Orchid Fertilizer

Orchids, being slow growers of the plant world, a fairly undemanding of fertilizer.

Nitrogen is the important element in any fertilizer, so that is how most professional growers manage their applications.

For weekly application, I recommend a nitrogen concentration of about 100 ppm N. If you divide 8 by the %N on the fertilizer label, the result is the teaspoons/gallon for that level. It is fine to round it a bit for convenience.

 

What a lot of folks don't seem to grasp is that the TDS reading varies widely with the formula of the fertilizer.

If you know the calculated nitrogen concentration, then measure the TDS of the solution, the TDS becomes a great control factor, but if you arbitrarily choose a certain PPM TDS, then your feeding regimen might be too little or too much, and will change if you change fertilizer.

100 ppm N K-Lite might have a TDS of about 250-275 ppm, while 100 ppm N of MSU WW formula might be closer to 500 ppm TDS.

Marni, what TDS does 1/4 tsp/gal (a shade under 100 ppm) of Jack's add to your water supply?

 

Marni, if you're metering pump has a variable mixing ratio, try halving the concentration of the feed and doubling the amount metered. If that's not possible, putting the injection point farther from the delivery end of the hose can help, too.

 

I had another thought: A mixing chamber.

My first thought was a complete DIY project - a 2' long piece of capped 4" PVC pipe with a male and female hose fittings at either end. As the solution enters that volume, it will get mixed by its own turbulence and the outflow will be much more uniform.

Alternately, and easier to do, is to purchase a large filter housing (20" x 4" with at least 3/4" NPT threads to minimize pressure drop), add the hose fittings, and you're set to go. I'd run it "backwards" from the labeled flow direction so the input blasts down from the center of the cap for better mixing. I've seen Pentek "Big Blue" housings available online for under $40.