Toxicological trivia from April 22, 2016: Hydrangea (common names hydrangea or hortensia) is a genus of 70–75 species of flowering plants native to southern and eastern Asia (China, Japan, Korea, the Himalayas, and Indonesia) and the Americas. In most species the flowers are white, but in some species (notably H. macrophylla), can be blue, red, pink, light purple, or dark purple. In these species the color is affected by soil pH. For H. macrophylla and H. serrata cultivars, the flower color can be determined by the relative acidity of the soil: an acidic soil (pH below 7), by the influence of sundry agents in the soil, such as alum or iron, will usually produce flower color:a) Closer to blue; b) Pink;c) White.

Correcta answer: a. Read more in WP or in Spanish page: hortensias