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Hydrangea quercifolia, commonly known as oakleaf hydrangea or oak-leaved hydrangea, is a species of flowering plant in the family Hydrangeaceae. It is native to the southeastern United States, in woodland habitats from North Carolina west to Tennessee, and south to Florida and Eastern Texas. A deciduous shrub with white showy flower heads, it is grown as a garden plant, with numerous cultivars available commercially.

Its specific epithet combines the Latin words ("oak") and ("leaf"). However, it is not closely related to oak species (Quercus).

Description

Hydrangea quercifolia is a coarse-textured deciduous shrub growing to

Like many other Hydrangea species, oakleaf hydrangea inflorescences are composed of two flower types; showy flowers with enlarged petal-like sepals and inconspicuous flowers with non-showy petals and sepals. (and with a thousand seed weight of 0.0356 g) allowing several to develop within each capsule. Seed color varies from light tan to dark brown with longitudinal striations. Seed shape is ellipsoidal to ovate. Seed storage behavior is considered to be orthodox in nature,

Uses

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Garden history

Hydrangea quercifolia was noted by 18th-century botanist William Bartram in his botanizing exploration from the Carolinas to the Florida panhandle in the 1770s. His first documentation of the plant was located along the "brook called Sweet Water" in what is now south-central Georgia. It was slow to enter British and American gardens. In Britain it flowers less profusely and even has a reputation for being tender.

Cultivation

Hydrangea quercifolia is cultivated as an ornamental plant in gardens and parks. Though frequently seen as an isolated subject in gardens, it is at its best in a natural or landscaped woodland habitat against the backdrop of larger shrubs and trees. It prefers partial to almost full shade, with morning sun and afternoon shade as optimal. It will tolerate drought, but may not flower. In the UK the cultivars ='Brido' and ='Flemygea' have gained the Royal Horticultural Society's Award of Garden Merit.

Propagation is via cutting or division; short sections of clustered stems with some root attached will make a small shrub in a nursery row.

Fresh or dry, the blossoms of Hydrangea quercifolia are attractive as cut flowers.

Cold hardiness

Oakleaf hydrangea is typically stated to be hardy to USDA Zone 5-9, Plants from more northern sources are typically more cold hardy in midwinter than plants from southern sources; moreover, plants native to Florida are substantially less cold hardy than those from other southern sources. while foliar diseases tend to be only cosmetic. Root rot diseases include Phytophthora, Pythium and Fusarium, which are all fungal diseases. Management techniques to decreases incidence of root rot include proper watering (allowing the soil to dry between waterings), removal of diseased plant parts, and fungicides if needed. Compared to other Hydrangea species, oakleaf hydrangea is more susceptible to Fusarium root rot; however, disease severity varies among cultivars with 'John Wayne' and ='Brido' being the most tolerant. Hydrangea quercifolia has one of the smallest genomes in the genus (1.95 - 2.17 pg 2C DNA). In nature, the genetic diversity of Hydrangea quercifolia is structured geographically in six 'clusters' of genetically similar populations. Causes of local extirpation was attributed to habitat loss or degradation often times due to invasive species, logging or commercial development. Oakleaf hydrangea was noted as not tolerating high competition and is therefore highly susceptible to the negative impacts of invasive species. The researchers noted that these effects could be mitigated by protecting and managing land with substantial populations, especially on the species' range edge. To add to the conservation concern, many of the populations on the edge of the native range have unique genetics (especially in Louisiana and Florida) making them especially important to protect as a source of valuable genetic diversity.

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Image:P6164299カシワバアジサイ.jpg|White flowering species type

Image:Oakleaf Hydrangea (Hydrangea quercifolia).jpg|Pink flowering selection

Image:Hydrangea_cultivar,_Ruby_Slippers.jpg|'Ruby Slippers' cultivar

Image:Hydrangea_cultivar,_Munchkin.jpg|'Munchkin'

Image:Oakleaf Hydrangea Hydrangea quercifolia Fall Colors 3008px.jpg|Brown flowers and colored leaves in autumn

Image:Hydrangea quercifolia-SpringLeaf.jpg|Spring leaf shoots

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References

  • Georgia Wildlife Federation: Hydrangea quercifolia
  • Hydrangea Thoughts I: Essay on Hydrangeas - Culture, History and Etymology. — (non-scholarly but informative)
  • Hydrangeas.com: Oakleaf Hydrangea Hydrangea quercifolia — Information on growing Oakleaf hydrangeas
  • Heronswood Nursery: "Hydrangea Care and Culture"