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 flower size at values larger than Dawn Maree, Roongkamol Vejvarut certainly represents progress both in terms of color and 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 Dendrobium sections), all combined with 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%. Later, Roongkamol Vejvarut served as the basis for creating three 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 in the labellum's coloration.
Small to medium-sized, heat-loving but moderately so, it can reach 20 – 40 cm in height, with erect pseudobulbs bearing foliage on the upper two-thirds, consisting of leathery, oblong-elliptical, blunt 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 in diameter), have a white background color, a crystalline texture, featuring lanceolate sepals and round petals of the same length as the sepals. The labellum displays a strongly contrasting coloration, orange-red on a white background, with a ligulate shape that curves downward.
Dendrobium Roongkamol requires high levels of light radiation, between 30,000 – 40,000 lux, and mature pseudobulbs can successfully withstand direct sunlight.
Recommended daytime temperatures in the warm season range from 19–24 ℃, and nighttime temperatures from 12–18 ℃, ensuring a day/night difference of 5–9 ℃. In winter, the average daytime temperature will be between 16–21 ℃ with nighttime lows of 2–3 ℃ and a day/night difference of 10–18 ℃. In spring, daytime temperatures will rise to 23–24 ℃ and nighttime to 5–12 ℃, 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, as the plants demonstrate an amazing capacity to adapt 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, growing in pots with a mix of sphagnum moss, coconut compost, bark of 3–6 mm diameter, possibly amended with vermiculite or perlite, is recommended. Repotting is advised in early spring with the appearance of new root growth.
Watering will be moderate to abundant from late spring until early autumn but reduced during winter once new growths reach maturity.
Fertilizer should 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 resting period lasting from winter until new growth appears in spring. During this time, watering can be reduced or completely stopped, but care must be taken not to allow the plants to dry out completely. In the last month of late winter, complete drying will be allowed, resorting only to morning misting. Along with reducing watering, fertilization will also be stopped and resumed at the beginning of spring.
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