Hydrangea Quercifolia
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''Hydrangea quercifolia'', commonly known as oakleaf hydrangea or oak-leaved hydrangea, is a
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of
flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...
in the family
Hydrangeaceae Hydrangeaceae is a family of flowering plants in the order Cornales, with a wide distribution in Asia and North America, and locally in southeastern Europe. Description The genera are characterised by leaves in opposite pairs (rarely whorled or ...
. It is
native Native may refer to: People * '' Jus sanguinis'', nationality by blood * '' Jus soli'', nationality by location of birth * Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory ** Nat ...
to the southeastern United States, in woodland habitats from
North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...
west to
Tennessee Tennessee (, ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Kentucky to the north, Virginia to the northeast, North Carolina t ...
, and south to
Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
and
Louisiana Louisiana ( ; ; ) is a state in the Deep South and South Central regions of the United States. It borders Texas to the west, Arkansas to the north, and Mississippi to the east. Of the 50 U.S. states, it ranks 31st in area and 25 ...
. A
deciduous In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...
shrub with white showy flower heads, it is grown as a garden plant, with numerous
cultivar A cultivar is a kind of Horticulture, cultivated plant that people have selected for desired phenotypic trait, traits and which retains those traits when Plant propagation, propagated. Methods used to propagate cultivars include division, root a ...
s available commercially. Its
specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...
combines the
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
words ''quercus'' ("oak"), and ''folium'' ("leaf"). However, it is not closely related to oak species (''Quercus'').


Description

''Hydrangea quercifolia'' is a coarse-textured
deciduous In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...
shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...
growing to tall with an open crown. The plant sprouts shoots from underground
stolons In biology, a stolon ( from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as a runner, is a horizontal connection between parts of an organism. It may be part of the organism, or of its skeleton. Typically, animal stolons ar ...
and often grows in colonies. Young stems are covered in a felt-like light brown bark, and the larger stems have attractive cinnamon-tan-orange
bark Bark may refer to: Common meanings * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Arts and entertainment * ''Bark'' (Jefferson Airplane album), ...
that shreds and peels in thin flakes. The
leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...
are yellowish green to dark green on top and silvery-white underneath. They have three, five or seven pointed lobes and are 4–12 in (10.2–30.5 cm) long and almost as wide. They vaguely resemble larger versions of oak leaves, similar to ''
Quercus An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...
'' species with lobed foliage. Plants in shade have larger leaves than those grown in sun. The leaves turn rich shades of red, bronze and purple in autumn that persist in winter accompanying the persistent dried flower-heads.


Flowers

''Hydrangea quercifolia'' flowers are borne in erect
panicles In botany, a panicle is a much-branched inflorescence. (softcover ). Some authors distinguish it from a compound spike inflorescence, by requiring that the flowers (and fruit) be pedicellate (having a single stem per flower). The branches of a p ...
6–12 in (15.2–30.5 cm) tall and 3–5 in (7.6–12.7 cm) wide at branch tips. Flowers age in colour from creamy white, aging to pink and by autumn and winter are a dry, papery rusty-brown. Unlike bigleaf hydrangea (''Hydrangea macrophylla''), flower color does not vary with
soil pH Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the neg ...
. Flower color does, however, vary throughout each growing season. The flowers are a pale green as they emerge and open to a bright white, ageing to either pink or brown (depending on the cultivar/seedling). ''Hydrangea quercifolia'' and '' Hydrangea paniculata'' are the only hydrangeas with cone-shaped flower clusters (i.e.
panicles In botany, a panicle is a much-branched inflorescence. (softcover ). Some authors distinguish it from a compound spike inflorescence, by requiring that the flowers (and fruit) be pedicellate (having a single stem per flower). The branches of a p ...
); all the others have their flowers in ball-shaped or flat-topped clusters, called umbels. Like many other ''
Hydrangea ''Hydrangea'' ( or ) is a genus of more than 70 species of Flowering plant, flowering plants native plant, native to Asia and the Americas. Hydrangea is also used as the common name for the genus; some (particularly ''Hydrangea macrophylla, H. m ...
'' species, oakleaf hydrangea
inflorescences In botany, an inflorescence is a group or cluster of flowers arranged on a plant's stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a main axis ( pe ...
are composed of two flower types; showy flowers with enlarged petal-like
sepals A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 Etymology The term ''sepalum'' ...
and inconspicuous flowers with non-showy petals and sepals. The showy flowers, whose function is to attract pollinators, typically obscure the inconspicuous flowers to some degree. Although faint, ''Hydrangea quercifolia'' flowers have a pleasing scent. The
floral scent Floral scent, or flower scent, is composed of all the volatile organic compounds (VOCs), or aroma compounds, emitted by floral tissue (e.g. flower petals). Other names for floral scent include, aroma, fragrance, floral odour or perfume. Flower sce ...
in oakleaf hydrangea is stronger than that of the other commonly cultivated ''Hydrangea'' species. Presumably the function of the floral scent is to attract pollinators, although this has not yet been studied. The fragrance can be described as being most similar to ''Syringa reticulata'' (Japanese tree lilac), although not as strong.


Fruit

The fruit of ''Hydrangea quercifolia'' are dry dehiscent capsules which are green following
pollination Pollination is the transfer of pollen from an anther of a plant to the stigma (botany), stigma of a plant, later enabling fertilisation and the production of seeds. Pollinating agents can be animals such as insects, for example bees, beetles or bu ...
and ripen to brown as they mature. The stigmas remain on the fruit and dry to form horn-shaped appendages atop the capsule with an opening between them to allow the seeds to disperse.


Seeds

''Hydrangea quercifolia''
seeds In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be sown, which may include seed and husk or tuber. Seeds are the ...
are quite small, approximately 0.6 mm long (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, allowing them to store for relatively long periods of time at cold temperatures. The seeds typically
germinate Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an flowering plant, angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the sp ...
readily in 7-14 days as long as they are not allowed to dry out after sowing.


Distribution

''Hydrangea quercifolia'' is native to the south eastern United States (Alabama, Florida, Georgia (w.), Louisiana (e.), Mississippi, North Carolina, South Carolina, Tennessee), but naturalized in other parts of the US and widely cultivated elsewhere. In nature, ''Hydrangea quercifolia'' is found in a variety of
habitats In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...
but almost always on well drained, shady slopes. These include riverbanks, bluffs and rocky outcroppings. The tendency of the species to grow on calcareous soils or cliffs as well as deep
alluvial soil Alluvium (, ) is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is ...
suggests it has a wide tolerance of soil substrates as long as they are well drained.


Uses


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 Ornamental plants or ''garden plants'' are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars th ...
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
cultivar A cultivar is a kind of Horticulture, cultivated plant that people have selected for desired phenotypic trait, traits and which retains those traits when Plant propagation, propagated. Methods used to propagate cultivars include division, root a ...
s =‘Brido’ and =‘Flemygea’ have gained the
Royal Horticultural Society The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening charity. The RHS promotes horticulture through its five gardens at Wisley (Surrey), Hyde Hall (Essex), Harlow Carr ...
's
Award of Garden Merit The Award of Garden Merit (AGM) is a long-established award for plants by the British Royal Horticultural Society (RHS). It is based on assessment of the plants' performance under UK growing conditions. It includes the full range of cultivated p ...
. 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 t
USDA Zone 5-9
although the true cold hardiness varies for each cultivar and throughout the species range. 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. Cold hardiness also varies throughout winter, with early loss of cold hardiness being the main limiting factor to cultivation in northern environments. The cultivar 'Ruby Slippers' maintains its cold hardiness well into April, while 'Sikes Dwarf' (despite being very cold hardy in midwinter) loses its cold hardiness very rapidly in late winter. Out of nine cultivars tested, =‘Flemygea’ was consistently the least cold hardy throughout winter.


Diseases

There are several notable diseases that infect ''Hydrangea quercifolia''. Root rot diseases can be fatal while foliar diseases tend to be only cosmetic. Root rot diseases include ''
Phytophthora ''Phytophthora'' (from Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species cause economic losses on crops worldwide, as well as environmental dam ...
'', ''
Pythium ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but '' Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are fre ...
'' and ''
Fusarium ''Fusarium'' (; ) is a large genus of filamentous fungi, part of a group often referred to as hyphomycetes, widely distributed in soil and associated with plants. Most species are harmless saprobes, and are relatively abundant members of the s ...
'', which are all
fungal diseases Pathogenic fungi are fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These orga ...
. 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. The primary foliar disease in oakleaf hydrangea is ''
Xanthomonas ''Xanthomonas'' (from greek: ''xanthos'' – "yellow"; ''monas'' – "entity") is a genus of bacteria, many of which cause plant pathology, plant diseases. There are at least 27 plant associated ''Xanthomonas spp.'', that all together infect at l ...
'' leaf spot, which is a bacterial disease. Management techniques to decrease leaf spot severity include avoiding overhead irrigation and planting resistant cultivars. In a recent study, the cultivars 'Alice' and =‘Flemygea’ had the lowest disease severity while 'Queen of Hearts' had the highest severity. Some wild plants that are native to Florida have even lower disease severity than any cultivar and could serve as an important seed source for breeding disease resistance.


Genomics

Oakleaf hydrangea is a
diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...
species with 2n=2x=36
chromosomes A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most importa ...
. ''Hydrangea quercifolia'' has one of the smallest genomes in the genus (1.95 - 2.17 pg 2C DNA). In nature, the
genetic diversity Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species. It ranges widely, from the number of species to differences within species, and can be correlated to the span of survival for a species. It is d ...
of ''Hydrangea quercifolia'' is
structured Structuring, also known as smurfing in banking jargon, is the practice of executing financial transactions such as making bank deposits in a specific pattern, calculated to avoid triggering financial institutions to file reports required by law ...
geographically in six 'clusters' of genetically similar
populations Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...
. These genetic clusters are weakly differentiated but each one has unique genetics nonetheless. In addition to neutral genetic diversity (13.5% of the diversity), there is evidence of genomic
selection Selection may refer to: Science * Selection (biology), also called natural selection, selection in evolution ** Sex selection, in genetics ** Mate selection, in mating ** Sexual selection in humans, in human sexuality ** Human mating strat ...
in response to climatic variables (11.3% of genetic diversity) of which,
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...
seems to play a major role.


Conservation

The native range of ''Hydrangea quercifolia'' appears to be contracting, despite high abundance in the central portion of the range. In a recent survey of the species, 23% of previously recorded
populations Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...
no longer existed and many of the remaining populations were at high risk of
extirpation Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with extinction, global extinctions. Local extinctions ...
. Causes of local extirpation was attributed to
habitat loss Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...
or degradation often times due to
invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...
, logging or commercial development. Oakleaf hydrangea was noted as not tolerating high
competition Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indi ...
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 Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species. It ranges widely, from the number of species to differences within species, and can be correlated to the span of survival for a species. It is d ...
.


Symbolism

''Hydrangea quercifolia'' was declared the official state wildflower of
Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...
in 1999.State Botanical SymbolsBy Alan McPherson, p.3


Gallery

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


References


External links


Georgia Wildlife Federation: ''Hydrangea quercifolia''
— (non-scholarly but informative)

— Information on growing Oakleaf hydrangeas
Heronswood Nursery: "Hydrangea Care and Culture"
{{Taxonbar, from=Q368161 quercifolia Flora of the Southeastern United States Garden plants of North America Shrubs Symbols of Alabama