Fertilizer question

[eager2learn]

Does the fertilizer that I add get wicked up the clay pellets with the water or does only water get wicked up leaving the fertilizer behind in the pool of water

[DMT]

What I have read is the clay pellets will absorb the fertilizer. The fertilizer is dissolved in the water so this makes sense.

[eager2learn]

Thank you.

A last question:

What are the plant's signs of over fertilization?

[Ray]

Originally Posted by eager2learn

What are the plant's signs of over fertilization?

Leaf tips becoming brown and dried and dying root tips are the most common symptoms, but there really is no excuse for overfeeding.

Orchids are, for the most part, VERY undemanding of fertilizer. For a plant (any plant) to gain one pound of mass - maybe 30 days for corn, a couple years for a cattleya, or a lifetime for a tiny pleurothallid - it must absorb and chemically process about 25 gallons of water but only about 5 grams of fertilizer nutrients.

In nature, orchids see only 10-15 ppm of nutrient ions, but they get that whenever it rains - maybe several time a day. I mimic that by using 25 ppm N (divide 2 by the %N on the label; the result is teaspoons per gallon to use) every time I water, which is probably 2-3 times a week. If I fed once a week, I'd double that.

Adding more fertilizer does not make the plant grow or bloom faster, it actually has negative impacts. As I implied earlier, water is really the driving force for growth. If you can water very often, your plants will grow faster.

[eager2learn]

Hey Ray,

Your website mentioned to feed w/ K-Lite at every watering.

If the clay pellets can absorb/wick water/fertilizer, wouldn't this cause the salt/fertilizer levels to build up?

[Ray]

Originally Posted by eager2learn

Hey Ray,

Your website mentioned to feed w/ K-Lite at every watering.

If the clay pellets can absorb/wick water/fertilizer, wouldn't this cause the salt/fertilizer levels to build up?

Not if they stay wet.

Dissolved solids precipitate and become mineral deposits as the water evaporates. If the pebbles remain constantly moist, all the way to the top, that just won't happen.

In reality, because pebbles DO dry a bit, it is likely to happen, but by using a very dilute fertilizer solution, there just ain't that much to precipitate in the first place, and if you water by flooding the pot and do so relatively frequently, you redissolve quite a bit of it, slowing the deposition process.

If you routinely let the pots dry out, you feed infrequently at higher concentration, or you don't water properly (flushing the pot when you do), it will build up relatively quickly.

Folks who use those three-component hydroponic pots and only top-up the reservoir are setting their plants up for bad poisoning issues...

[chickazilla]

I realize that I'm joining this discussion one year later... but I've noticed a few things in my orchids in semi-hydro this summer so I thought I'd jump in!

I have about 25 orchids in semi-hydro currently, mostly catts, but also miltoniopsis and oncidium types. I noticed for a while that they were developing black leaf tips so I decided to dial back on the MSU fertilizer, using 1/4 tsp. rather than the recommended 3/4 tsp. and that seems to have done the trick. I feed 2x a month in the summer and 1x a month in the winter.

I also started to use distilled water rather than my Brita filtered water, and I water every week, every 7 days.

This adjustment was based not on science but intuition. In semi-hydro, there's a pool of fertilized solution that feeds the roots, or shall I say over-feeds the roots, for far longer than with organic media. So a very weak solution seems to make sense. I may be wrong and I'm open to being corrected.

Either way, no more black leaf tips! It's also resolved my issues with salt build up at the top. Hope this is helpful or useful to someone out there. Happy growing!

[Roberta]

Chickazilla -
2 things together did the trick - less fertilizer, and also distilled water - The Brita filter does not remove solids from the water. Maybe it improves the taste by removing chlorine and perhaps organics that might have odor, but does nothing to improve the water from the point of view of the plants. (I looked it up, most of what it takes out is not there in the first place) Zero Water filters do take out minerals - as do reverse-osmosis systems. Depending on what part of Los Angeles you are in, the tap water is likely to have high mineral content (especially calcium bicarbonate) so lowering that is beneficial. But don't ever use "softened" water - most water softeners replace calcium with sodium, which terrible for plants even if it tastes better!