re: Fertilizer for Hydrangeas

One of the ways to change the hydrangeas flowers from pink to blue is to treat the soil with Iron shavings or rusty nails.

I have 3 hydrangeas in pots. The flowers have been pink the last few years. I treated 2 of the plants with iron filings this past summer. Waiting to see if I get some blue flower on these plants. I take in these plants during the winter cold snaps and did not mark which plants I treated. So this spring will be a surprise which ones will have blue flower.