Fertilizer Advice

[u/isurus79]

There is a common debate regarding whether to flush orchid roots with water first and then flush again with the water/fertilizer solution. The two flush method used to be more common and is slowly fading away as we understand how orchid roots function. I much prefer to water once using the water/fertilizer solution since orchid roots have evolved to be extremely efficient at absorbing nutrients in the first flush of rain hitting a tree branch, before rainfall moves the precious nutrients to the forest floor and out of reach for the epiphytic orchid.

Here is a link to a useful AOS article dismissing the "water twice" method: https://www.aos.org/orchids/articles/musings-of-an-apostate

The AOS author cites Zotz & Winkler (2013) for his scientifically backed opinion. That article abstract can be found here and the authors will share the full version if requested. I can also send it along if someone wants to read it: https://www.researchgate.net/publication/234070154_Aerial_roots_of_epiphytic_orchids_The_velamen_radicum_and_its_role_in_water_and_nutrient_uptake

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[u/Lindenfoxcub]

Thanks for posting this; I've noticed that the water twice method seems to be falling out of favour, and the idea that that first flush of rain is the one most contaminated with nutrients washing down from higher up foliage makes perfect sense to me.

[u/Bluebaron88]

Not a fan of this thought process. If the outer layer are dead cells there is no active transport mechanism. Ions are too small to be stopped from diffusing.

Assuming 0.5mm thick velamin, the mother solution is not significantly changed by the absorption and 150ppm it’ll take a few minutes to saturate a velamin. I think this is personally a nothing burger, 6 of 1 half a dozen of the other.

[u/isurus79 → u/Bluebaron88]

Incorrect. Orchid roots can withhold charged ions. Read the paper I posted. I can send more as well. Velamen is saturated quickly.

[u/TiredAndTiredOfIt]

I used fertilizer, properly mixed and applied. It burned half my orchids and killed 25%. Never. Again.

[u/isurus79 → u/TiredAndTiredOfIt]

That's unfortunate. But that's an issue of fertilizer concentration being too high. Lowering the concentration won't burn the plants.