Last summer, I moved transplanted my hydrangea, aka "Jib-Jubs," to separate it from my quickly-spreading hibiscus syriacus. As I was in a rush to do so, I made the mistake of planting it in a full-sun area with poor (rather sandy) soil. To alleviate the effects of intense all-day sun, I mulched around the plant with some red mulch. The plant underwent difficulty with both the sun and the soil, requiring high levels of attention. But most peculiar was the fact that the hydrangea took on a reddish color not dissimilar to that of the mulch. Is it possible that coloration from the mulch was taken up by the Jib-Jubs, and then manifest in the leaves and flowers? Or is it likely that it was simply the result of a high-stress lifestyle? I recently transplanted Jib-Jubs to a much more suitable location, and would like to re-mulch. But if it's likely that the mulch is the culprit, I am just going to buy some regular nature-colored mulch this time. What sayest thou?
Hydrangea flower color is affected by a number of factors, but the most important one is soil pH, or degree of acidity/alkalinity. The reddish color is usually associated with more alkaline / less acid soils; so the change is probably an indication of a difference in soil pH between the two sites. The mulch is probably contributing to this difference, which has nothing to do with the color of the mulch.
Nothing to do with answering the question (since Vitog already has), but out of curiosity, why do you call it "Jib-Jubs,"??
Thank you for the reply. It seemed unlikely that it would might be the mulch. But, the way that the entire plant took on the same rust-red coloration as the mulch was too much of an odd coincidence to count out. I prefer to give plants atypical names, since they make me chuckle, and the plants themselves don't seem to care. In this case, I especially like the way Jib-Jubs rolls off the tongue. Also, it rarely fails to make me smile. Hope this helps!