Hydrangea hirta

A small deciduous shrub reaching 3 to 4 ft in height.[5] This shrub contains intricate hairy branches that are twisted and bent at opposite angles.[5] The leaves on this shrub are deep toothed, and are covered in stinging hairs.[6] Hydrangea hirta has alternating leaves that are 5 to 8 cm long with an egg shape that comes to a pointed tip.[6] Yellowing and dropping of the leaves commences in August.[6]  As this shrub gets older the branches and leaves begin to smooth due to the loss of the stinging hairs.[6]

The flowers of this shrub tend to grow in small clusters that are light blue to white in color.[6] An individual flower of this species measures 5 cm in diameter with 5 petals and 10 stamens; this species lacks the ornamental bracts that many other hydrangea species possess.[6]  Each flower is fertile, and contains an urceolate seeds swell in the middle and begins to narrow at the top within the flower clusters that contain a central stem bearing a single terminal flower that develops first, the other flowers in the cluster developing as terminal buds of lateral stems.[7] At the base of a flower pod the typical forming of the whorl that encloses the petals and forms a protective layer around a flower in bud is fairly small reaching to be approximately 2 to 3 inches across.[7]

This shrub is native to the mountain ranges of Japan, and extends from the Himalayas through China to Taiwan.[1]  In Japan the Hydrangea Hirta species is located in the cool-temperate rainforest belt, otherwise known as the Montane Temperate Rainforest.[6] This rainforest belt had a range of 1200 meters in elevation in Kyushu, at 1,000 – 1800 meters in Shikoku, 800 – 1650 meters in Chubum and the lowlands of south Hokkaido.[1] An example of where this species can be located  is in the Tsuga Sieboldii Forest that covers the Pacific side of Honshu and Shikoku where this shrub is a species that helps compose the 20% to 40% shrub cover layer in the lower area of the orotemperate belt.[1]  

Hydrangea hirta is a slow growing deciduous species that requires podosolic soils that are more acidic, heavily leached, and moist, with colder and wetter climate conditions.[2] This species is shade tolerant and prefers areas of light shade with partial or full shade.[6] The reproduction of this species is completed by bee pollination with a blooming season that starts in June or late spring and ends in the early summer.[6] However, bee pollination is not the only way this species reproduces, other forms of reproduction for this species includes the  ability to reproduce from the parent stock by the breaking of woody stems, of semi hardwood stems, softwood stems, and the ability to grow new plants from buried aerial stems that will eventually break off and make new plants.[6]

Hydrangea is pronounced hy-DRAIN-juh. Hydrangea is Greek in origin, and comes from Greek hudro- meaning “water” and angeion meaning “a vessel” describing to the shape of the cup shaped fruit and the capsule the fruit is contained in.[8] The hirta portion of this species name means “hairy”, and is pronounced HUR-ta.[9] Another name for this species is Hortensia hirta. Hortensia is a Latinised version of the French given name Hortense, referring to the wife of Jean-André Lepaute.[10] The vernacular name for this species is Viburnum hirtum.[11] While viburnum comes from a Latin origin, and means a small shrub or tree within the temperate and warm regions that bare flat or rounded clusters of white flowers.[11] While hirtum is also Latin in origin, and means “hairy” with a thick growth.[9] In Japan the name for this species is ko-ajisai meaning small hydrangea.[6]

Hydrangea hirta f. albiflora[12]

Hydrangea hirta f. lamalis[12]

Hydrangea hirta var. albiflora[12]

This species has started to be used horticulturally and in landscaping. The seeds for this species can purchased online through a multitude of vendors online, and are commonly found in Europe include the United Kingdom, and parts of the United States.[3] In the European countries that this species can be found in it is notably susceptible to honey fungus.The leaves of this species can be eaten once they have been cooked, and is usually served with rice.[13]

This species has also been used in a wide variety of studies and research projects. A recent project that was conducted by the Department of Forestry at Kyoto University in Kyoto Japan conducted its research on spatial arrangement of the floral buds of plants which perform functions such as climbing and protection of the terminal parts showing their stems nature with emphasis on herbivory on the shoots that have grown in the new growing season.[14] Another portion of this study was done on the competition from surrounding species and compare the requirements that is needed for the support of the species to grow.[14] A recent article that was published by the University of Chicago Press was on an already conducted research project that included a variety of Hydrangea species, including the Hydrangea hirta that was on the phylogenetic implications of seed morphology the species.[15] This study was conducted on eleven seed characteristics including shape, primary sculpture, secondary sculpture, and appendages.[15] The last example of a research study was done on the genome size and base composition on a variety 16 species and subspecies of hydrangea, including hydrangea hirta.[16] The study showed that natural hybrids between thy hydrangea species are rare.[16] However, this study stated that  there have been natural hybrids found in the Izu Peninsula of Japan between Hydrangea hirta and Hydrangea scadens.[16] However, for breeding programs and or potentially enlarging the genetic diversity in cultivated species this study looked at the natural hybrids evolutionary development and diversification.[16]

The charity Plants For a Future: earth, plants, people provide a list of closely related species.[2] The species that are closely related to Hydrangea hirta include: Deinanthe bifida (False Hydrangea), Deutzia scabra (Fuzzy Deutzia), Dichroa febrifuga, Hydrangea anomala (Climbing Hydrangea), Hydrangea arborescens (Wild Hydrangea), Hydrangea aspera (Rough-leaved Hydrangea), Hydrangea macrophylla (Bigleaf Hydrangea), Hydrangea paniculata (Panicled Hydrangea), Hydrangea serrata (Mountain Hydrangea), Hydrangea serrata amagiana (Tea of Heaven), Hydrangea serrata thunbergii (Sawtooth Hydrangea), Philadelphus coronarius (Sweet Mock Orange), Philadelphus delavayi (Chinese Mock Orange), Philadelphus lewisii (Indian Arrowwood), Philadelphus pubescens (Hoary Mock Orange), Philadelphus x virginalis (Virginal Mock Orange), Platycrater arguta (Cobweb flower), Schizophragma hydrangeoides (Moonlight Chinese Hydrangea Vine), and Schizophragma integrifolium (Chinese Hydrangea Vine).[2]

• Hydrangea hirta at Plants for a Future.org.