Hydrangea serrata is a species of flowering plant in the family Hydrangeacea, native to mountainous regions of Korea and Japan. Common names include mountain hydrangea and tea of heaven. Growing to 1.2 m (4 ft) tall and broad, it is a deciduous shrub with oval leaves and panicles of blue and pink flowers in summer and autumn (fall). It is widely cultivated as an attractive ornamental shrub throughout the world in areas with suitable climate and soil.
Considerable difficulties exist in the nomenclature for H. serrata and closely associated hydrangeas. It is treated here as an individual species in accordance with van Gelderen and van Gelderen. Many botanists, however, view it as no more than a subspecies of H. macrophylla.
H. serrata is similar to H. macrophylla except it is a smaller more compact shrub with smaller flowers and leaves; it is also more hardy. With a rounded habit, it features dark green, serrated (toothed), ovate leaves to 15 cm (6 in) long, and clusters of long-blooming blue or pink lacy flowerheads in mid- to late summer. Both showy sterile florets and less showy fertile florets appear in each cluster. The flowers are perfect, having both male and female parts; they are insect-pollinated.
H. serrata is best grown in rich, medium moisture, well-drained soils in partial shade. It tolerates full sun only if grown with consistently moist soils. Soil pH affects the flower color in the same manner as it does with H. macrophylla — namely, bluish in highly acidic soils and lilac to pink in slightly acidic to alkaline soils. Limited colour change can be achieved with pink and blue varieties on neutral soils by the careful use of soil additives. The flowers occur on old wood, and little pruning is needed. It may be pruned after flowering by cutting back flowering stems to a pair of healthy buds. Weak or winter-damaged stems can be pruned in early spring.
It is winter hardy to USDA Zone 6, and it can be grown in USDA Zone 5 with protection (e.g., mulch and burlap wrap). It may lose significant numbers of flower buds or die to the ground in harsh winters, impairing or decimating the bloom for the coming year. Plants are hardy to about −13 °F (−25 °C) when dormant, but the young growth in spring can be killed by late frosts.
H. serrata makes a good specimen or accent plant for protected locations near homes or patios. It can be grown as a low hedge, and it is quite wind tolerant.
Seeds can be surface sown in a greenhouse in spring. When large enough, seedlings may be outplanted into individual pots. Softwood cuttings can be rooted during summer, as can hardwood cuttings during fall and winter. Mound layering can be accomplished in the spring.
The leaves of mountain hydrangea contain phyllodulcin, a natural sweetener, and are used to make regionally popular herbal teas (sugukcha in Korea and amacha in Japan). Amacha tea is used in Japan in the celebration Buddha's birth.
- RHS A-Z encyclopedia of garden plants. United Kingdom: Dorling Kindersley. 2008. p. 1136. ISBN 1405332964.
- C.J. van Gelderen; D.M. van Gelderen. 2004. Encyclopedia of Hydrangeas. Timber Press. 280 p.
- Sandra Reed; Timothy Rinehart. Hydrangea Macrophylla and Serrata - Should We Lump 'em Or Split 'em?
- "Changing the color of hydrangeas". Hydrangeas! hydrangeas!. Retrieved 23 June 2013.
- "RHS Plant Selector - Hydrangea serrata 'Bluebird'". Retrieved 23 June 2013.
- "RHS Plant Selector - Hydrangea serrata 'Diadem'". Retrieved 23 June 2013.
- "RHS Plant Selector - Hydrangea serrata 'Miranda'". Retrieved 23 June 2013.
- "RHS Plant Selector - Hydrangea serrata 'Preziosa'". Retrieved 23 June 2013.
- "RHS Plant Selector - Hydrangea serrata 'Rosalba'". Retrieved 23 June 2013.
- "RHS Plant Selector - Hydrangea serrata 'Tiara'". Retrieved 23 June 2013.
- Accumulation of phyllodulcin in sweet-leaf plants of Hydrangea serrata and its neutrality in the defence against a specialist leafmining herbivore. Mami Ujihara, Masateru Shinozaki and Makoto Kato, Researches on population ecology, Volume 37, Number 2, pp. 249-257, doi:10.1007/BF02515827
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