Hydrangeas are a genus of flowering shrubs known for their showy, often large, clusters of blooms. The name Hydrangea is derived from the Greek words for water, hydor, and jar, angos, referring to the shape of the plant’s seed capsules, which require constant moisture to thrive. While widely cultivated across the globe today, the origins of the approximately 70 species are geographically split between two distinct regions. The majority are native to East Asia, but a smaller, significant group evolved independently in the Americas.
The Dominant Origin: East Asia
East Asia, particularly Japan, China, and Korea, is the primary center of diversity for the Hydrangea genus. The earliest documented cultivation occurred in Japan, where native species were grown in gardens. Japanese culture assigned a symbolic meaning to the flower, known as ajisai, associating it with heartfelt emotion, gratitude, and apology.
The Hydrangea macrophylla, known commonly as the bigleaf hydrangea, is native and endemic to Japan. This species is the source of the most recognizable garden types, including the mophead and lacecap varieties. The natural wild form features the lacecap structure, with a few large, sterile flowers surrounding a center of smaller fertile ones.
Hydrangea paniculata, often called the panicle hydrangea due to its cone-shaped flower clusters, has a wider native range across eastern Asia, including China and Japan. H. paniculata is recognized for being more cold-hardy and sun-tolerant than its bigleaf relative. This made it a valuable species for later global cultivation.
Species Native to North America
A separate group of hydrangeas evolved naturally in the temperate regions of North America. Fossil evidence suggests that hydrangeas have been present here for a very long time, dating back 40 to 65 million years. These North American species differ significantly in their morphology and growing requirements from their Asian counterparts.
The Hydrangea arborescens, known as the smooth hydrangea, is native to the Eastern United States. This species is characterized by large, rounded flower clusters that are naturally white or greenish-white. It is one of the few species that blooms reliably on new wood, meaning it produces flowers on the growth made in the current season.
The Hydrangea quercifolia, or oakleaf hydrangea, is another distinct species native to the Southeastern United States. It is identifiable by its deeply lobed leaves, which closely resemble those of an oak tree. The foliage also offers seasonal interest, turning rich shades of red and bronze in the autumn. These species were the first hydrangeas to reach Europe, arriving in England in 1736.
Global Introduction and Hybridization
The movement of hydrangeas from their native habitats to worldwide gardens began in the 18th century. The first species to arrive in Europe was the North American H. arborescens in 1736. However, the ornamental varieties that would define the genus in the West were the Asian species.
The popular H. macrophylla arrived in Europe later, brought from China to England in 1788. This species quickly gained popularity for its large, colorful flower heads, leading to its rapid adoption in European and North American gardens. Other species, such as H. paniculata, were also introduced during this period.
The modern diversity of hydrangeas is largely a result of intense breeding and hybridization efforts that followed their introduction. Breeders focused on creating new cultivars that offered different colors, flower shapes, and greater cold tolerance and the ability to rebloom. These programs allowed hydrangeas to thrive in non-native climates across the globe.