Corybas cheesemanii aka Cheesemans Spider Orchid

Corybas cheesemanii is an expert-level plant that is extremely difficult to cultivate and should not be removed from the wild. It requires specific mycorrhizal fungi for germination and growth, precise environmental conditions including deep moist leaf litter substrate, full shade, high humidity, and cool temperatures. Even specialist orchid growers find this and other Corybas species extremely challenging to maintain in cultivation.

Corybas cheesemanii requires constantly moist conditions but should never be waterlogged. In its natural habitat, it grows in deep, moist, semi-rotted leaf litter that maintains consistent moisture. If attempting cultivation, maintain high humidity around 70-80% and keep the growing medium consistently damp without allowing standing water, which can cause tuber rot.

In nature, Corybas cheesemanii grows in deep, moist, semi-rotted leaf litter, often partially or completely buried within the substrate. For cultivation attempts, a well-draining terrestrial orchid mix rich in organic matter is recommended, comprising bark, peat moss, perlite, and leaf mould. The substrate must retain moisture while allowing excess water to drain freely.

Corybas cheesemanii requires full shade and grows naturally in 'dark, very shaded sites' on the forest floor beneath kānuka and beech trees. Direct sunlight should be completely avoided as it will damage this shade-adapted orchid. In cultivation, bright indirect light is too intense—this species needs conditions mimicking the deeply shaded forest understory.

High humidity of 70-80% is essential for Corybas cheesemanii. The species naturally grows in moist forest environments with consistent atmospheric moisture. Low humidity will cause the single delicate leaf to desiccate. In cultivation, maintaining high humidity while ensuring good air circulation to prevent fungal problems is challenging but necessary.

Corybas cheesemanii is a cool to intermediate growing orchid, preferring temperatures between 10-25°C (50-77°F). As a New Zealand endemic found from coastal to montane habitats up to 1000m elevation, it is adapted to cool, temperate conditions. The species is winter to spring growing and flowers during the cooler months (May-September in the Southern Hemisphere).

Propagation of Corybas cheesemanii is extremely difficult and the species should not be removed from the wild. Like all orchids, seeds require symbiotic mycorrhizal fungi to germinate, and the specific fungal partners for this species are not well characterised. Division of mature plants is theoretically possible but risky. Tissue culture propagation requires specialised laboratory facilities and expertise.

Corybas cheesemanii is a diminutive orchid, reaching only 25mm (1 inch) in height when flowering, though the fruiting stem can extend up to 220mm. The single heart-shaped leaf measures 10-20mm long. The plant has a slow growth rate and deciduous habit, dying back after flowering and fruiting before re-emerging from tubers. Tubers can produce lateral roots extending up to 200mm away.

Corybas cheesemanii flowers from May to September (autumn through winter in New Zealand). Each plant produces a single flower that varies from dark pink through greyish-white with purple specks to completely white. The distinctive helmet-shaped (galeate) dorsal sepal arches over the labellum, and paired spurs project from the base. Individual flowers last approximately 23 days, and about 78% of plants in a population will flower.

Corybas cheesemanii is pollinated by fungus gnats (Mycetophilidae), particularly male gnats in the genus Mycetophilia. The orchid employs brood-site deception, mimicking the appearance and possibly scent of mushrooms to attract female fungus gnats seeking oviposition sites. Approximately 25% of flowers set seed naturally, while about 50% can achieve fruit set through autonomous self-pollination.

Corybas cheesemanii is endemic to New Zealand, meaning it occurs naturally nowhere else in the world. It is found on Manawatāwhi/Three Kings Islands, the North Island, South Island, and Chatham Islands. The species occurs from coastal to montane habitats up to 1000m elevation, typically in tall scrub and forest beneath kānuka and beech trees.

Corybas cheesemanii is deciduous and follows a distinct seasonal cycle. It grows actively during winter and spring (May-November in the Southern Hemisphere), flowers in autumn-winter (May-September), then produces fruit (November-January) before dying back. During dormancy, tubers remain underground and should be kept barely moist. Active growth resumes as temperatures cool in autumn.

Corybas cheesemanii can only grow outdoors in conditions closely matching its native New Zealand habitat—cool temperate climate, deep shade, high humidity, and moist leaf litter substrate. Outside New Zealand, outdoor cultivation is extremely unlikely to succeed. The species is not frost-hardy and cannot tolerate hot summers or dry conditions. This orchid is best appreciated in its natural habitat rather than attempted in cultivation.

Common pests affecting Corybas species include spider mites, aphids, and slugs or snails which are attracted to the succulent tubers and soft leaf tissue. Fungal infections are a significant risk, particularly in conditions of poor air circulation combined with the high humidity these orchids require. Maintaining good airflow while ensuring high humidity is essential for disease prevention.

There is no verified data on the toxicity of this plant in the records of Ploi. If any person, including yourself, a family member, or a pet, consume plant material with an uncertain toxicity level, it is advisable to seek the advice of a healthcare expert.