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Horticulture Digest

Date Last Edited:  08/24/2001

Hawaii Cooperative Extension Service

Horticulture Digest #101

Amphidiploid Dendrobium Mini Gem, a hybrid with two sets of chromosomes each of D. bigibbum var. compactum of the section Phalaenanthe (P. genome) and the diminutive D. carronii of the section Eleutheroglossum (E. genome), has been utilized successfully in our breeding program to produce miniature, seed-propagated, potted plant cultivars. D. Cathy Beck (UH1221) released earlier is a cross between D. Mini Gem and D. antennatum of the section Ceratobium (C. genome), and has the PCE genome constitution.

Two additional hybrids of amphidiploid D. Mini Gem have performed well, and therefore are being named and released for commercial cropping as potted plants. These are D. Betty Nakada (UH1208) and D. Remy Hartmann (UH1307).

D. Betty Nakada (UH1208)

The cross between amphidiploid D. Mini Gem and D. phalaenopsis var. compactum was made on December 31, 1986, and germinated on April 6, 1987. Like D. Cathy Beck, D. Betty Nakada is precocious. First flowering was obtaine d 21 months after germination on very short pseudobulbs. The average height of the first pseudobulbs with flowers was slightly under 2 inches. The height of pseudobulb at the termination of the evaluation was 10 inches.

  • The flowers of D. Betty Nakada are small, roundish and measure about 1-3/4 inches across (Table 1).
  • Petals and sepals are purple (RHSCC 78A).
  • Multiple arching sprays produced on several pseudobulbs at a given time result in attractive, compact, miniature flowering potted plants.
  • Furthermore, peak flowering period is from October through February, when several florist holidays occur.
  • The short, erect pseudobulbs and small narrow dark green leaves are also desirable characteristics.

Because this hybrid has one set of the E. genome contributed by D. carronii and two sets of the P. genome contributed by D. bigibbum var. compactum and D. phalaenopsis var. compactum, it cannot tolerate hea vy rains. This hybrid probably requires a protective covering for best culture.

Table 1. Characteristics of Dendrobium 
Betty Nakada (UH1208) and D. Remy Hartmann (UH1307)

Characteristics     D. Betty Nakada     D. Remy Hartmann

Scape length (in.)     7.11.3               5.00.9

Spray length (in.)    12.23.6              11.82.1

No. of flowers/spray  10.55.4              11.34.0

Flower length (in.)    1.30.2               1.70.1

Flower width (in.)     1.70.3               2.30.2

Pedicel length (in.)   1.20.3               1.00.1

Percent bud drop       6.411.2              6.56.1

Leaf length (in.)      4.80.5               5.50.3

Leaf width (in.)       1.20.1               1.50.1

Pseudobulb height to
first flower (in.)     1.90.6               6.61.6

Pseudobulb height at
termination (in.)     10.01.4              17.64.0

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D. Remy Hartmann (UH1307)

D. Remy Hartmann is a hybrid of amphidiploid D. Mini Gem and D. stratiotes of the Ceratobium (Spatulata) section. Its pedigree is similar to that of D. Cathy Beck with the exception of the D. stratiotes par ent instead of D. antennatum. The cross was made on April 9, 1988, and germinated on July 5, 1988. Seedlings were transflasked on October 11, 1988, compotted in February 1989, potted in 2-inch pots in July 1989, and repotted in 5-inch plastic pots in January 1990. A few seedlings started to flower in March 1990, only 20 months after germination, but peak flowering was obtained from October through March 1990.

The characteristics of D. Remy Hartmann are presented in Table 1. The flowers are about 2 1/4 inches across with relatively narrow sepals and petals. The petals are purple (RHSCC 78A) and the sepals are lighter purple (RHSCC 78B ) with white edges and reflexed. Due to the influence of D. stratiotes, the plants are taller than D. Betty Nakada. Pseudobulb height at first flower was about 6.5 inches, and after peak flowering in April 1991 was only 9.1 inches. Two years later the average height was 17.6 inches, still an acceptable height as a potted plant. The pseudobulbs are sturdy and upright.

The major attributes of D. Remy Hartmann are prolific flowering, good seasonality and early flowering producing marketable plants within three years from germination. The narrow green leaves on erect pseudobulbs with numerous flower sprays make att ractive potted plants.

H. Kamemoto, haruyuki@hawaii.edu
A. R. Kuehnle, heidi@hawaii.edu
T. D. Amore and N. C. Sugii

Dept. of Horticulture

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