Tuesday, June 9, 2026

HYDRANGEA FLOWERS: THE LITMUS-PAPER FLOWER

The name Hydrangea is Greek (for water vessel), in reference to the shape of the seeds of this flower. Hydrangea is typically a a shrub 3 to 9 feet in height, but it also occurs as smalls trees, typically less than 100 feet tall. It is a plant native to Asia and the Americas (with Asia having more species diversity).


The colors of its flowers can be blue, purple, purplish gray, red, pink, greenish white, or white. 


The color of their flowers depends on the acidity of the soil. For example, their flowers can change color (even in one season), for example from from blue (= acidic soil) to pink (= alkaline soil), if the soil acidity changes. Thus, these flowers are natural pH indicators of the soil.


  Classification

Kingdom Plantae

Clade (6 of them)

Order Cornales

Family Hydrangeaceae

Genus Hydrangea: a genus with about 98 species.

Type Species H. arborescens Linneaus


There are two main inflorescenses (shapes) of the flower heads: round (resemble “pom-poms”) or round, flat with a subdued center core.


Hydrangea prefers consistent moisture and moderate temperatures. Hot, dry summer conditions are not good for them.


Fossil Record: Imprints in Paleogene strata at Jaw Mountain, Alaska.

Also imprints in Miocene deposits in Oregon and California.

Miocene seeds in Poland.


Figure 1. Blue Hydrangea, blue color indicates growth in acidic soil.



Figure 2. Purple, pink Hydrangea.



Figure 3. White Hydrangea. 

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