Quasi-hydroponics for Phragmipedium

For some Phrag species and many Phrag hybrids, the best way to grow healthy orchids is with hydroponic culture. Here, quasi-hydroponic simply means that the phrags sit in shallow, moving water for a certain amount of time each day.

Many people end up drying out their phrags too much, or at least don't allow them to realize their potential, because they believe that a hydroponic system would be too expensive or too difficult to make. Others fear the possibilities of root rot from fungus or bacteria that may result from the practice of growing orchids in or near the standing water of a traditional "semi-hydroponic" setup.

I found that building a small quasi-hydroponic setup was very inexpensive, relatively quick, and really quite easy. These are some basic instructions for how to reproduce the first style I made, which was by far the easiest and cheapest.

PLEASE NOTE: Other orchid enthusiasts use these term differently. They will use the term "semi-hydroponic" when they pot their orchids in hydroponic medium (usually Hydraton or PrimeAgra) and then water it heavily or pot it in a vessel with no drainage in the bottom inch or two (which acts as a reservoir). I neither condemn nor condone the more common semi-hydro method, I simply want to make clear that it is not what I'm advocating here. Others may call this my method simply "hydroponic", but since the roots are not submerged in water or nutrient emulsion in my method, I think the distinction is fair.

The trays in this system are constructed out of steel alloy framing-stud material, found with the lumber at building supply stores. In fact, I don't really know exactly what they are intended to be used for. They come in 10 foot lengths in a couple of different sizes. The one I started with was the 2x4 size (like the lumber, these are actually 1.5 x 3.5), and it cost about $3.50 -$4.00 at Home Depot. I thought that 1.5 inches deep would be sufficient to hold about 3/4" of running water, and it seems to work fine. There is also a 4 x 4 size, which may be better if you'd like to run deeper water, but it is more restrictive of the pots that will fit inside.

I was initially concerned about using the steel as a building material, since some mineral content from it might be picked up by the water running across it. Before I started using it to grow in, ran water through it for a week (RO/DI) and then tested the water to see what it had picked up. The differences in my readings were negligable, so I've stuck with it.

However, if you're not comfortable with steel, other materials are available, and would require only minor modification of this plan. I've considered vinyl and aluminum gutter materials, and various other materials I've seen at the hardware store. I'll leave that up to you.

The first step in the process is to cut your piece of tray material to the desired length +4 inches. [I'm going to assume that you're using all of the proper safety precautions and won't pester you too much, but your really should wear safety glasses, and some good leather gloves. Metal is sharp!] Since I was growing in front of a window that was four feet wide when I built my first one, I cut it down to 52" (48+4).

The next step is to close off the ends. This is done by cutting slits down the corners of the tray and then folding the resulting flaps in, like the end of a box. Cut 2" along the corner (the right angle where the tray bottom meets the side) of the tray on each side. This can be done with a hack saw (works well, but it's slow) or a reciprocating saw if you have one. I imagine that heavy duty tin-snips might do the job too, but I've never tried it.

When this is done, fold the bottom of the tray up where the two slits end. It would also work if you folded in the sides first, but the design is more water-tight if you fold up the bottom instead. Once the bottom is folded up, the two sides can be folded in behind it.

At this point, your end should appear nearly closed off, but the end of the bottom part of the tray that has been folded up should be about a half inch higher than the sides of the tray. Use a pair of pliers to fold it down over the sides that are folded in, clamping them in place. The ends can then be sealed in the corners with a bit of silicone. Here I recommend using a good quality silicone rather than a cheaper caulk, I've had bad luck with it. A little duct tape can cover the sharp edges on the exterior.

The interior of the ends will look like this when all of the folding is done. Done in this order, only the vertical corners will need to be sealed with silicone or epoxy.
This photo shows the finished end from the exterior, also illustrating the sequence of folds. Clearly shown is the material folded down over the top of the folded-in sides. As you can see, this leaves sharp edges which can be dangerous for any person or plant that rubs up against it. Usually, I cover the end with a couple of layers of duct tape, just to keep from getting snagged.
With that accomplished, you have a complete, sealed tray. The only difficult part left is to make the drainage system.

To begin with, choose an end that you'd like to put the drainage hole in. The drain will be in the bottom rather than the end or one of the sides so that all of the water can drain. Most phrags don't mind a little standing water, but it decreases your risk of bacterial infections if you build it such that the water drains completely when it is not running. Make a mark with a permanent marker about 1-2 inches in from the end in the center of the tray. This is where you will eventually drill a hole. Place the tray on top of a solid surface with a hole in the middle (I use a large roll of duct tape ) so that the dot you just made is centered over the middle of the hole in the tape. Finally, use a ball-peen hammer to beat an indentation where you made the dot. It doesn't have to be too deep, 1/8 - 1/4" is easy and works well.

After the tray has been beaten, it is time to drill the drainage hole. The size of the hole you drill will depend on several factors, but pimarily the size of the hose that will go from your pump into the tray. Mine is 1/2", but yours will most likely be different. Since the pump may be able to push water into the tray faster than gravity will pull it out, it's a good idea to make the drainage hole a little bigger than your hose.

Perhaps the best thing to do is to make them the same size (then you only have to buy one size of tubing), and put a valve in the input line. Hardware stores usually sell in-line valves for drip-watering systems (in the sprinkler section). I bought one with 1/2" barbed hose connectors on both sides for about $1.50. Then you can adjust the flow of the water into the tray so that it doesn't overflow or just trickle.

Once you decide on the size of the outlet hose, there are several ways to connect it to your tray. Essentially, you'll need a nipple that will connect to the tray to connect the hose to. You may be able to find some kind of pre-made fitting in your local hardware store. When I first made my system, I used a part of a brass hose fitting: essentially it was a brass tube with one flared end. I paid $3 for the fitting, which was extravagant. A hole in the tray is drilled large enough for the tube to fit through, but to catch on the flared end.

The hardware store also had cheap plastic T fittings with three 1/2" ends, two of which had a lip above the barbed end, which made them suitable for my purpose. I cut them off above the lip, and got 2 nipples for $0.99. One is pictured here. After the nipple is found or made, I used a good, strong epoxy to glue it on to the tray so that the flared end sits below the level of the tray in the hollow that I pounded in. If you want, you can silicone that too.

With the tray finished and the nipple glued in, the hard part is done. Simply prop up the ends on your bench, with the drain-hole end a bit lower than the other. I bought a small fountain pump (80-120 Gallons per hour) for $10 at my local nursery, but they are also available online. I've seen them at HarborFreight.com, but you'll want to check around for a good price. A 65 GPH pump will work if you have a reservoir that is only a foot or so below your tray, but it probably won't lift the water much higher than that.

Underneath your bench, fill a reservoir with rain water or some other clean water, and put your pump in it. For reservoirs, I've been pretty happy with clear Rubbermain storage containers, but a bucket would work just as well. Then, you'll simply run a hose from your pump into the top end of your tray, and a hose from your nipple back down to the reservoir. I prefer to have a longer hose attached to the pump and a short drain hose, with the reservoir near the drain end of the tray or trays.

It is adviseable to change your reservoir water frequently. Although moving water is less likely to promote infections than standing, water that had accumulated nutrients and organic mater may still be dangerous. A fungicide/anti-biotic/anti-viral such as Physan 20 may be worth experimenting with in the water, though I have had no problems with water changed every week or two.

That about covers it. The pump is then hooked up to a timer (unless you want to run it all the time). I genearlly water for an hour first thing in the morning, and then again around noon, but I don't have a good justification for it. In any case, a digital timer will cost $15-20 , but cheaper analog ones can be had for $5-8. They're especially cheap after Christmas when timers intended for outdoor lights are marked down.

I might as well end with a brief list of supplies and costs:

Tools : a saw that can cut metal, a drill with bits, pliers, ball-peen hammer, a tape measure or ruler.


Metal stud material (?) = $5

Epoxy = $3

Silicone Caulk = $4

Small fountain pump = $10

Suitable sized hose = $5

Nipple for outlet = $1-3

Duct Tape = $4

All in all, not much work or much money, and your Phrags will love you. Just make sure that your Phrags are suitable for quasi-hydroponic culture first!

Here you can see one of the cheap, plastic hose attachments that is epoxied into a tray. You may notice that I skipped a step on this one and didn't beat in an indentation with a hammer. This one was experimental; I also folded the end flaps in reverse order.
Cautionary Note : This is an experimental system. Try it at your own risk; I will take no responsibility for your dead plants!

I've found this system suitable for many Phrags and Disas. Some dry-growing Phrags will not do well in such a wet environment. DO NOT grow Paphs this way! The roots will certainly rot and the plants will die.

Furthermore, pot your Phrags in a hydroponic medium. Bark or other organic mediums will decompose and inhibit air flow to the roots. I've had good results with a bark medium on top of a pot half full with hydroton, as long as good air movement is available.

These two photos show some new Phrags growing in the quasi-hydro system. The trays in these photos are 2 1/2 inches deep rather than 1 1/2, as described above. To the right, you can see the simple reservoir system with the submersible pump (the water is getting a bit low!). This tiny reservoir only holds about 3 gallons.

The other end of the hose that is attached to the pump flows directly into the upper ends of 4 trays. The trays empty directly into the reservoir.