Looking for specific info on fertilizing

[DevFox]

How does one go about figuring out how much fertilizer to add to a plant where the pot has no drainage hole, so the water/fertilizer solution is not ran through the pot, and no occasional leeching/flushing out of the media is done? What gets added to the container stays there until the plants takes it up, or the medium breaks down to the point that it needs to be replaced.

Currently, I'm looking to figure this out for my phalaenopsis.

I'm sure there's a better way to ask this question, but I can't remember or don't know the specific terms regarding watering and potting methods, so please excuse me. Thanks.

[Dusty Ol' Man]

IF the pot has no drainage, and IF the water stays in the pot, THEN you will end up with suffocated roots which will rot. These plants need humid air around the roots. Not wet feet. If I have misunderstood your description, my apologies. But this is what I got from your post. Once you address this issue, then fertilizer can be addressed.

[Paphluvr]

Is it a plastic pot? Your best bet would be to drill some drainage holes and than your question is moot and the plant will be much happier.

[Dimples]

The fertilizer-to-potting-mix ratio you’re looking for doesn’t exist for the extended use you desire. Especially if you’re waiting until the medium has broken down.

[DevFox]

Oh, you guys are concerned by the description of the potting. Sure, I can see why, but I assure you, its a pretty good setup, at least for phals. The containers are glass, very loosely packed with Besgrow sphagnum moss that was initially moistened just enough that it stilled remained light, fluffy, about 5 cups in volume, with roots extending out to the glass so that I can see the color of the roots, as an indicator of when to add more water, which, during the very dry winters here, is about half a cup of water every 2 months, at which point the roots start to turn that chalky pale that they do when dry. Use to be every 5 days, but then I added an inch layer of horticultural charcoal flakes to the top to act as a mulch, which made all the difference.

This extended period between watering is the reason I've converted to this setup. Worked out better than I thought it would. For example, for one of the orchids, when arranging the root inside, it broke it two places. This phal had the most fragile roots I've ever come across. Anyway, when a break occurs, unless I let the break dry out first before potting, it inevitably starts to rot for about a centimeter from the break, turning mushy and black. But in this setup, through the glass, I can see the root remained all green and firm, even though the wound is still open, no callus, no blackening or yellowing.

I do add springtails to all the orchids, and dialed in on the perfect amount of water to add, so maybe that's why. Haven't had a single issue with this setup. Which is also surprising because some of these phals had definitely been accustomed to long periods of complete dryness, so you would think some of these roots would have taken issue with now being in a consistently moist environment.

Anyway, now that this setup has proven to be successful, what I need to figure out now is how to fertilize these phals in this setup.

---------- Post added at 10:02 PM ---------- Previous post was at 09:48 PM ----------

Originally Posted by Dimples

The fertilizer-to-potting-mix ratio you’re looking for doesn’t exist for the extended use you desire. Especially if you’re waiting until the medium has broken down.

There's no analysis of the typical percentage of nitrogen, potassium, etc., of the dry weight of phal orchids, along with the typical growth rate per year?

[estación seca]

Nutrients in fertilizers are in the form of salts, so they will dissolve in water. The additional anions or cations associated with the nutrients are mostly not used by the plants. In your setup they would accumulate and increase the salinity of the medium, quickly approaching toxic levels.

I don't see a solution, other than periodically flooding the container with pure water to carry off the salts, then pouring it out. During warm weather it might evaporate fast enough to continue providing enough air at the roots. I wouldn't soak Phals in moss during cool temperatures.

[Dimples]

There’s no way to actually do that in reality. On paper, sure.

[Ray]

FWIW, for plants grown in semi-hydroponics that get fed at every watering, I have always used and recommended 25 ppm N (Divide 2 by the %N in the fertilizer to get the required teaspoons/gallon). I imagine that would work with moistend moss, as well.

HOWEVER...In semi-hydroponics, the medium is flushed routinely (at every watering, in my setup). What you're doing/proposing will certainly lead to root death over time unless you take extra precautions.

A 25 ppm N solution of most fertilizers will contain a total of 150-200 mg of dissolved salts per liter. The plant will only take up the solution in direct contact with its roots and what little bit gets wicked to them, and that is but a tiny fraction of what you apply. The rest of it precipitates in the medium as the water evaporates. As you repeatedly fertigatem that preceipitate builds up more and more and will eventually reach a level that is damaging.

For example, if your plant has 3 feet of total root length, and the roots are 1/4" (6mm) diameter with 0.5 mm velamen thickness, when you apply that 200 ppm TDS solution uniformly to the moss, the plant will only absorb something on the order of 0.15 mg of the 200 mg applied, leaving 92% of the solids to accumulate.

I suspect that if you grow in a very humid environment, so evaporation is slow, and you completely replace the moss every few months, you might be able to get away with it, but otherwise, you're asking for trouble down the line.