plant ‘NCRX8’

A new and distinct cultivar of Rhododendron plant named ‘NCRX8’ having prolific, bright cherry-red single flowers, cold hardy to USDA Zone 6b, consistent Fall reblooming, and a dense, compact habit. The new cultivar is a Rhododendron, suitable for ornamental garden purposes.

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Latin name of the genus and species: The Latin name of the novel plant variety disclosed herein is Rhododendron hybrid.

Variety denomination: ‘NCRX8’.

The inventive hybrid was selected from seedlings derived from a controlled cross between evergreen azaleas H2009-242-026 (female, unpatented experimental hybrid) and H2009-308-006 (male, unpatented experimental hybrid). Prior to the designation of the varietal denomination, ‘NCRX8’ was referred to by its experimental code: H2014-136-152.


The present invention comprises a new and distinct hybrid evergreen azalea cultivar hereinafter referred to by the cultivar name ‘NCRX8’. This hybrid azalea was developed by a controlled breeding program at North Carolina State University, in Mills River, N.C. ‘NCRX8’ was selected for its single, cherry-red flowers, floriferousness, dense and compact growth habit, and consistent Fall reblooming. It was selected from the controlled, hand pollination of emasculated female experimental hybrid H2009-242-026 (unpatented) and male/pollen parent experimental hybrid H2009-308-006 (unpatented). ‘NCRX8’ was selected from this population of seedlings after 5 years in trials at the Mountain Horticultural Crops Research and Extension Center in Mills River, N.C.

Container trials were conducted using pine bark media supplemented with 1.04 kg·m−3 dolomitic lime, 0.74 kg·m−3 granulated micronutrients (Micromax; ICL Specialty Fertilizers, Tel Aviv, Israel) and top-dressed with 5- to 6-month slow-release fertilizer (Osmocote Plus 15-9-12, ICL Specialty Fertilizers). Full-sun field trials were conducted in plastic-covered, bark-amended clay soils with minimum winter temperatures of −2° F. (−19° C.) and maximum summer temperatures 98° F. (37° C.). The first asexual propagation of ‘NCRX8’ occurred in 2015 by rooting stem cuttings at the North Carolina State University Mountain Horticultural Crops Research Station, Mills River, N.C. ‘NCRX8’ roots readily from firm softwood cuttings treated with a basal dip of 3,000-5,000 ppm indole butyric acid (potassium salt) in water. ‘NCRX8’ has been found to retain its distinctive characteristics through successive asexual propagations over 6 years.


The following are the unique combination of characteristics of this new cultivar when grown under standard horticultural practices at North Carolina State University, Mountain Horticultural Crops Research Station, Mills River, N.C.

    • 1. Bright, cherry-red single flowers.
    • 2. Cold hardy to USDA Zone 6b.
    • 3. Dense, compact habit.
    • 4. Consistent Fall reblooming.


Records of the parent variety characteristics are not available. The inventor cannot make a comparison to either the seed or pollen parent.


TABLE 1 Additional Plant Flower Color and Type Habit characters Rhododendron Red, single/semi-double Mid-sized/large Hardy to ‘Conlen’ flowers with 120-150 × Zone 7 U.S. Plant Pat. some petaloids. 120-150 cm No. 11,628 P RHS Red Group 46B. Rhododendron Red single semi-double Mid-sized/large Hardy to ‘Conleb’ flowers with 120 × 140 cm Zone 7 U.S. Plant some petaloids Pat. No. 10,581 RHS Red Group 44A. Rhododendron Red/salmon semi- Mid-sized, large Hardy to ‘Conleo’ double flower with 150-180 × 150- Zone 7 U.S. Plant some petaloids 180 cm Pat. No. 11,640 RHS Red Group 44D Rhododendron Cherry red single flowers, Compact, Hardy to ‘NCRX8’ profuse flower display prostrate Zone 6b RHS Red Group 53B. 75 × 90-120 cm


‘NCRX8’ is illustrated by the accompanying photographs, which show the plant's form, foliage, and inflorescences. The colors shown are as true as can be reasonably obtained by conventional photographic procedures. Colors in the photographs may differ slightly from the color values cited in the detailed botanical description, which accurately describe the new hybrid Rhododendron.

FIG. 1 Image showing flowering plants in 3-gallon containers; image taken from 3-year-old container plants grown in Grand Haven, Mich., in 2020.

FIG. 2 Image showing a close-up of a 3-gallon plant; single bright cherry flowers visible. Image taken from 3-year-old container plants grown in Grand Haven, Mich., in 2020.


The following is a detailed description of the botanical characteristics of the new and distinct hybrid evergreen azalea known by the denomination ‘NCRX8’. The detailed description was taken on a 3-year-old container-grown plant in Mills River, N.C., in 2020. Where pertinent, descriptive data was supplemented by observations/measurements taken on a 5-year-old individual located in field trials in Mills River, N.C., as well as information provided from cooperators in Grand Haven, Mich. All colors cited herein refer to The Royal Horticultural Society Colour Chart (The Royal Horticultural Society (R.H.S.), London, 2015 Edition. Where specific dimensions, sizes, colors, and other characteristics are given, it is to be understood that such characteristics are approximations or averages set forth as accurately as is practicable.

  • Plant:
      • Plant type.—Evergreen azalea.
      • Growth habit/form.—Globose, prostrate.
      • Height at maturity.—˜75 cm.
      • Width at maturity.—˜100-120 cm.
      • Roots.—Fibrous.
      • Growth rate.—Moderate.
  • Shoots and branches:
      • Shoots (softwood shoots, current years growth).—Shape: Rounded. Color: RHS Yellow-Green Group 144 C/B. Texture: Pubescent. Pubescence color: RHS Greyed-Orange Group N165B/C. Shoot diameter: 1.5-2 mm. Shoot length: Variable, ranging from ˜7-15 cm.
      • Shoots (prior-year's woody shoots).—Shape: Rounded. Color: Mix of RHS Greyed-Orange Group 165B and RHS Grey-Brown Group N199B/C. Texture: Gently exfoliating. Stem diameter: Generally 3.5-5 mm. Stem length: Variable, ranging from 5-20 cm. Stem aspect: 0-90°.
      • Branches (woody stems).—Shape: Rounded. Color: Mix of RHS Greyed-Orange Group 165B and RHS Grey-Brown Group N199B/C. Texture: Exfoliating. Branch diameter: Approximately 5-10 mm. Branch length: Variable 5-15 cm. Branching: Freely branched at flowering points. Number of lateral branches: Variable, 30-70.
  • Foliage:
      • Type.—Evergreen.
      • Arrangement.—Alternate.
      • Division.—Simple.
      • Shape.—Elliptic to obelliptic.
      • Apex.—Mucronate.
      • Base.—Cuneate.
      • Margin.—Entire; ciliate.
      • Venation.—Reticulate.
      • Internode length.—Approximately 5-15 mm.
  • Immature leaf:
      • Adaxial (upper) surface.—
      • Color.—Mix of RHS Yellow-Green Group 146A/B and RHS Yellow-Green Group 147A.
      • Surface.—Pubescent.
      • Abaxial (lower) surface.—
      • Color.—RHS Yellow-Green Group 146B.
      • Surface.—Pubescent.
      • Pubescence (same color on both sides).—RHS Yellow-Orange Group 19C/D.
  • Mature leaf:
      • Length.—Approximately 3.5-6 cm.
      • Width.—Approximately 2-3.5 cm.
      • Color.—
      • Adaxial (upper) surface.—RHS Green Group 137NN A/B.
      • Abaxial (lower) surface.—RHS Green Group N138B.
      • Surface.—Both sides are lightly pubescent; RHS Greyed-Orange Group 164B/C.
  • Fall/winter leaf color:
      • Adaxial side.—RHS Greyed-Purple Group N186C to RHS Greyed-Purple Group 187A.
      • Abaxial side.—RHS Yellow-Green Group 149B; veins and midrib RHS Greyed- Red Group 180A.
  • Petiole:
      • Shape.—Lunate.
      • Length.—Approximately 5-8 mm.
      • Diameter.—Approximately 1-2 mm.
      • Color.—
      • Adaxial/adaxial side.—RHS Yellow Green Group 144A.
      • Surface.—Both sides are pubescent; RHS Greyed Orange Group 164B/C.
  • Flower:
      • Type.—Congested terminal raceme (truss).
      • Flowering season.—Mid-Spring (Mid-April-Early May into June) reblooms in Early Fall (Late September to through October).
      • Flowering habit.—Free-flowering.
      • Flower number.—2-5 flowers per truss.
      • Consistency in display.—Blooms reliably in the spring and consistently reblooms in the fall.
      • Lastingness of flowers.—Each flower lasts approximately 3-7 days.
      • Fragrance.—None.
      • Self-cleaning or persistent.—Self-cleaning.
  • Truss bud:
      • Length.—Approximately 10-18 mm.
      • Diameter.—Approximately 5-8 mm.
      • Bud scales.—
      • Number.—Variable: 4-7.
      • Length.—Approximately 8-12 mm.
      • Width.—Approximately 5-10 mm.
      • Color.—RHS Yellow-Green Group 145A/B, some bud scales deepen to RHS Red Group 46A (this is more intense in colder temperatures).
      • Texture.—Adaxial side is glabrous; abaxial side is pubescent at tip (RHS Greyed-Orange Group 164 A/B).
  • Emerging flowers:
      • Shape.—Elliptic, acuminate.
      • Length.—2.5-3 cm.
      • Diameter.—6-12 mm.
      • Color.—RHS Red Group 53B/C.
  • Perianth:
      • Diameter at anthesis.—3.5-5.5 cm.
      • Depth.—1.5-3.5 cm.
      • Organization.—Petals are arranged in a single whorl.
      • Aspect.—Facing upwards and outwards.
      • Shape.—Funnel-shaped.
      • Attachment.—Pedicellate.
  • Petals:
      • Length.—3-4.5 cm.
      • Width.—1.5-2 cm.
      • Number.—5.
      • Shape.—Obovate.
      • Apex.—Obtuse.
      • Base.—Acuminate
      • Margin.—Undulate.
      • Fused or unfused.—Fused at the midpoint.
      • Color.—Color is consistent from opening to anthesis. Adaxial (upper) surface: RHS Red Group 53B. Blotch: RHS Red Group 53A/B. Surface: Smooth, silky. Abaxial (lower) surface: RHS Red Group 53C/D. Dorsal Flare: Mix of RHS Red Group 42B and RHS Red Group 53 C/D. Surface: Smooth, silky.
  • Calyx/receptacle:
      • Shape.—Star-shaped, single-whorl of persistent sepals.
      • Sepals.—Number: 5.
      • Length.—5-10 mm. Width: 2-4 mm.
      • Shape.—Lanceolate.
      • Apex.—Cuneate.
      • Margin.—Ciliate. Color: RHS Yellow-Green Group 145A. Surface: Pubescent (RHS White Group 155C).
  • Pedicels:
      • Shape.—Rounded.
      • Length.—0.8-1.5 mm.
      • Diameter.—Approximately 0.5 mm.
      • Color.—RHS Red Group N45B.
      • Surface.—Both sides are pubescent (RHS White Group 155C).
  • Reproductive organs: Generally, flowers are both complete and perfect, although individual flowers may vary.
  • Gynoecium:
      • Pistil number.—1.
      • Pistil length.—3.5-5 cm.
      • Stigma shape.—Orbicular to elliptic.
      • Stigma length.—Approximately 1 mm.
      • Stigma width.—Approximately 1 mm.
      • Stigma color.—RHS Red Group 46A upon opening; RHS Red Group 53A when receptive.
      • Style length.—3-4.5 cm.
      • Style diameter.—Approximately 1 mm.
      • Style color.—RHS Red Group 46A.
      • Ovary shape.—Dome-shaped.
      • Ovary length.—3-5 mm.
      • Ovary diameter.—2.5-4 mm.
      • Ovary color.—RHS Yellow-Green Group 145A.
      • Surface.—Tomentose, RHS Yellow Group 4D.
  • Androecium:
      • Stamen number.—7-10.
      • Anther shape.—Ovoid with two apical pores.
      • Anther attachment.—Dorsifixed.
      • Anther length.—0.5-1 mm.
      • Anther width.—˜0.5 mm.
      • Anther color.—RHS Greyed-Purple Group 183A.
      • Filament length.—2.5-4 cm.
      • Filament diameter.—Approximately 0.5-1 mm.
      • Filament color.—RHS Red Group 46B upon opening RHS Red Group 53C at anthesis.
      • Amount of pollen.—Normal.
      • Pollen type.—Vicinate.
      • Pollen color.—RHS White Group NN155.
  • Other characteristics:
      • Fruit type.—Capsule.
      • Fruit texture.—Pubescent/tomentose.
      • Fruit length.—Approximately 6-10 mm if successfully pollinated, ˜4 mm if not.
      • Fruit diameter.—Approximately 5-10 mm if successfully pollinated, ˜4 mm if not.
      • Fruit color.—
      • Immature fruit color.—RHS Yellow-Green Group 145A.
      • Mature fruit color.—RHS Brown 200D.
      • Seed quantity.—Variable 0 to hundreds.
      • Seed length.—Approximately 1 mm.
      • Seed diameter.—Approximately 0.5 mm.
      • Seed color.—
  • Propagation: Roots readily (>90%) from firm, terminal, softwood stem cuttings taken in mid-summer. ‘NCRX8’ roots well when the bottom 2 cm of the stems are treated for 5 seconds with 3,000-5,000 ppm of potassium salt of indole-3-butyric acid (KIBA) dissolved in water and placed under intermittent mist for 8-10 weeks until roots form.
  • Disease and insect resistance: No significant disease or insect pests have been observed.
  • Cold hardiness: Has been reliably cold hardy in USDA Zone 6b.


1. A new and distinct cultivar of Rhododendron plant named ‘NCRX8’ as herein illustrated and described.

Patent History
Patent number: PP33922
Type: Grant
Filed: Jun 9, 2021
Date of Patent: Feb 1, 2022
Assignee: North Carolina State University (Raleigh, NC)
Inventors: Thomas Green Ranney (Arden, NC), Darren Touchell (Raleigh, NC), Irene Palmer (Raleigh, NC), Andra Nus (Raleigh, NC), Nathan P. Lynch (Raleigh, NC)
Primary Examiner: Annette H Para
Application Number: 17/343,204
Current U.S. Class: Dark Pink To Red (PLT/240)
International Classification: A01H 6/38 (20180101); A01H 5/00 (20180101);