Patent Publication Number: US-PP32197-P2

Title: Hydrangea plant named ‘H218918’

Description:
Botanical designation:  Hydrangea macrophylla.    
     Cultivar denomination: ‘H218918’. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a new and distinct cultivar of  Hydrangea  plant, botanically known as  Hydrangea macrophylla , commercially referred to as a mophead-type  Hydrangea  and hereinafter referred to by the name ‘H218918’. 
     The new  Hydrangea  plant is a product of a planned breeding program conducted by the Inventor in De Kwakel, The Netherlands and Lengerich, Germany. The objective of the breeding program was to create new strong and freely-branching  Hydrangea  plants with strong sturdy stems, uniform flowering habit, large inflorescences with numerous showy sterile flowers, attractive sterile flower color and good postproduction longevity. 
     The new  Hydrangea  plant is a naturally-occurring whole plant mutation of  Hydrangea macrophylla  ‘Agrihydradrie’, disclosed in U.S. Plant Pat. No. 19,726. The new  Hydrangea  plant was discovered and selected by the Inventor as a single flowering plant from within a population of plants of ‘Agrihydradrie’ in a controlled greenhouse environment in Lengerich, Germany in March, 2015. 
     Asexual reproduction of the new  Hydrangea  plant by vegetative tip cuttings in a controlled environment in De Kwakel, The Netherlands since April, 2016 has shown that the unique features of this new  Hydrangea  plant are stable and reproduced true to type in successive generations. 
     SUMMARY OF THE INVENTION 
     Plants of the new  Hydrangea  have not been observed under all possible combinations of environmental conditions and cultural practices. The phenotype may vary somewhat with variations in environmental conditions such as temperature and light intensity without, however, any variance in genotype. 
     The following traits have been repeatedly observed and are determined to be the unique characteristics of ‘H218918’. These characteristics in combination distinguish ‘H218918’ as a new and distinct  Hydrangea  plant:
         1. Upright and uniformly mounded plant habit.   2. Vigorous growth habit and rapid growth rate.   3. Freely branching habit with strong, thick and sturdy stems.   4. Freely and uniformly flowering habit.   5. Large mophead-type inflorescences with numerous incurved red purple-colored sterile flowers.   6. Good postproduction longevity.       

     Plants of the new  Hydrangea  can be compared to plants of the mutation parent, ‘Agrihydradrie’. Plants of the new  Hydrangea  differ primarily from plants of ‘Agrihydradrie’ in sterile flower form as sterile flowers of plants of the new  Hydrangea  have incurved sepals whereas sterile flowers of plants of ‘Agrihydradrie’ have flat sepals. In addition, plants of the new  Hydrangea  have flatter inflorescences than plants of ‘Agrihydradrie’. 
     Plants of the new  Hydrangea  can be compared to plants of the  Hydrangea macrophylla  ‘HBA215911’, disclosed in U.S. Plant Pat. No. 29,220. In side-by-side comparisons, plants of the new  Hydrangea  differ primarily from plants of ‘HBA215911’ in the following characteristics:
         1. Plants of the new  Hydrangea  have larger inflorescences than plants of ‘HBA215911’.   2. Sterile flowers of plants of the new  Hydrangea  have incurved sepals whereas sterile flowers of plants of ‘HBA215911’ have flat sepals.       

    
    
     
       BRIEF DESCRIPTION OF THE PHOTOGRAPHS 
       The accompanying colored photographs illustrate the unique appearance of the new  Hydrangea  plant showing the colors as true as it is reasonably possible to obtain in colored reproductions of this type. Colors in the photographs may differ from the color values cited in the detailed botanical description which accurately describe the colors of the new  Hydrangea  plant. 
       The photograph on the first sheet is a side perspective view of a typical flowering plant of ‘H218918’. 
       The photograph on the second sheet is a close-up view of a typical inflorescence of ‘H218918’. 
       The photograph on the third sheet is a top perspective view of a typical flowering plant of ‘H218918’ that has been “blued” (left) that is, treated with aluminum sulfate, and a top perspective view of a typical flowering plant of ‘H218918’ that has not been “blued” (right) that is, not treated with aluminum sulfate. 
     
    
    
     DETAILED BOTANICAL DESCRIPTION 
     Plants used in the aforementioned photographs and in the following description were grown during the late spring and early summer in 13-cm containers in a glass-covered greenhouse in De Kwakel, The Netherlands and under cultural practices typical of commercial  Hydrangea  production. During the production of the plants, day and night temperatures averaged 17° C. Plants of the new  Hydrangea  were one year old when the photographs and description were taken. Plants of the new  Hydrangea  can be successfully treated with aluminum sulfate to “blue” the inflorescences. In the following description, color references are made to The Royal Horticultural Society Colour Chart, 2015 Edition, except where general terms of ordinary dictionary significance are used.
     Botanical description:  Hydrangea macrophylla  ‘H218918’.   Parentage: Naturally-occurring whole plant mutation of  Hydrangea macrophylla  ‘Agrihydradrie’, disclosed in U.S. Plant Pat. No. 19,726.   Propagation:
             Type cutting .—By vegetative tip cuttings.     Time to initiate roots, summer .—About two weeks at temperatures about 23° C.     Time to initiate roots, winter .—About 18 days at temperatures about 20° C.     Time to produce a rooted young plant, summer .—About four weeks at temperatures about 23° C.     Time to produce a rooted young plant, winter .—About five weeks at temperatures about 20° C.     Root description .—Thick; typically whitish brown in color, actual color of the roots is dependent on substrate composition, water quality, fertilizer type and formulation, substrate temperature and physiological age of roots.     Rooting habit .—Freely branching; dense.       
       Plant description:
             Plant and growth habit .—Upright and uniformly mounded plant habit; strong and sturdy stems; rapid growth rate and vigorous growth habit.     Plant height .—About 20 cm to 30 cm.     Plant diameter or area of spread .—About 55 cm to 60 cm.       
       Lateral branch description:
             Branching habit .—Freely branching habit; when pinched, about eight to eleven lateral branches develop per plant.     Length .—About 20 cm.     Diameter .—About 6 mm.     Internode length .—About 2.5 cm to 4 cm.     Texture .—Smooth, glabrous; fully developed, woody.     Aspect .—Upright to about 20° from vertical.     Strength .—Strong, sturdy.     Color .—When developing: Close to 144B; at internodes, close to 187A; lenticels, close to 187A. Developed: Close to 144B; at the internodes, close to 187A; when woody, close to 177D; lenticels, close to 187A.       
       Leaf description:
             Arrangement .—Opposite, simple.     Length .—About 7 cm to 10 cm.     Width .—About 6 cm to 8 cm.     Shape .—Ovate.     Apex .—Acuminate to cuspidate.     Base .—Obtuse.     Margin .—Dentate to serrate.     Texture, upper surface .—Smooth, glabrous.     Texture, lower surface .—Rugose, glabrous.     Venation pattern .—Pinnate.     Color .—Developing and fully expanded leaves, upper surface: Close to NN137B; venation, close to 145B. Developing and fully expanded leaves, lower surface: Close to 138B; venation, close to 145C.     Petioles .—Length: About 2 cm to 2.5 cm. Diameter: About 3 mm. Texture, upper and lower surfaces: Smooth, glabrous. Color, upper surface: Close to 145B. Color, lower surface: Close to 145C.       
       Flower description:
             Flower type and habit .—Showy sterile flowers and small inconspicuous fertile flowers arranged on mophead-type terminal panicles; panicles globular in shape; flowers face upright to outwardly depending on their position in the inflorescence.     Fragrance .—None detected.     Natural flowering season .—Plants begin flowering about three months after planting; flowering begins in the early summer and is continuous throughout the summer in Northern Europe.     Flower longevity .—Fertile flowers last about one month on the plant, fertile flowers not persistent; sterile flowers last about four months on the plant, sterile flowers persistent.     Quantity of flowers .—Freely flowering habit; about 60 fertile flowers per panicle and about 130 sterile flowers per panicle.     Panicle height .—About 6 cm to 7 cm.     Panicle diameter .—About 16 cm to 20 cm.     Fertile flower buds .—Length: About 3 mm. Diameter: About 3 mm. Shape: Flattened globular. Color: Close to N57D and 145C.     Sterile flower buds .—Length: About 3 mm. Diameter: About 3 mm. Shape: Flattened globular. Color: Close to N57D and 145C.     Fertile flower diameter .—About 6 mm.     Fertile flower depth  ( height ).—About 5 mm.     Sterile flower diameter .—About 2 cm to 2.5 cm.     Sterile flower depth  ( height ).—About 3 cm.     Petals, fertile flowers .—Quantity and arrangement: Four in a single whorl. Length: About 3.5 mm. Width: About 2 mm. Shape: Ovate. Apex: Acute. Base: Obtuse. Margin: Entire. Texture, upper and lower surfaces: Smooth, glabrous. Color: When opening, upper and lower surfaces: Close to N57D and 144D. Fully opened, upper and lower surfaces: Close to N57D and 144D; color does not change with development.     Petals, sterile flowers .—Quantity and arrangement: Four in a single whorl. Length: About 3 mm. Width: About 3 mm. Shape: Ovate. Apex: Acute. Base: Obtuse. Margin: Entire. Texture, upper and lower surfaces: Smooth, glabrous. Color: When opening, upper and lower surfaces: Close to 145D. Fully opened, upper and lower surfaces: Close to N57D; color does not change with development.     Sepals, fertile flowers .—Quantity and arrangement: Five in a single whorl. Length: About 2 mm. Width: About 2 mm. Shape: Ovate. Apex: Acute. Base: Obtuse. Margin: Entire. Texture, upper and lower surfaces: Smooth, glabrous. Color: When opening, upper and lower surfaces: Close to 144C. Fully opened, upper and lower surfaces: Close to 144D; color does not change with development.     Sepals, sterile flowers .—Quantity and arrangement: Four in a single whorl. Length: About 1 cm to 1.5 cm. Width: About 1 cm to 1.5 cm. Shape: Ovate, incurved. Apex: Obtuse. Base: Obtuse. Margin: Entire. Texture, upper surface: Smooth, glabrous. Texture, lower surface: Rugose, glabrous. Color: When opening and fully opened, upper surface: Close to N57B and towards the base, close to 157B, and venation close to N57D; with development, color becoming closer to 187A and 146B; when “blued”, close to 186D towards the base, close to 145A to 145C, and edges, close to N79D. When opening and fully opened, lower surface: Close to N57D; with development, color becoming closer to 187B and 146C.     Pedicels, fertile flowers .—Length: About 4 mm. Diameter: About 1 mm. Strength: Moderately strong. Aspect: Mostly upright. Texture: Smooth, glabrous. Color: Close to 145B.     Pedicels, sterile flowers .—Length: About 2.5 cm to 3 cm. Diameter: About 1.5 mm. Strength: Strong. Aspect: Erect to about 45° from vertical. Texture: Smooth, glabrous. Color: Close to N57D.     Reproductive organs, fertile flowers .—Stamens: Quantity per flower: Eight. Filament length: About 1 mm. Filament color: Close to 155D. Anther length: About 1 mm. Anther shape: Conical. Anther color: Close to 145D. Pollen amount: Abundant. Pollen color: Close to 155D. Pistils: Pistil quantity per flower: Three. Pistil length: About 1 mm. Stigma shape: Oval. Stigma color: Close to 186C. Style length: About 1 mm. Style color: Close to 145B. Ovary color: Close to 145B.     Reproductive organs, sterile flowers .—Stamens: Quantity per flower: About five to eight. Filament length: About 2 mm. Filament color: Close to 155D. Anther length: About 1 mm. Anther shape: Conical. Anther color: Close to 145D. Pollen amount: Abundant. Pollen color: Close to 155D. Pistils: Pistil quantity per flower: Three. Pistil length: About 2 mm. Stigma shape: Conical. Stigma color: Close to 155C. Style length: About 1 mm. Style color: Close to 155C. Ovary color: Close to 155C.     Seeds, only produced by fertile flowers .—Quantity per fertile flower: About 20 to 30. Length: About 0.5 mm. Diameter: About 0.1 mm. Color: Close to 200C.       
       Pathogen &amp; pest resistance: Under commercial production conditions, plants of the new  Hydrangea  have not been observed to be resistant to pathogens and pests common to  Hydrangea  plants to date.   Temperature tolerance: Plants of the new  Hydrangea  have been shown to be tolerant to temperatures ranging from about 3° C. to about 38° C.