Dendrobium speciosum aka Rock Lily

Dendrobium speciosum is an evergreen orchid from eastern and southeastern Australia. It belongs to the orchid family, Orchidaceae. Common names include rock lily orchid and New South Wales rock lily. In the wild, it grows on trees or rocks. These habits make it an epiphyte or lithophyte. Its native climate is subtropical.

This orchid forms clumps with upright or spreading stems. Garden plants reach about 1.6–3.3 feet [0.5–1 metre] tall. Their spread reaches 3.3–4.9 feet [1–1.5 metres]. Plants take five to ten years to reach full size. The thick, swollen stems are called pseudobulbs. Each can reach about 1.5 feet [0.45 metres] tall. They have broad bases and two to five leaves near their tops. The oval leaves are firm, green, and leathery. Large clumps develop as the plant ages.

Long flower sprays rise from the pseudobulbs in late winter and spring. Each cluster can hold up to 100 small, scented flowers. The blooms are creamy white. Chicago Botanic Garden lists flowering from January through April. It also records that the flowers attract butterflies. The flower display makes this orchid useful as a specimen. The RHS recommends it for homes, conservatories, and greenhouses. Chicago also lists it for beds and borders.

Give the roots a bark-based orchid mix that drains well. Add perlite, moss, or coir to the mix. Keep the roots slightly confined rather than using an oversized pot. Avoid frequent disturbance of the roots. Provide dappled shade and higher humidity in spring and summer. In autumn and winter, choose a bright, cool room. Reduce water and feed during this cooler period. Resume care as warmth brings flowers and new growth. The RHS rates its hardiness H1C, allowing outdoor summer use in suitable warmth. Its listed temperature band is 41–50°F [5–10°C].

Scale insects, aphids, mealybugs, and red spider mites may attack it. The RHS reports few disease problems. Routine pruning is not needed; remove faded flowers as needed. Keep canes unless they have shrivelled completely. Divide mature plants when they outgrow their pots. Older canes may also form small side plants called keiki. Pot these in sphagnum once roots reach 0.8 inches [2 centimetres]. Raising plants from seed requires controlled laboratory conditions.