Semi-Hydroponic (S/H) Setups

Slippertalk Orchid Forum

Help Support Slippertalk Orchid Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


ST Supporter
Supporting Member
Oct 25, 2015
Reaction score
Hello, I am looking to modify/change my orchid watering regime.

I am looking for advice and suggestions on how to install a semi-hydroponic (S/H, passive hydroponic) system.

I've been reading/searching the forum and came across this post by baodai (// that closely resembles what I would like to do.

I travel a lot, plus it is tricky to get the RO water close to where the plants are being grown. For these two reasons (and a few others) I was thinking of using my 50gl drum as my reservoir of RO water (which may need to be filled once a month or so) and have it feed to the plants and ensuring a constant level of water is at the base of each pot. I came across this website of a similar idea, was wondering if anyone had any experience:

I would like to know the best way to have the water in the reservoir maintain a constant level of water in each plant that doesn't require a pump or an electrical timer.

Additional questions:

Does S/H system work well for seedling paphs that are hardened but still too small to be in a individual pot?

Any other things I should consider before implementing this type of irrigation system? I read how one needs to be careful about salt build up and periodic "flushing" of the pot/media may be required.

I am about as useful as a bucket with holes when it comes to building stuff or DIY projects, but I appreciate any advice on how to best approach this.

I believe you're trying to "overthink" this.

I invented the orchid-growing technique specifically because I traveled a great deal - 5 or 6 days a week, occasionally two weeks straight - for several years. If you use the "converted deli container" pot design, and water it properly (flooding the pot at every watering, and letting it drain), the vast majority of plants can do well with watering once a week, and it usually isn't an issue if you let it go for two.

Trying to find a way to automatically keep the reservoir at a constant level will require some powered device and actually sets you up for issues down the road.

Evaporation of water is from the top of the medium. Water being brought upward by the clay medium carries nutrients and plant wastes with it, so they are concentrated near the top as the water evaporates. Keep up a steady supply from the bottom and that just builds and builds, eventually reaching a point of toxicity. "Periodic" or "occasional" flushing doesn't do sh*t to remove it. (Folks who only "top up" the reservoirs will tell you what an issue that can be.)

Ideally, you want the LECA pellets to be moist all the way to the top, because as long as there is still liquid solvent (water), there is no precipitation and buildup. (Not truly "none", but it's minimal, and much more easily flushed away by proper watering.)

Focus your thinking on raising the humidity in the growing area to slow the evaporation rate, use the pots with the two holes in sidewall, water them properly whenever you have the opportunity, and your plants will do much better.

Thanks Ray, from my searching/reading through the forum of this subject I know you have a lot of expertise and I was looking forward to your reply.

You don't think a reservoir is a good idea and that even periodic flushing won't eliminate the salt (and plant residue) problem. This is a bit of a bummer for me, but I trust your experience.

I noticed a lot of users here are growing via ebb & flow system. Is this in principle, the same system as S/H? How do they manage the salt issue?

My house water as a water softener. Moreover, the connection of my water sprocket where I connect my RO system is a bit away from where the plants are. Filling up a watering can each week directly from the RO system is a big hassle. I was hoping to fill the 50gal drum, add the appropriate fert mix once every couple of months. I guess I can still do this, then hand-fill the watering can from the 50gal drum each week when I need to water the plants. Though this will be somewhat of a pain when the water level in the drum is very low.

Anyways, I am already thinking of ways to overcome this. Thanks for your advice again.

FYI, I found it a bit of a chore searching for S/H topics on here, mainly because "S/H" is too general and generated too many hits. Below are some forum threads I found helpful, I hope it will be useful for others:
Ebb and flow is active hydroponics. In those setups, the entire container is typically flooded and drained at each, rather frequent cycle, which flushes and keeps the medium moist, rather than just keeping a certain reservoir level, as in your original proposal.

One more thing to consider about a common reservoir or complete bath as in ebb and flow: that shared irrigation source is also the ideal way to share pathogens!
Hi, I'm slowly experimenting with semi hydroponic growing in some of my paphs and so far everything seems to be doing well (ie they haven't died yet!) ,.

Question, has anyone experimented with putting paph compots in a semi hydro setup? I suppose it would be tricky doing it right out of flask due to the flask medium unless one washed and separated the plants immediately (which some people do anyways).

If s/h compots dont work, at which point is it safe to move a young plant to a s/h system? In other words, how big of a plant should it be?
I have put ex-flask seedlings into S/H culture with great success.

You may either separate them and pot them up, or just put the block of agar on top of the LECA and fill in around it. With normal watering, as the agar dissolves and washes away, just drop in a few pellets to fill the voids and away you go.