Dendrobium lindleyi (syn. aggregatum) - an epiphytic species, distributed from northeast India, covering Indochina and Thailand (where it grows on the branches of deciduous trees in mountainous areas, but also in southern and south-central regions at altitudes of 650 - 1400 m), Sikkim, Bhutan, Burma, Laos, Vietnam, and southwest China, Dendrobium aggregatum enjoys a perhaps undeserved reputation among collectors, with supporters claiming the ease of cultivation and flowering of the species, but also vehement opponents who argue the difficulty of obtaining blooms, or even the difficulty of its cultivation.
The genus name, already explained in previous posts, I would like to draw attention to the specific name, aggregatum, which means aggregated, gathered, grouped, and most likely refers either to the arrangement of the pseudobulbs as dense, crowded masses, or to the flowers in abundant clusters. The valid species name, Lindleyi, represents the Latin genitive of the name of the great English orchidologist, simply meaning "Lindley’s dendrobium", dedicated to the scientist as a tribute by botanist Ernst Gottlieb von Steudel in 1840, when the latter described this species.
Valid synonyms are: Callista aggregata, Dendrobium aggregatum, Dendrobium alboviride var. majus, Dendrobium lindleyi var. majus, Epidendrum aggregatum.
Specimens of this species appear starting at altitudes above 500 m, but there are known cases where they successfully inhabit warmer or temperate environments, due to the remarkable adaptability of this taxon to climatic conditions, yet regardless of the preferred growth mode, the species will always require a high amount of light radiation, water, and a rest period during winter.
A miniature species of the genus, with a total height of 10 - 20 cm, with short pseudobulbs, approximately 5 - 10 cm long, thick, slightly wrinkled, angular, intended for storing water reserves and nutrients, crowded together at the base, with slightly pointed tips - forming clusters, aggregations, which give the species its name.
In general, they are covered by a fibrous sheath, similar in texture to paper, called sarong (the name of a traditional garment in the Philippines, Malaysia, Indonesia), serving to protect new growths, whose removal is not recommended unless fungal, bacterial, or entomological infections or infestations are suspected. Due to the fact that after exposure to strong sunlight the pseudobulbs acquire a reddish tint, from the accumulation of anthocyanins, which protect against sunburn, gaining an appearance similar to dried figs.
In the case of dividing the plants, it is necessary to ensure that each resulting division consists of at least 5 - 9 bulbs. The leaves of Dendrobium aggregatum specimens are short and thick, hard, singular, inserted apically on each pseudobulb, with a deeply grooved central vein, relatively elliptical and somewhat rigid, flexing them is not recommended.
The coloration is dark green, but their color lightens with exposure to the sun, a common aspect found in species of the genus Dendrobium. However, the yellow color of the leaves is a sure indicator signaling the onset of health problems.
The roots are generally thin and white, with a somewhat hard texture, the growing tips being transparent and green, and also particularly fragile, an aspect that requires careful handling of the plants when replanting in other media and containers.
The flowers are very delicate, 2.5 - 5 cm in diameter, white, yellow, or dark orange in color, with tendencies to intensify the color as they mature, pendulous, arising from a branched and thin floral stem that emerges from the base of the pseudobulbs and develops fully over several weeks, ultimately rewarding passionate and patient growers.
The labellum is generally orange or yellow, darker at the base. The flowers, with proper care and ensuring adequate humidity, persist on the stems on average between one week and a month. They are flat, without a prominent labellum, carrying a subtle honey aroma, quite difficult to detect from a distance, but noticeable up close, especially in the morning and evening hours, the scent activating in low light conditions.
Flowering occurs in winter and spring. The inflorescences will carry 10 - 20 flowers, but young plants may have fewer. Flower spikes will not bloom again, so it is necessary to cut them after the flowers dry and fall.
Planting will be done using medium-grain pine bark, dried fern, or even teak wood fragments. Mounting on plaques is preferred, as this method allows the roots to dry completely between waterings and ensures air circulation; species of this genus detest water stagnation around the roots. When mounting, it is recommended to add a layer of sphagnum moss between the support plaque and the plant to avoid too rapid dehydration. Tying can be done with fishing nylon, because, unlike metal wire, it does not interact with the environment and does not degrade in the presence of water. The ties can be removed after the plant attaches to the substrate with the help of its roots. In the case of mounting in containers, a coarse-grained substrate will be used, which dries quickly and ensures water drainage. Dendrobium species do not appreciate intervention at the root level.
The light radiation necessary for good development will be abundant, but diffuse light, not direct, is preferred. Its level will be in the range of 35000 – 40000 lux, similar to most Cattleya species. When the pseudobulbs take on a reddish tint, it is a sign that the plant is receiving as much light as it needs, and keeping that location is preferred, unless sunburn appears. During the winter rest period, the light energy supply will be maintained at the same level.
The recommended temperature for this species is 26 - 28 °C during summer days, and 19 - 20 °C at night. During spring, the daytime temperature will be 30 - 31°C and the nighttime temperature 12 - 19 °C, with daytime values corresponding to the range of 25 - 28 °C and 9 - 10 °C at night.
Watering, in the case of plants mounted on plaques, will be abundant, but atmospheric conditions, specifically humidity and temperature, will be taken into account. As a general rule, complete or prolonged drying will not be allowed. In the case of plants mounted in pots or similar containers, it is recommended to allow the substrate to dry completely before watering again.
Relative humidity for this species is 80 - 85% during the growing season, but in winter and spring it is necessary to reduce it to 60 - 65%. Fertilizations will be done regularly, but under no circumstances more frequently than once a week.
Fertilizer should not be applied to sick plants or those with dry roots, as it can cause root burn. It is recommended to use a dose of 50% of the normal indicated concentration, as well as one with added nitrogen, followed by one with added phosphorus from mid-summer to the end of autumn. The winter rest will consist of exposure to temperatures of 10 - 15 °C at night, with slight daytime increases.
Plants can tolerate light frost, but allowing such events is not recommended. Watering will be gradually reduced and fertilization completely stopped during the rest period, with watering resuming only if excessive wrinkling and shriveling of the bulbs is observed, but it should be noted that moderate wrinkling of the bulbs, as well as partial leaf drop, are normal phenomena typical of the species. Dendrobium lindleyi will bloom even if the winter night temperature is 16 °C, if a rest period without water is ensured, but it will benefit more from one at 10°C.
Plants that are not given this cold and dry rest period will develop keiki instead of flowers. It is possible to completely stop watering during the winter - however, plants will be healthier if during winter, for the most part, the substrate is allowed to dry completely between waterings and if these drying periods do not last too long. In the 1-2 months after the end of winter, the substrate will be allowed to dry completely between waterings and the drying period until the next watering will be longer. However, spraying can be done in the morning to protect the plants from complete drying.
The rest period with reduced water administration will last until the flower stems reach a length of approximately 2.5 cm. Fertilization will be stopped until spring arrives, when normal watering will resume. The light radiation level will be kept as high as possible.
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