Vanda Royal Blue?

[Dorra]

RainMix:
N ............. 11,8%
P2O5 ........ 2,7%
K2O .......... 13,7%
CaO .......... 11,8%
MgO .......... 3,5%
SO3 .......... 4,8%

This Vanda has 50% sanderiana, 43,75% coeruela, 3,13% dearei and 3,13% tricolor... wonder which is so sensitive...

[Roberta]

Originally Posted by Dorra

RainMix:
N ............. 11,8%
P2O5 ........ 2,7%
K2O .......... 13,7%
CaO .......... 11,8%
MgO .......... 3,5%
SO3 .......... 4,8%

Yessss... lower Phosphorus relative to the other constituents. The other components probably tend to balance themselves out. If you have a pH meter or pH paper, test the fertilizer solution mixed up at the correct level for plant-watering.

Most tap water has some dissolved minerals, so the bit of fertilizer you add doesn't change the pH a lot (buffering capacity) RO water doesn't, so it's important to get a mix that keeps the pH in the range that orchids want (typically, some place between 5.0 and 6.5) So you want to stick to a formulation that is designed for it. (So-called "bloom" fertilizer really doesn't do much for blooming, you can accomplish the same by reducing nitrogen - just just use less fertilizer - in the winter. In the spring, the plant is growing rapidly and needs more)