Calcium and magnesium supplements?

[isurus79]

I add liquid Cal/Mag supplement every time I water my plants and I follow the instructions on the label.

Easy peezy. No need to get more complicated than that!

[Papillon24601]

Oh! Secondary question! Does this count as fertilizer for the orchids we are winter-resting?

[estación seca]

Originally Posted by Papillon24601

Oh! Secondary question! Does this count as fertilizer for the orchids we are winter-resting?

When people speak of withholding fertilizer during the winter, they are speaking mainly of nitrogen. But, plants that aren't growing don't use many minerals, either, so it isn't necessary to give calcium nor magnesium during winter unless deficiency is suspected.

[Ray]

OK. You got me (and my apparently failing memory).

[Orchid Whisperer]

Originally Posted by Ray

OK. You got me (and my apparently failing memory).

I've lost my memory too. One of these days I'll remember where I put it.

[Ray]

If you know you have a pure water source, you need to add stuff, but you're right about the demand being very low.

If you think about the true scale of things, it helps: a plant is about 95% water, and about 4% carbon, which it gets primarily from the air. The remaining 1% is ALL of the rest of the minerals.

For a plant to gain one pound of mass therefore, it must take up and process a mere 4.5 grams of nutrients. Then if you consider that a complete, powdered fertilizer might be what? 25% nutrient ions, an weight maybe 5 grams per teaspoon, that means that takes somewhere in the range of 3- to 4 teaspoons of fertilizer over the time it gains that pound.

So how long does that take? That depends on the plant. A little masedvallia might not gain a full pound in a lifetime. A standard cymbidium may take a couple or three growths to do that, so what? 12-18 months?