super Bad or Probably OK?

- Is humidity mostly important to the root zone (and particularly the dry line in semi-hydro) or is it mostly a leaf thing? If it's for the leaves, then this probably won't change anything. But if it's about the roots and the dry line then this seems like it could move the needle.

- With a pot-in-pot method like this would slitted pots be better or just regular plastic pots with holes on the bottom?

[fishmom]

Hi Grim, and welcome!
I suspect that by using your suggested method you will see white salt deposits begin to form on the top surface of the LECA in the pot containing the plant. In time this makes a barrier for new roots growing down into the medium.

[Grim Tuesday]

I can totally imagine that happening. Do you think I could fix that by filling the reservoir by watering into the internal pot to wash those down?

[WaterWitchin]

First, Welcome to Orchid Board!

What is your average humidity percentage in summer and winter? If you don't have a temp/humidity gauge, get one.
Here's the last one I purchased, and I like it. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

When starting out, one thing that makes life easier is researching and buying orchids that are already within your environment parameters or can be easily tweaked. Don't just buy an orchid because you think it's cool. First, get experience under your belt by getting orchids you can have success with in your particular environment and under your care. You may have already done this before you ordered your latest go-round of plants, but it's worth saying anyway.

When you commence semihydro (SH) try to move them into SH when their roots are in active growth. Better success. Save just potting them up in SH until you have more experience under your belt growing them that way.

Yes, some orchids lend more easily to SH, but one can actually grow just about any orchid DEPENDING on one's environment and culture. An orchid I grow in SH may not work well for someone else, and vice-versa, even though both individuals have lots of experience with it.

Yes, some folks do SH in a two-pot system. I don't like it for many reasons. The main reason is mechanics. I don't have time to manually pick up each pot, depot it, dump the water, water orchid, then sit back into the pot and refill the reservoir. Too time consuming if you have many plants.

The second is that folks tend to do just what you're saying. Dump the reservoir, then refill the reservoir and plop the plant back in. That's not how SH works well. The whole idea is regular flushing. It isn't just replacing lost water... when you flush the water is going from the top through to the bottom. That brings air through the LECA is also refreshing the environment of the pot by pulling through air on its way down and out. So if you choose that system, you'll need to dump the reservoir, flush a copious amount of water through the inner pot, then replace water in reservoir and stick inside pot back in. So that answers your question toward the bottom... no, it isn't good to not flush water through the LECA. How would that get rid of rotted roots in the pot while it's transitioning? How would that get rid of the mineral buildup throughout the LECA in the pot?

Humidity is important for the whole plant, not just parts of it. A 40-60% RH will be adequate for MOST orchids you should be attempting when starting out. Air flow is also important as you get the humidity higher. A pot inside a pot isn't going to really do much humidity-wise.

There are lots of ways to avoid a dry line that's too low. The reason for using an in-pot reservoir are for ease in numbers, correct flushing, and less mechanics.

I grow almost everything in SH and have for a long time. There are other members here who also grow in SH, and I'm sure will chime in.

Ask away with any questions you may have.

[estación seca]

Welcome!

I agree with WW and fishmom. Flushing is a major component of S/H. I grow a lot of plants in S/H. With your proposed potting system I would water by removing the inner pot, watering it thoroughly at a sink or bucket, letting it drain, dumping the old water from the outer pot, rinsing that pot in the sink, putting the inner pot back in the outer pot, then adding water to the desired level. S/H is a bit of work if you grow plants where you don't want a wet floor.

Don't rule out warmer growing plants in S/H in a home. It will depend on your room temperature.

Humidity is very important for many orchids and less important for others. A humidifier pointed at your plants will help. I would suggest learning to grow plants tolerating lower humidity before deciding how to increase humidity. Many phals with rounded, white to pink flowers do well in lower humidity; the ones with star-shaped yellow to red to pink flowers don't. Many Cattleyas also do well on windowsills, though most people in northern areas need to use extra electric lighting in winter to get them to flower. Many Oncidium hybrids are also good growers in homes. Dendrobiums with ancestors in the Den. phal group do well in homes, as well as Latouria Dens.

[Ray]

As the person who pretty much “invented” S/H culture for orchids, I arguably have more experience than anyone.

1) Any plant can be grown in S/H culture, but that does not mean anyone can grow any plant that way, because “inert media” and “water delivery” are only two, minor aspects of everything that constitutes orchid culture.

2) As my learned colleagues have stated, the watering method you described is insufficient, and is exactly why I invented the “two holes in the sidewall” design to replace the pot-in-pot. Don’t get me wrong - it works fine, but having to disassemble, dump, flush, reassemble, and refill (with the possibility of overfilling and drowning the roots) is just too big of a PITA with a greenhouse full of plants, so “flood and forget” (k owing you cannot overdo it) worked a lot better. I have grown houseplants quite successfully in the p-i-p containers.

[Fuerte Rav]

I do Pot in Pot S/H - it works for me. I have about 30 'grocery store' phals, some large and some small. It is a bit of a pain doing the disassemble, flush etc but just about workable with my numbers. It takes approx 25L of mix to do all of mine. I use the mix for flushing as well as refilling the reservoir level. (mix is either plain water, dilute fertiliser, Kelpak or CalMag. Repeat pattern ad infinitum.) My RH is around 45% all year apart from an odd occasion. I fully flush at least once a week in Winter and at least twice in Summer.
The bonus is all the mix gets used afterwards for seedlings and plants in my garden.
As I say, it works for me in my conditions and does mean I can easily leave my plants for a week without any worries if I need to go away. If I'm away for 2 weeks my plant sitter has instructions just to pour so many ml of plain water on top of the leca, avoiding the leaves - makes it easy for her - she doesn't need to flush etc - one week without flushing won't hurt.

Good luck!

[Dusty Ol' Man]

Pictured are two s/h methods that are being discussed. The pot in pot was used because at the time I didn't have a container of sufficient size for the plant and I wanted to get it into something. It has stayed there and is forming its second of two new growths. I only have this one in this culture so care takes little time. I use rainwater, so salt buildup is nonexistent.
The other pot is the two hole, internal reservoir setup Ray was talking about. Again, I have few plants, so care twice a week takes 30 minutes. Oncidiums and cattleyas seem to like the culture.

[Grim Tuesday]

Very interesting, thank you all so far for the info! I had been under the incorrect assumption that the primary purpose of flushing was to completely exchange the water in the pot, rather than the mechanical rinse of the roots. The advantages of the full rinse do seem very clear once I think about the mechanism of it.

In that case, the pot-in-pot seems to be adding work (though, less added work ratio for someone like me who hopes to have 20 plants and a kitchen sink than to someone with a whole greenhouse and floor you can drip water onto). Does it actually manifest any benefits (time between flushing, local humidity)? Ray have you grown both ways indoors? Does one of them have an advantage?

[Louis_W]

I can't add much to all the SH feedback but I can chime in on the humidity issue. I live in New Mexico and my humidity is usually around 10% and I'd say it pretty rarely gets above 30%. Sounds fatal doesn't it? I do strive to get that nember higher and I'm not saying it doesn't matter but so far I have had no issues growing. Rays recommended SH culture works great and it makes it easy for you to succeed. I highly recommend you try it.