Yeah, there is not alot of info about growing houseplants in Semi Hydro.To answer your questions;
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1. One of the disadvantages of semi-hydro is the need for relatively frequent watering. I grow inside where it's dry in the winter with humidity at ~35% or even lower sometimes. Considering trying some hoyas in semi-hydro (either rooting cuttings or growing or both) - they do not like soggy feet but most should not dry out completely either. How often will I likely need to water?

* How do you figure? You don't water more often, in fact you can usually water much less often. Some of my S-H plants do fine getting watered every 3 to 4 weeks as long as I make sure that all the water has been changed in the reservoir so there's no mineral buildup.

I haven't had Hoyas in years so I won't comment on them except to say that if I got one I would try it. Just make sure the container is 4-6 inches deep and the water level is 1 inch or less so there is much air at the root zone. There are many plants that require dry conditions that will thrive in semi-hydro.
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2. My medium for most plants right now is the gritty mix by Al in Container Gardening forum. He says (and it makes sense to me) that it is already very close to semi-hydro method: very chunky and superb drainage, can't really over-water no matter how hard you try. But there is no standing water at the bottom - instead the mix itself retains some water for the roots to use until next watering, just like regular pots, only with much more air. How does semi-hydro growing compare to gritty mix? Am I likely to see any improvement at all or is "perfect the enemy of the good" here? Has anyone done experiments for gritty mix vs semi-hydro? (controlling for the other factors, of course).

* I've never used the Gritty mix as is often listed here but I've used other very loose quick draining mix recipes for growing medium. With these media what you have is basically a “drain to waste” system so you mix up a batch of nutrient rich water and pour it through the pot and maybe 90-95% or more is then poured down the drain or out in the yard or whatever and is wasted. Whether or not you see improvement depends on many factors, I can say that the plants I've grow in semi-hydro have done very well.
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3. How come roots do not rot in that bottom inch of standing water? If they do not grow in there, what's stopping them? Can they be water roots rather than soil roots? How is THAT possible - they have to start as soil roots because they start in soil up above. Can a root become "water root" half-way down its length? Major confusion here.

* They do grow down into the water, As long as the water don't become over saturated with minerals they don't die off any faster then any other roots. Since there is no soil in the pot I believe all the roots in the pot can be considered as water roots. I do think the roots can transform in structure as become longer and grow into a different environment but I don't know for sure.
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4. I have not seen opinions on how different s-h media differ from one another other that to say things like "I like Hydroton more than Growstone" without really saying why. I would think that because Growstone has more flat(ish) surfaces, the wicking action will be better than with hydroton because there is more surface contact between the particles. Growstone also has more visible pores, so water retention also looks better than smoother looking Hydroton (although it has micro-pores, I understand). Apart from this general understanding of physics here, I do not really know what I am talking about, so would appreciate opinions on this. What is your favorite s-h medium and why?

* In the GardenWeb Hydroponics forum there has been many threads about different media. I mostly use Hydroton but I've also used long fibered sphagnum, perlite and chunks of charcoal all with fine results, not mixed, each by themselves. I did find that Sphagnum starts to breaks down after a few years but I got good growth using it. Perlite floats so I had a few inches of it in a large glass container floating on top of the water. Great for cuttings and plants tied to something to hold them up. Charcoal starts out with a higher ph but it drops with use.

It seems that other than the wicking capacity, you also need to consider the ph of the media for example, rockwool can have a higher ph then hydroton. From what I've read, The shape of the clay stones is a matter of opinion but I haven't tried other brands so I've never compared them. Seems to me that flatter stones would mean less space for air.
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Finally, 5. Just generally, what kinds of plants /growers /environments is semi-hydro better than gritty mix or 511 mix (another one of Al's mixes I use, generally for more moisture-loving plants)?

* Again, I've never used gritty mix so I don't know.
I have grown various species of Philodendrons several Anthuriums, Orchids, Pineapple, Schefflera, Tacca, epiphyte cactus, Begonia , Dracaena and others in semi-hydro and I've seen photos of terrestrial cactus being grown this way too.

This post was edited by dellis326 on Sat, Feb 8, 14 at 12:09

Dellis gave you a lot of good answers. I have just started using semi hydro so I can't add much to it.
So far I do not feel that it makes watering more of a burden. If you don't want to water as much, you could just use a larger water resevoir. :)

Based on what I have read about semi hydro, it seems just about any plant that can be rooted in water will do well in semi hydro. I know that people on the Hoya forum do use it for hoyas with success.

This post was edited by summersunshine on Sat, Feb 8, 14 at 9:35

i don't do semi-hydro except in perlite for rooting when there's no roots at all. so the plant grows 'water-roots' all the way thru perlite into water. i add 1tb 3% peroxide to 1 gal of water - that prevents water going stale AND keep roots clean. then i xfer into 50% perlite soiles mix on water-wick, same roots keep going.

as far as soil-roots /water-roots. many plants have both: they send out water roots deep into the ground. many tropicals survive dry season that way, even if they shed the leaves they still get water for the roots.
so they can co-exist. but that does not answer the question how they transition into hydro. most people just clean the 'soil' roots in water and plop them into hydro. the plants obviously do not die. there's a whole industry going. if they were not successful it would not happen ;).

i have a lot of my plants on sub-irrigation: roots in soiles mix with 50% perlite for wicking and water-wick dropped in water-reservoir. most plants grow water roots along the wick into the water. roots decay overtime - i chop them off and within a couple of weeks they regrow fresh ones.
a lot of SIP containers have mesh on the bottom of the inner pot: an inch of air below prevents roots from growing into water. supposedly ;). i have orchid pots perforated all around the bottom and still roots go thru and into the water! the humidity lever is very hi between the inner pot and the water surface: roots just love it!
but i use reg pots, not meshed ones, so my soil roots are contained physically in the upper pot - but for example for ficuses it's the tap root that extends into water - same tap root that grows in the soil above.
so it obviously handles both soil and water.
look at lechuza write-ups: it's a SIP with specialized clay-aggregate for roots to grow in: so it's like quarter-hydro :). it's been around for 10 years at least. you might get some answers to your questions .

the water consumption for semi-hydro AND SIP containers is much much less then for top watering.
the plants consume only what water they need. the medium stays drier, it's never wet or water-logged.
all moisture loving plants (evenly moist but not wet: a lot of tropicals fall into that category) are great in hydro/sip with very little effort.
also plants that die/go dormant if totally dry like hydro/SIP a lot. lots of tropicals again (dry season=dormancy).

This post was edited by petrushka on Sat, Feb 8, 14 at 12:03

Just to clairfy something I said above;

I said "I do think the roots can transform in structure as become longer and grow into a different environment "

I do not mean that they actually change form as conditions change. I meant that if roots growing through soil grow out into water they will from that point grow as water roots, not the whole root changing. Soil grown roots will likely die off when put in water for any length of time.

It is usually recommended that you prune off many of the roots when transferring a soil grown plant to semi-hydro.

Thanks for your answers, everybody.

I've read in multiple places online that watering is more frequent with semi-hydro than with traditional mixes, even fast-draining ones. Ray Barkalow, the inventor of semi-hydro, and Doug of vermonthoyas.com both talked about it. I am surprised you water every 3-4 weeks, Dellis, and that you say water consumption with semi-hydro is lower, Petrushka. I would think the need to drown the pots when watering and evaporation off the top layer will increase the watering needs. It gives me more of an incentive and interest to just try and decide on my own when advice is so different.

so i looked up ray - and on the first non-ray site mentioning him got 'Watering is required much less often than in a traditional set up.' ;).
you see, IF your pot has only 1" of water 'reservoir' at the bottom = true, it's not much, it won't last long.
BUT! if you have more...a LOT more ...you're only limited by the size of your reservoir.
the aggregate only needs 'not to be dry' to continue wicking moisture upward. once you drench it and it fully absorbs water - it'll stay moist for a long time.
also the very top layer that dries up faster acts as a sort of mulch - to reduce evaporation.
what i do on top of that is put a 1/2" aquarium gravel on top. i read that it completely blocks evaporation. so i need even less water (when i am trying to make it last longer...like 2mo ;)).
however, top evaporation will increase humidity - so it can be good, if that's what you are looking for.
so periodically you have to top water to remoisten aggregate, but not THAT often to be sure.
why i don't do semi-hydro forevermore? it's handling water containers that is problematic: stuff splashes and no matter what precautions i take, i have to crawl and wipe (damage to floors is not a joke). also a lot of my stuff is on hi/shelves so hoisting water up is not very easy, especially on step ladder...
best if it's low on tiled floor, which i don't have in the rooms. so i only use it for small plants interim.
AND large qty of water is heavy too.
also as water reservoir increases you need a higher shelf interspace to accommodate it - i have to maximize my shelves to the limit, so can only use pint-size containers, unless i am going away for an extended time.

greentoe,

1) watering frequency... al has said over and over on this forum that he waters according to his plants' needs, and that this is often around every three days. ray barkalow recommends watering once a week, or at a minimum every 14 days, even if a particular plant still has water in its reservoir. this means watering one half to one quarter as often. if you are seeing information from ray that conflicts with this, please post some links, because this is what i remember from reading his websites and orchid forum posts years ago.

2) dan's watering frequency... the critical thing in semi-hydro is keeping a nutrient water source in the bottom of the grow pot. the media needs to stay damp. however, this level needs to be relatively low in the pot so that there is still plenty of 'airy' media above the water for the plant to grow its roots. this water level should be about a fifth the height of the grow pot. it is NOT ok to add water above this line to try to reduce your watering frequency... but it IS ok to add a wider water tray for the grow pot to sit in. the larger tray can hold a larger volume of water, and so you can reduce your watering frequency. just be sure to only ever have a water level height at the proper place.

in my case, i set my plants in saucers that are only a tad bigger than the grow pot. these saucers will hold enough water for about a week and a half or so. but, when i travel, i move the plant, in its grow pot, to partly covered trays that hold a much larger volume of water. 6" pots go into those disposable salad boxes with a hole cut in the top to accommodate the pot. and the large pots 10+" go into 12" by 18" plastic trays i found in the organizer section of a big box store. i loosely cover the top with painter's plastic to cut down on evaporation. then i fill them with water/nutrients to the same 1" for small plants or 2" for large plants as i usually do with the smaller trays. with this set up, my plants can easily go 3 to 4+ weeks before they need watering again.

the reason i don't leave my plants like this all the time is that ray, and many other semi-hydro folks, including companies who manufacture the media, believe that most plants are healthier with a water level that rises and falls more frequently... such as every week or two. the idea is that a falling water level will pull oxygen into the root zone. a few of my plants, such as some Homalomena "Emerald Gem"s, could care less, but a few of my variegated Aglaonemas lost some of their good looks during a 1 to 2 year period when i was away from the house a lot, and they remained in the 'vacation' trays most of the time. none of them died or anything... but their leaf color was faded looking. they bounced back when moved back into their normal trays.

3) evaporation... remember that most of what ray has written concerns his method for growing orchids in a humid greenhouse. in a dry, indoor home, surface evaporation will be much greater. however, as mentioned earlier, the media surface will dry and act as a kind of mulch of sorts. i, like petrushka, have begun to add a 1/2" or so layer of gravel to the surface of the hydroton. it sounds like my gravel may be a bit larger than hers, but it will work the same. the kind i use is sold as a decorative polished gravel and the pieces are about the size of the hydroton. now, in my case, i'm not doing this to reduce watering frequency (and it won't change it much, if it all). i'm doing it because i think it looks nicer... and most importantly, to help reduce salt accumulation in the media. salt deposits at sites of evaporation, and reducing evaporation will therefore reduce salt deposition. even with this, i still flush all my pots in the shower, or outdoors, every 3 months at least.

4) watering volume... if you read and follow rays watering instructions, you will burn through a LOT of water. his watering instructions are to fill the grow cups (that have two small holes about an inch up from the bottom) to the top with a running stream of nutrient water, and then let the excess drain out through the holes. his plants are beautiful and he has been doing this for years. so his method works. however, to me, this seems like such a waste of water. also, if you search for forum posts where ray talks about his own indoor houseplants, he doesn't water the same way. he merely waters until he has a little flow out of the overflow holes... and then every month or two, he takes the pots to the sink and gives them a good flush with water to prevent salt accumulation. he said that this seems good enough for most house plants. he believes that they aren't as salt sensitive as some orchids. also, houseplants are growing and respiring at a much lower rate than actively growing plants in a much higher light greenhouse.

5) as for 'water roots' versus 'air roots' and such... the short answer is that as dan and petrushka mentioned above, roots will grow down into the water. what you don't want to do is drown the "air roots" by raising the water level too high. they're not used to this. also, for most of my plants (primarily aglaonemas), their soil roots survived the move to S/H just fine. very, very few roots died during the transition. most of the time i don't even tent the plants (though i did water the media more frequently to keep it a bit damper than normal. thinner leaved plants would likely appreciate a little extra humidity though.

6) how i water... first, i never let my plants go dry. if i see a tray that's empty or very low, i usually water all of the plants so that i can forget all of them until next time to water. i don't walk around every two or three days checking on how 'everyone' is doing. when i water, i dump out any remaining nutrient water in the water tray, and then re-fill to the proper water level with fresh solution. never, ever just "top up" your remaining water to the proper level because salts will accumulate. and, as i said, flush with plain water from time to time as well. oh, and i place a piece of blue tape with the level marked on the outside of the drip tray in case anyone else ever needs to water my plants for me. if someone else is watering, this is the only time i 'top up'. i just tell them to water until the water is up to the line. easy, peasy. even a 5th grader can water my plants now.

for feeding and watering my plants, i add 1 tsp of Dyna Grow Foliage Pro 9-3-6 to 1 gallon of water. i just use tap water, which here in portland or, is pretty decent tap water. i don't adjust pH or anything. our water is very soft, and a bit on the acidic side. folks who live in areas with hard water will likely accumulate minerals on their ceramic media faster. you might want to try to water with rain water or distilled water instead. you also might be fine as long as you're even more careful about flushing. well, and a gravel top dress might help as well.

do NOT use softened water on your s/h plants.

i hope some of this helps. i really like this method of growing houseplants. it takes the guess work out of watering...

cheers,

nancy

great write-up, nancy!
i have a question about your vacation trays.
when you set up larger pots in big trays, you submerge 2" of the bigger grow pots into the liquid? on some kind of support? or is it that they sit on the bottom of the tray that you fill up 2" with liquid? but then you don't use the pots with 1" hole above the bottom? but some kind of mesh bottom pot? otherwise it won't be able to use all the water in the tray long term? or am i misunderstanding smth?
did you ever try to use another reservoir with a tube, to get the water xfer going between the two reservoirs, to supply extra water so to speak? without the pump or valve? or is it a very far fetched idea?

This post was edited by petrushka on Wed, Feb 12, 14 at 10:20

petrushka,

i use regular plastic houseplant pots that have a single drainage hole in the bottom. i usually lay a piece of fiberglass window screen over the hole so that the hydroton can't fall out or get stuck in the hole. because the hole is in the bottom, you can change it easily from one reservoir tray to another. i do try to keep my grow pots that are used to 1" of water depth in 1" water depth, and my 2" depth pots in 2" of depth (i hope that this makes sense). theoretically, you could have a storage bottle - like they use for pet waterers - to keep the reservoir topped up to some level, but i've never done that. my 'vacation' trays can hold quite a bit of solution, so i haven't tried to increase this, though it's probably possible.

cheers,

nancy

ps in the link below, they call my method "pot and saucer". i don't use the special water level indicators...

i'd like to figure out a way to make my set-up a little more decorative, but for now, i'm just happy that my plants are happy.

pps i have tried growing plants very similarly to what you're doing. i had trouble with the media being so light (the perlite), that the whole thing would tip over and make a humongous mess. but the plants were happy. i'm glad that it's working for you.

Here is a link that might be useful: Houseplant Hydroculture

got it nancy, thanks.
i looked at your link - loved the instruction on how to set up a DIY water-gauge with a straw ;). gotta to try that next.
i do smth weird too: it's a mash-up of hydro and sip.
i make a little cone with coir fibre matting (like for baskets) fill it with perlite and stick a thick wick on the outside of coir, dropping into water. that goes into the pot with wick trailing. coir helps to wet all around and holds it together. i can even xfer it to a diff pot easily.
sometimes i put the bottom in water more often it's just on the wick, especially if i want to keep it on the drier side.
so it's wicked hydro. pun intended :).

To put it even shorter, roots adapt to the environment in which they grow, AS they grow.

Thanks for the replies, all. Interesting link, Nancy.

>> ray barkalow recommends watering once a week, or at a minimum every 14 days, even if a particular plant still has water in its reservoir. this means watering one half to one quarter as often. if you are seeing information from ray that conflicts with this, please post some links, because this is what i remember from reading his websites and orchid forum posts years ago.

You remember wrong, sorry. Here is the first link I found (copy to browser, remove space and press enter):

http://www.first rays.com/forum/viewtopic.php?f=5&t=294
"I think the important parameters in any automated watering design is the ability to rapidly fill the pots, so there is sufficient flooding and flushing action. The other alternative would be to water at a slower pace, but to do so very frequently - 1 or 2x per day - to simulate a steady flow through the pot to take away wastes and prevent the buildup of residues."

And here is somebody else to show you that there is contradictory advice, not just from Ray and Doug advising daily watering:
http://forums.gardenweb.com/forums/load/hoya/msg0820135130989.html
"Be sure to water every day//every other day if you're in semi hydro."

>> evaporation... remember that most of what ray has written concerns his method for growing orchids in a humid greenhouse. in a dry, indoor home, surface evaporation will be much greater.

Exactly my concern. If Ray in his humid environment suggest watering daily, then it's gotta be more often or at least as often in drier environments. But I hear you all and will see for myself how this works. My Growstones order is on the way.

I like the idea of top dressing with something that slows evaporation you both suggest. I've heard also the idea of top dressing with long sphagnum. Anything that does not fall to the bottom and gunk up the pot, I guess.

>> watering volume... if you read and follow rays watering instructions, you will burn through a LOT of water.

Yeah. I get it that he wants to make sure to wet all surfaces of all particles, but it seems so inefficient to flood the whole pot for that. I think a wide gentle spray from a little shower-type attachment I use from a couple directions will be fine.

LOL at "wicked hydro". :-)

greentoe,

thank you for posting the links that you have been referring to. now i see why you are so confused.

the first link you posted, where ray is saying something about daily watering... is referring to an automated watering system for a greenhouse. in a greenhouse, the conditions are completely different than in a home. house plants usually grow in much dimmer light and need much less water as a result. even adding supplementary lighting will result in growth and watering needs that are dramatically less than in a greenhouse.

the second link you provided concerns rooting hoyas. conditions necessary to root an un-rooted cutting are (again) very different from those needed for a typical houseplant with a good root system. cuttings need extremely high humidity and moisture right up next to the stem. in a typical semi-hydro pot, in a home, the top layer will be too dry without some sort of tenting or very frequent watering. adult house plants don't need this treatment.

>>evaporation

when ray says that frequent watering in a greenhouse is good for the plants... it's not because they are "drying out" so fast from evaporation. they are 'drying out' because they are growing so fast. and, more importantly, the frequent 'watering' keeps the nutrient reservoir near it's ideal levels for the plants. actively growing plants burn through certain nutrients faster than others, and they dump waste products into the root zone. flushing with new nutrient solution cleans all this up and restores the balance.

in a home, the evaporation will be higher - due to much lower humidity levels - but plant growth will much, much slower.

if you go over to the link below, and search for threads about houseplants, you will find some comments from ray about how he grows his houseplants. he doesn't say exactly how often he waters them... but says that it is much less often. also, he takes the smaller ones to the sink about quarterly to flush them well with water. he also only waters from the top, just until nutrient solution begins to overflow out of the holes an inch or two up from the bottom. for some large planters, he only 'feeds' them every other month and only 'waters' the rest of the time with tap water. these planters only get flushed once a year outdoors with a garden hose.

as far as a can tell, he doesn't cover the surface of the ceramic media to reduce evaporation.

i hope this helps.

i think that as long as you don't make some of the mistakes i made... such as continually topping up with nutrient solution and not flushing the pots from time to time, you'll be fine. also, don't let the pots completely dry out. do let the nutrient level fall on a regular basis (ie don't top up the pots every day) so that oxygen is sucked into the root zone.

most houseplants should easily be able to go one to two weeks or more between waterings depending on the size of plant, size of pot, volume of nutrient reservoir, etc.

oh, and with any significant change to your culture method, try practicing with a few sacrifice plants in case something doesn't work out. in converting all my plants to s/h i think i only lost two. i have had a few that took longer than others to adjust... and a couple that needed a bit lower light level than when they were grown in a peat type mix. but other than that, it has worked well for me.

cheers,

nancy

Here is a link that might be useful: orchidboard semi-hydro threads

Thanks, Nancy. My growstones are here, and I am looking forward to rooting and growing in them semi-hydro.