A secondary hybrid obtained by the Thai breeder Kirit Vejvarut by crossing the primary hybrid Dendrobium Dawn Maree created and registered by J. Burrows in 1983 (Dendrobium formosum as seed parent X Dendrobium cruentum as pollen parent) with one of the parents, namely Dendrobium formosum, aiming to stabilize the flower size at higher values than Dawn Maree, Roongkamol Vejvarut certainly represents progress both chromatically and in size..
Last but not least, the use of two parents from the Formosae section (formerly Nigrohirsutae) guarantees repeated, abundant, long-lasting flowering, with large flowers (probably the largest among all sections of the Dendrobium genus), all this on the background of ease of cultivation in apartment conditions, suitable even for beginners in orchid growing. The hybrid was registered with the Royal Horticultural Society on 18.07.2001 and has the following parental formula: Dendrobium formosum 75% and Dendrobium cruentum 25%. Subsequently, Roongkamol Vejvarut will be the basis for creating 3 more hybrids, namely Dendrobium Bali Sweet Heart, Dendrobium Datin Zakiyah, and Dendrobium Jairak Dawn, the last of which attracts the most attention, representing a cross with Dawn Marie.
Dendrobium Roongkamol Vejvarut inherits from formosum the large-sized flower, with a crystalline texture, and high persistence despite its fragile appearance, and from cruentum the strong contrast, with red-orange shades, of the labellum's coloration.
Small to medium-sized, heat-loving but moderately so, it can reach 20 – 40 cm in height, presenting erect pseudobulbs bearing foliage on the upper two-thirds, consisting of leathery, oblong elliptical, obtuse leaves, 9 – 15 cm long, articulated at the base with hairy (pubescent), tubular sheaths, which gave the previously known name of the section.
Flowering occurs from autumn to winter, on short stems, axillary or in the form of terminal racemes, with 1-4 fragrant flowers, emerging from the nodes near the leaf area of mature pseudobulbs. The flowers, impressively sized (8 – 15 cm diameter), have a white background color, a crystalline texture, featuring lanceolate sepals and round-shaped petals, the same length as the sepals. The labellum shows a strongly contrasting coloration, orange – red, on a white background, having a ligulate and downward recurved shape.
Dendrobium Roongkamol requires high levels of light radiation, of 30000 – 40000 lux, and mature pseudobulbs can successfully withstand direct sunlight.
Recommended daytime temperatures in the warm season will range between 19 – 24 ℃, and nighttime temperatures between 12 – 18 ℃, ensuring a day/night difference of 5 – 9 ℃. In winter, the average daytime temperature will be between 16 – 21 ℃ with minimums of 2 – 3 ℃ at night and a day/night difference of 10 – 18 ℃. In spring, daytime temperatures will rise to 23 – 24 ℃ during the day and 5 – 12 ℃ at night, with an 11 – 18 ℃ difference. All these values indicate that Roongkamol is a plant that can be easily grown on an unheated closed balcony throughout the year. It is also worth mentioning that these values are theoretical and indicative, with plants demonstrating an amazing capacity for adaptation in practice.
Optimal humidity will be 60 – 85% throughout the year, aiming for a correlation between atmospheric humidity and temperature.
Although it can be grown on bark or cork plaques, or in wooden baskets, provided adequate humidity is ensured, we consider that for ease of cultivation it is recommended to grow in pots, with a mixture of sphagnum moss, coconut compost, bark of 3 – 6 mm diameter, possibly amended with vermiculite or perlite. Repotting is recommended early spring, along with the appearance of new root growths.
Irrigation will be moderate to abundant from late spring until early autumn, but will be reduced during winter, once the new growths reach maturity.
The fertilizer will be applied weekly, at 25 – 50% of the recommended concentration. A nitrogen-rich fertilizer is recommended from spring until mid-summer, replaced by a phosphorus-rich fertilizer from late summer until winter.
For Dendrobium Roongkamol, it is especially important to allocate a rest period that will last from winter until the appearance of new growths in spring. During this period, irrigation can be reduced or completely eliminated, taking care not to allow the plants to dry out completely. In the last month at the end of winter, complete drying will be allowed, resorting only to spraying in the morning. Along with the reduction of irrigation, fertilizer application will also be stopped, resuming at the beginning of spring.
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