Tips on accurate fertilizer dilutions

[guccisimo85]

What’s the best way to measure out fertilizer for small batches (eg watering a single orchid). When you are dealing with small volumes it is really hard to accurately measure out dry fertilizer that calls for 1 tsp per gallon. Is it ok to make up a stock solution? Not sure if there is a shelf life on fertilizer once it’s mixed with water?

Many thanks!

[estación seca]

Mix a gallon or a quart. It will last until you finish it. You can use it on other plants, too.

You have only one orchid?

[guccisimo85]

I like to soak my orchids. I only do a couple at a time because I only have so many containers to soak them in. I don’t like putting more than one in the same water. I know, I know ... it doesn’t bother me so much for the vandas but for all my other orchids I don’t risk it! Makes sense though just to mix up a gallon at a time and keep it on hand.

Originally Posted by estación seca

Mix a gallon or a quart. It will last until you finish it. You can use it on other plants, too.

You have only one orchid?

[camille1585]

You could either mix up a concentrate, or mix more at once that you save for later. I usually mix an entire 10L watering can each time, leave it next to the orchid shelves, and use as needed. The bonus is that in the winter especially the plants get watered with room temperature water instead of very cold tap water.

[Ray]

Check out this other thread:
Simple Fertilizer Dispenser

The way I mix it up, I use 2 ounces of concentrate per gallon, so can use a tablespoon/quart.

[farley101]

This is very cool. I must have missed the original discussion or merely overlooked it. It is definitely a PITA to mix up powdered fert each time it's needed. I water at much less ppm N but something like you use Ray would be a lot easier to be consistent each time.

[guccisimo85]

Does anyone have a resource that covers what ppm to give different kinds of orchids?

[estación seca]

Originally Posted by guccisimo85

Does anyone have a resource that covers what ppm to give different kinds of orchids?

It depends on how fast and vigorously they're growing, not on the kind of orchid. Go to Ray's Web site, firstrays.com . Read everything about Feeding and Watering. You'll learn everything you need to know.

[Ray]

Originally Posted by guccisimo85

Does anyone have a resource that covers what ppm to give different kinds of orchids?

With enough searching, you’ll certainly find people telling you what they give their plants, but that doesn’t mean they’re right or that you should do the same.

Part of the problem is that we don’t really have any idea how much of the applied fertilizer is actually absorbed by the plant. A bare-root vanda only gets what’s absorbed by the velamen the instant it is fed. A cattleya in coarse bark may have a bit more time to absorb, but not much compared to a phalaenopsis in sphagnum. If fed identically, in this scenario the phal would bet the most food while the vanda got the least, which in my experience, is the opposite of what it should be.

The closest related “fact” is that for a plant to gain about 500 g in mass, it must consume about 100 kg of water, but only 5 g of NPK fertilizer.

There is just so much unknown in this field, I have boiled it down to a general recommendation of plants getting 100 ppm N per week (+/-), whether that’s a 100 ppm N solution applied weekly, or 25 ppm N applied every other day.

Note that’s nitrogen concentration, not TDS. There is too much wrong with sharing TDS info.