Rhododendron rootstock named ‘Rhodunter 37’

- Inkarho GmbH

A new and distinct Rhododendron hybrid plant used as a rootstock that exhibits hardy and vigorous growth.

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Botanical classification: Rhododendron hybrid.

Varietal denomination: ‘Rhodunter 37’.


The present invention comprises a new and distinct cultivar of Rhododendron hybrid used as a rootstock known by the varietal name ‘Rhodunter 37’. The new variety was discovered in Ahrensburg, Germany. The new variety is the result of a planned breeding program between an unpatented Rhododendron fortunei (female parent)×cv. ‘Cunningham's White’ (unpatented male parent). The new variety exhibits matroclinal morphological features. ‘Rhodunter 37’ exhibits more prominent leaf venation than both parents, but is similar in leaf color and shape to both parents. The new variety has been trial and field tested and has been found to retain its distinctive characteristics and remain true to type through successive propagations.


The accompanying photographic drawings illustrate the new variety, with the color being as nearly true as is possible with color illustrations of this type.

FIG. 1 shows a side perspective view of a typical flowering plant of the new variety grown to a flowering plant;

FIG. 2 shows a close-up view of the inflorescences of the new variety;

FIG. 3 illustrates the new variety with some of the flowers not open; and

FIG. 4 illustrates the new variety with nearly all of the flowers open.


The following detailed description sets forth the characteristics of the new cultivar. The data which defines these characteristics were collected by asexual reproductions performed using tissue culture medium for shoot multiplication of Rhododendron species and which were carried out in Ahrensburg, Germany. The color readings were taken in natural daylight. The field-grown plants were five years old when described (unless indicated otherwise). The soil was a sandy loam mixed with peat. Color references are primarily to The R.H.S. Colour Chart of The Royal Horticultural Society of London.


  • Type: Evergreen shrub.
  • Use: Rootstock.
  • Soil: Sandy loam.
  • Light: Full.
  • Fruit bearing: Very low.
  • Crop time: 1.5 years is required to achieve finished product size that is ready for use as a rootstock.
  • Dimensions at crop time (3 years after grafting. Dimensions depend on the vigor of the scion cultivar):
      • Height.—50 cm.
      • Length.—40 cm.
  • Vigor: 120% of standard using ‘Nova Zembla’ (unpatented) as the standard.
  • Habit: Erect.
  • Hardiness: USDA zone 6a.
  • Rooting habit: Compact root bales.
  • Time to initiate roots: 3 months at 22-25° C. for softwood cuttings.
  • Disease and pest resistance: No observations made to date.
  • Trunk (at 4 years):
      • Diameter.—3 cm.
      • Height.—5 cm above soil.
      • Bark color.—Surface: Year 1: 144A. Year 2: 144A to 175A. Year 3: 175A. Year 4: 177B to 197B-197C. Flesh: 157B.
      • Lenticels.—Inconspicous.
  • Branches:
      • Color.—Surface: Year 1: 144A. Year 2: 144A to 175A. Year 3: 175A. Year 4: 177B to 197B-197C. Flesh: 157B.
      • Length (at one year).—20 cm.
      • Base diameter (at one year).—7 mm.
      • Texture.—Hard.
      • Internode length.—1-2 cm.
      • Branching angle at emergence.—45° angle.
      • Habit.—Compact.
      • Pubescence.—Absent.
      • Branch lenticels.—Inconspicous.
  • Leaves:
      • Arrangement.—Alternate.
      • Length.—13 cm maximum.
      • Width.—4 cm maximum.
      • Shape.—Oblanceolate; with the blade occasionally undulated.
      • Apex.—Truncated.
      • Base.—Triangular.
      • Color.—Adaxial: 147A. Abaxial: 147C.
      • Surface.—Adaxial: Glabrous. Abaxial: Glabrous.
      • Margins.—Entire.
      • Division.—Undivided.
      • Petiole.—Length: 2 cm. Width: 2 mm. Color: 144A. Surface: Glabrous.
      • Leaf stipules.—Sessile.
      • Leaf pubescence.—Absent.
      • Venation pattern.—Feather-veined.
      • Vein color.—Adaxial: 144A. Abaxial: 145C.
      • Leaf texture.—Hard.
      • Leaf appearance.—Typical Rhododendron leaf.
  • Fruit: Fruits (capsules) are usually absent due to self-sterility or incompability with other Rhododendrons. When present, the seed color is 164B.
  • Flower:
      • Arrangement.—Single.
      • Shape.—Widely funnel-shaped.
      • Bud.—Shape: Oblong; Ellipsoid. Width: 20 mm. Length: 40 mm. Color: Closed: 186B. Bursting: 75B. Time of bloom: At 2 years old. Lastingness of bloom: 21 days.
      • Diameter.—8 cm.
      • Depth.—20 mm.
      • Bloom quantity.—13-17 per truss.
  • Petals:
      • Shape.—Fused; the corolla has a wide funnel shape.
      • Number.—7.
      • Length.—40-50 mm.
      • Width of corolla.—70-80 mm.
      • Apex.—Round.
      • Margin.—Slightly undulated.
      • Color.—When opened: Upper surface: 69 A to 69 D. Lower surface: 69 A. Before bud burst: Lower surface: 73 B to 73 C.
      • Peduncle.—Length: 4 cm. Width: 3 mm. Surface: Glabrous. Color: Green when flowers are fully open.
  • Sepals: Not present.
  • Petaloids: Not present.
  • Natural flowering season: Beginning of May through the end of May.
  • Fragrance: Inconspicuous.


  • Stamens:
      • Number.—14.
      • Length.—30 mm.
      • Color.—150D.
  • Anthers:
      • Shape.—Normal Rhododendron type.
      • Color.—158B.
      • Length.—25 mm.
      • Width.—1 mm.
      • Amount of pollen.—Medium.
      • Color of pollen.—150D.
      • Stigma color.—145A.
  • Pistil:
      • Length.—5 cm.
      • Number.—1.
  • Style:
      • Color.—159D.
      • Length.—45 mm.
      • Width.—1 mm.
  • Ovaries:
      • Length.—5 mm.
      • Width.—3 mm.
      • Color.—137C.
      • Position.—Superior.


1. A new and distinct variety of Rhododendron hybrid plant, as illustrated and described.

Referenced Cited
Other references
  • GTITM UPOVROM Citation for ‘Rhodunter 37’ as per PL PBR RNA0002; Jun. 8, 1998.
  • GTITM UPOVROM Citation for ‘Rhodunter 37’ as per QZ PBR 970821; Jul. 29, 1997.
Patent History
Patent number: PP15940
Type: Grant
Filed: Oct 11, 2002
Date of Patent: Sep 6, 2005
Patent Publication Number: 20040073981
Assignee: Inkarho GmbH (Bad Zwischenahn)
Inventors: Walter Preil (Ammersbek), Rainer Ebbinghaus (Ahrensburg)
Primary Examiner: Kent Bell
Attorney: Webb Ziesenheim Logsdon Orkin & Hanson, P.C.
Application Number: 10/270,476
Current U.S. Class: Light To Medium Pink (PLT/239)