In this post I argue that anything accomplished by watering twice can be achieved by watering with a more dilute fertilizer solution in the first place.
- Pre-watering with water alone means a higher fertilizer concentration will be required to make the same amount of nutrients available to roots.
- Pre-watering with water will result in a gradient where fewer salt ions are present deep in the media but diffusion will equalize the concentrations in hours if not minutes.
- Sphagnum, which can hold huge amounts of water, can easily be over watered by watering twice.
The reason given for pre-watering with water before fertilizing is usually given as preventing root tip burn. I haven't seen root tip burn be a problem even in vanda fertilized at 1Tbs /gallon. This concentration is 8-12 times the amount I normally apply when fertilizing and the salt concentration increases further as drops hanging from vanda root tips evaporate.
So in conclusion I believe that it makes more sense to use a weaker fertilizer solution to start with than to water orchids twice.
-Keith
Water with plain water first before fertilizing?
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