old rusty nails

Clarification of my post about hydrangea flower color and rusting nails:
I may have gotten confused about which direction the color of hydrangea blossoms relating to pH shifts, and which direction the pH shifts in relation to rusty nails.  

It’s not quite as direct a relationship as I thought.  

First, it’s just Hydrangea macrofolia I was talking about.  Then, genetics is a factor, an individual plant may be going to bloom white, and another individual plant may have variability of flower color.  If it does, then soil pH is a factor, and bioavailability of aluminum in the soil is a factor, and iron oxide can effect the soil chemistry.

As in all biological, ecological and biochemical inter-reactions, it’s complex.  If someone does extensive experimentation and observation, I would love to know.  

I will probably remain uncertain how it works, and continue to throw the rusty nails under the hydrangeas 😊.