Dendrobium bigibbum aka Cooktown Orchid

Dendrobium bigibbum requires bright indirect light, significantly brighter than Phalaenopsis orchids. Provide 2,000 to 5,000 fc light intensity in a west or south-facing window. Direct morning sunlight is beneficial and helps promote flowering, but protect from harsh afternoon sun. In spring and summer provide indirect light, then move to a bright room in autumn and winter.

Dendrobium bigibbum is a warm-growing thermophilic orchid requiring minimum daytime temperatures of 75-78°F (24-26°C) and nighttime temperatures of 62-66°F (17-19°C). Temperatures should not drop below 16°C (61°F). This species thrives in consistently warm conditions year-round and cannot tolerate frost or cold temperatures.

Dendrobium bigibbum produces cylindrical pseudobulbs (cane-like stems) that range from 20-120 cm (8-48 inches) in length and 15-20 mm wide. Mature plants typically reach 40-122 cm in height with a moderate spread. Each pseudobulb carries 3-12 dark green lance-shaped leaves on the upper half. The plant exhibits moderate growth rate with sympodial growth habit, producing new pseudobulbs annually from the rhizome.

Dendrobium bigibbum blooms from February to July (primarily March-July during the dry season), though cultivated plants may flower multiple times per year. Arching flowering stems up to 30 cm long emerge from upper nodes carrying up to 20 bright pinkish-purple flowers. Individual flowers are 4-7 cm in size and exceptionally long-lasting, persisting for 1-3 months. The flowers are fragrant and resemble moth orchids.

Four varieties are recognized: D. bigibbum var. bigibbum (mauve butterfly orchid with white spot on labellum, found on Cape York Peninsula and New Guinea), var. superbum (Cooktown orchid with largest flowers but no white spot, occurring near Cooktown), var. compactum (narrow distribution lithophyte in wet tropics), and var. schroederianum (variably colored flowers from Tanimbar Islands). Award-winning cultivars include 'Col', 'Judy', 'Samantha Louise', and 'Tozer Stripe'.

Propagate through keikis (plantlets) that develop on older canes - remove and pot when roots are at least 2 cm long in sphagnum moss. Division is possible when plants overgrow their pot; ensure each division has at least 3-4 healthy pseudobulbs. Seed propagation requires sterile laboratory conditions and is not practical for home growers. Natural aerial growths can be pruned off and potted up once they have developed roots.

Minimal pruning required for Dendrobium bigibbum. Remove spent flower stems by cutting right back to the base of the plant. Do not cut canes unless completely shriveled - old leafless canes can still produce flowers. Only remove the oldest canes if there are at least three younger, thick, leaf-bearing canes on the plant, as old canes store nutrients and support the plant.

Repot every 2-3 years in spring after blooming finishes, or when the potting mix begins to break down. Use the smallest pot possible and medium-grade bark-based orchid mix with added perlite, moss, or coir. Dendrobiums grow best when roots are slightly restricted, so avoid over-potting. Allow as many roots as possible to grow outside the pot as they need air circulation for healthy growth.

Common pests include mealybugs, scale insects, spider mites, aphids, and thrips - treat with insecticidal soap or neem oil. Fungal diseases like Phyllosticta leaf spot cause circular yellow spots that turn black with weblike patterns. Root rot and bacterial soft rot occur from overwatering, showing mushy roots and foul odor. Watch for collar rot, botrytis petal blight, black rot, and anthracnose, especially in high humidity without adequate air circulation.

Yellowing leaves signal several issues: overwatering causes root rot with mushy roots and foul odor, while underwatering shows shriveled pseudobulbs and dry medium. Insufficient light exposure leads to pale, yellowing foliage. Nitrogen deficiency robs leaves of green color. Temperature fluctuations and low humidity (below 60%) cause leaf tips to yellow and brown. Check watering habits, light levels, and environmental conditions to diagnose the cause.

Dendrobium bigibbum can be grown outdoors year-round in USDA hardiness zones 10-12 (coastal California, Florida, southern Texas). It requires a frost-free climate with high humidity and stable temperatures - even brief frost exposure can harm the plant. Native to tropical Australian and New Guinea forests growing on trees or rocks up to 500m elevation. In cooler zones, grow in greenhouse or bring indoors before temperatures drop below 16°C (61°F).

Yes, Dendrobium bigibbum produces fragrant flowers. The variety compactum (lithicolum) is specifically noted for its wonderful fragrance. The scent adds to the ornamental appeal of the long-lasting blooms, though specific scent descriptions vary among individual plants and varieties.