Hydrangea serrata, commonly known as mountain hydrangea or tea of heaven, is a deciduous shrub native to the cool, mountainous regions of Korea and Japan, often found in forested areas and along stream banks. It grows to a modest size of 1.2 meters (4 feet) tall and wide, with a rounded habit. The leaves are dark green, serrated, and ovate, up to 15 cm (6 inches) long. During mid- to late summer, it produces panicles of blue or pink lacy flowerheads that are highly ornamental, with both showy sterile florets and less conspicuous fertile florets. The flowers are perfect and insect-pollinated.

Mountain hydrangea is valued for its long blooming period, compact size, and the ability to change flower color based on soil pH—blue in acidic soils and pink to lilac in neutral to alkaline soils. It is commonly used as a specimen or accent plant, in borders, and as a low hedge, especially in protected locations near homes or patios. It is also wind tolerant. Hydrangea serrata requires rich, medium moisture, well-drained soils and thrives in partial shade, though it can tolerate full sun if the soil remains consistently moist. Pruning should occur after flowering, and winter-damaged stems can be cut back in early spring. It is winter hardy to USDA Zone 6 but may require protection in Zone 5. The plant may suffer from bud loss or dieback in harsh winters, which can affect blooming.CC BY-SA 4.0