A complex, epiphytic, multispecific hybrid, created through successive additions of botanical species, Dendrobium Stardust has several color varieties, among which the most common in specialized trade are Firebird and Chiyomi, while the Rainbow Dance and White Swan varieties are rarer, at least in Romania..
The most striking differences between these varieties are the floral colors, where Dendrobium Chiyomi will have a predominantly yellow or pale yellow color, Dendrobium Firebird will be intensely orange, Dendrobium White Swan, as the name suggests, will have a solid white color with slight occasional pale pink shades arranged centrally, and in Dendrobium Rainbow Dance the violet-lilac color will dominate – with a white labellum and gradient shades toward white in the basal area of the petals and sepals.
In the ancestry of this hybrid, as spectacular as it is, belonging to the Dendrobium section, yet as commercially common and easy to care for, there are 5 botanical species with progressively relative weights, revealing the gradual hybridization process, in which the insertion of one botanical species into the family tree alongside a hybrid was chosen. The only exception is the second stage of hybridization, where the authors prefer crossing two primary hybrids. Although this taxon is often referred to in specialized trade as a variety or a hybrid of the noble species, the species percentage clearly indicates the dominance of the unicum species, present at 50%, as it is introduced in the formula at the last crossing. This is followed by the species Dendrobium moniliforme at 25%, then the species Dendrobium nobile, which totals 12.5%, being equally present in the two primary hybrids crossed in the second stage of hybridization, namely ainsworthii (Den. heterocarpum (6.25%) X Den. nobile (6.25%)), and Wiganiae (Den. nobile (6.25%) X Den. signatum (6.25%)). This hybrid was created in 1986 by Nobuyuki Asai and his team at Asai Daikeikan Co Ltd. in Aichi-Ken (Japan). Crossings began in 1986, but the patent for this hybrid was registered in the United States of America only in 2000.
In fact, the chronology of events is much more complex, and we will briefly recount it only to illustrate the efforts and long time generally behind the launch of a new hybrid. In 1980, the species Dendrobium unicum was crossed with the multigeneric hybrid Dendrobium Unkon, resulting in plants that were placed in flasks starting in October of the same year. The specimens were grown to maturity, when they flowered, and the new grex epithet Stardust was registered at the RHS (Royal Horticultural Society), the International Orchid Hybrid Registration Authority, in 1986 by N. Asai. From this group of plants, the Firebird hybrid was selected and vegetatively propagated by isolating those plants that exhibited the desired characteristics in terms of flower number, compact growth, and rapid growth. Meristem culture techniques were applied to this batch, and after a long testing period lasting until 1993, when the retention of characteristics by reproductive products was noted, the batch was tested for immunity against Dendrobium virus, Dendrobium Thabdo virus, and Tomato spotted wilt virus, showing favorable results. The plants were maintained in greenhouses in Aichi-ken, where the minimum temperature did not drop below 13 degrees.
The colors recorded for this hybrid are relatively approximate, largely depending on cultivation techniques applied, such as exposure to light radiation and type of fertilization, but without inducing changes at the genotype level. The aspects that distinctly differentiate the Firebird cultivar from the related, unpatented Chiyomi cultivar have been observed successively, consisting of the fact that in Firebird the lateral petals are twisted in the opposite direction compared to the petals of the Chiyomi cultivar, and the red-orange checkered area present in Firebird differs significantly from the color pattern of Chiyomi.
In terms of growth rate, Dendrobium Firebird specimens grow extremely fast, producing plants suitable for sale in the spring, requiring 12–14 months to produce flowering specimens from stem segments. The typical minimum height of plants at flowering age for Stardust is approximately 35–40 cm. The typical flowering season is from October to May, peaking in March, although flowering is often noted outside this season as well. Flowers persist on stems for 6 to 8 weeks. The flowers are simple, monoecious, bearing both male and female sexual organs on the same flower.
The raceme is medium-sized and always upright, always including two to three flowers inserted on short pedicels. The leaf shape is mostly elongated and elliptical to ovate, with an uneven blunt apex oriented horizontally. Leaves do not persist on pseudobulbs for more than 2-3 years; the absence of leaves on a bulb can successfully indicate their minimum age. Each pseudobulb has 7-10 leaves with entire margins. Pseudobulbs viewed from the front are linear, long, segmented, growing relatively aggregated, and round in cross-section, rarely exceeding 1.5-2 cm in thickness. The length of the pseudobulbs is strongly influenced by light availability; the stronger the light, the shorter the pseudobulbs.
Propagation is easily done from keikis, which the plant frequently and naturally produces without the need for stimulation. These usually develop from the lower bracts of the inflorescences, and the resulting plantlets can be detached from the mother plant after root development. To stimulate root growth, it is recommended to superficially wrap the junction site with moist sphagnum moss.
Ideal lighting for this hybrid should be abundant but without direct sunlight, which can cause burns on the leaves and pseudobulbs. If the light is sufficiently abundant, the leaves will show a yellow-green coloration, sometimes mistaken by inexperienced enthusiasts as a disease.
Growth temperature can vary, but the hybrid belongs to a rather mixed regime, with the following recommended temperatures: during summer, exposure to temperatures above 32 degrees should be avoided, and in winter, minimum temperatures should not drop below 5-18 degrees. For successful indoor cultivation, a day-night temperature difference of about 4-6 degrees is recommended.
In terms of humidity, this taxon does not require high values, which can range from 40 to 60%. Lower values cause growth inhibition, yellowing of the leaves, and premature leaf drop. The higher the chosen growth temperature, the more necessary it will be to increase the atmospheric humidity accordingly, while ensuring this thermal/hydric increase is combined with an adequate level of ventilation to prevent fungal diseases.
The growing substrate is recommended only when using narrow pots, often suspended, with a preference for solid ceramic ones that provide stability to plants after excessive elongation of pseudobulbs, which can otherwise cause pots to tip over. This hybrid shows no special preference for substrate types, surprisingly growing well in peat or sphagnum moss substrates, minimal granule bark, or coconut fiber.
Frequent repotting is not necessary, and is only recommended if excessive substrate compaction is noticed, dramatic changes in chemistry (pH), or if the plants outgrow their pots significantly. The recommended repotting period is during spring, when new growths have reached 5 cm in size and have their own roots.
Watering will be frequent and abundant during the growth period, but care should be taken to ensure efficient drainage to prevent water stagnation in the substrate and the development of mold and root rot. The substrate must dry out thoroughly between waterings.
Fertilizations should be done every 2-3 weeks during the growth period, at the concentration indicated on the containers. It is also recommended to apply additional foliar fertilizer, at a high dilution of 10-25% of the recommended dose, applied by spraying. The ideal fertilization method will alternate between these two techniques.
This hybrid requires a well-defined rest period to stimulate re-flowering. This begins once the young pseudobulbs mature, when they complete their growth, showing a rounded apical area with a single leaf expanded at the apex. At this point, a slight decrease in humidity and temperature levels will be chosen, along with stopping fertilization. The temperature should not rise above 16-18 degrees during the day and 10 degrees at night. Sometimes it is advisable to stop watering altogether or replace it with light sprays repeated monthly. Once new flower spikes appear, the rest period will end, and the current routine will be resumed.
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