Also known as Hortensia, Hydrangea is a genus of flowering plants, of family Hydrangeaceae. There are about 70 species in the genus, and they are native to South and East Asia, plus North and South American. They can be deciduous or evergreen, although the cultivated temperate species are generally deciduous.
Most Hydrangea species have white flowers, although some (notably H.macrophylla which is also the most common in cultivation) can be blue or pink according to the pH of the soil (colors as per litmus paper). This effect is due to "hyper-accumulating" of the acidity in the petals by the plant.
Hydrangea are generally grown as ornamental plants due to their large flowerheads. Hydrangea are moderately toxic, although the Japanese ama-cha tea is made from Hydrangea leaves.
Use this tag for all questions about Hydrangea plants