​Habitat and Ecology
​Dendrobium ostrinum is an epiphytic orchid native and likely endemic to New Guinea and surrounding islands. It is a member of Section Grastidium, a group characterized by their short-lived flowers and thin stems. It grows as an epiphyte on trees in the hot, wet lowland and hill forests up to elevations of about 1,000 metres. Its habitat is characterized by high temperatures and very high humidity year-round with abundant rainfall, meaning the plant has no prolonged cool or dry rest period in its natural environment.
​Description
​This orchid is a small to medium-sized, sympodial perennial that forms dense clumps of slender, cane-like stems that are elongated and leafy along their length. The leaves are typically oblong-lanceolate and leathery. The plant is primarily characterized by its flowers, which emerge from the nodes along the stem in very short, few-flowered clusters (racemes). The individual blooms are small to medium-sized and are often described as deep purple. A defining characteristic of its section is the ephemeral nature of the flowers; the individual blooms are short-lived, lasting only a day or two. However, they are produced in rapid succession from multiple nodes, ensuring the plant has an extended period of intermittent blooming. The lip (labellum) is typically funnel-shaped and prominently marked.
​Cultivation
​Dendrobium ostrinum is a warm-growing orchid that requires constant heat and moisture. It is best suited for a warm greenhouse, vivarium, or highly humid cabinet in the UK. It needs bright, filtered light and should be shielded from direct, scorching midday sun. Use an open, fast-draining epiphytic mix of coarse bark, charcoal, and perlite, or grow it mounted on cork. The medium should be kept moist year-round and must not be allowed to dry out completely.
​Optimal Daytime Temperature: 24-32 C (75-90 F)
​Optimal Nighttime Temperature: A high minimum temperature is required, ideally 18-20 C (64-68 F).
​Very high humidity (70-85%) and strong air circulation are essential. Feed regularly (weekly) during the growing season with a balanced, dilute liquid orchid feed. It does not require a dry rest.
​Unique Features
​This orchid is a unique collector's plant from New Guinea, prized for its ability to produce successive bursts of its small, pale flowers over a long blooming season, a characteristic trait of the Grastidium section. Its vigorous growth and continuous blooming cycle make it a rewarding specimen for the dedicated warm-growing enthusiast.
​Specifications
​Plant Size:  younger plants raised from seed and growung nicely on mounts. See picture.
​Plant Family: Orchidaceae
​Plant Passport: A Dendrobium ostrinum B 140084 C [user input] D GB