Plant
Hydrangea
Hydrangea (genus)
Also known as: Hydrangea macrophylla, hortensia
A genus of around 75 species of flowering shrubs in the family Hydrangeaceae — native primarily to Asia (especially Japan, Korea, and China) with several species in the Americas. The mophead and lacecap hydrangeas (*Hydrangea macrophylla*) are among the most-cultivated ornamental shrubs in temperate gardens globally. The species is famously pH-indicating: in acidic soils with available aluminum, the same plant produces blue flowers; in alkaline soils, pink flowers. This soil-chemistry-driven color change is one of the most-recognized garden-curiosities in horticulture.
Scientific
Hydrangea (family Hydrangeaceae) contains ~75 species. Principal cultivated species:
- Hydrangea macrophylla — the canonical mophead and lacecap hydrangeas; Japanese origin
- Hydrangea paniculata — panicle hydrangea; cold-hardy; iconic cone-shaped white flower clusters
- Hydrangea arborescens — smooth hydrangea; eastern North American native; the source of the popular Annabelle cultivar
- Hydrangea quercifolia — oakleaf hydrangea; southern US native; large oak-leaf-shaped foliage
- Hydrangea petiolaris — climbing hydrangea; vining habit
The species name Hydrangea derives from Greek hydor (water) + angeion (vessel) — the seed capsules resemble small water jugs.
pH-driven color change
Hydrangea macrophylla flower color responds dramatically to soil pH and available aluminum:
- Acidic soil (pH 5.0–5.5), high aluminum availability — flowers blue (the aluminum binds anthocyanin pigments, shifting color)
- Alkaline soil (pH 6.5–7.0), aluminum unavailable — flowers pink (anthocyanin without aluminum)
- Intermediate — purple, or mixed individual flowers within the same cluster
The mechanism is well-characterized chemistry: anthocyanin pigments shift visible-light absorption depending on the metal ions they bind. Gardeners can manipulate flower color by adjusting soil pH (sulfur or aluminum sulfate for blue; lime for pink).
White-flowered hydrangeas don’t have anthocyanin pigments and don’t respond to pH manipulation; their flowers stay white.
Cultural
Hydrangea cultivation in Japan is documented for over 1,200 years — the species appears in the Manyōshū poetry collection (~750 CE). The Japanese name ajisai gives the early-summer hydrangea-viewing tradition (mid-June, especially at the Meigetsu-in and similar temple gardens in Kamakura). The flower is one of the principal rainy-season seasonal flowers in Japanese aesthetic tradition.
European introduction was via Philipp Franz von Siebold’s 1820s Japanese plant collections; the species was named Hortensia by an early French botanist (in honor of Queen Hortense de Beauharnais), giving the French and German common name hortensia.
In the Azores islands (Portugal), hydrangeas have naturalized to such an extent that miles of hydrangea hedges line roadways and fields — the unofficial floral emblem of the islands.
See also
Auto-generated from this entry’s typed relations: frontmatter, grouped by relation type so the editorial signal isn’t flattened.
- Shares approach with: [[yuzu]] · [[yangmei]] · [[wisteria]] · [[tea]] · [[shiso]] · [[shiitake]]
- Member of: [[plants]]
Sources
- Wikipedia — Hydrangea
A plant entry in the 0mn1.one [[directory]].
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