Blechnum gibbum (Blechnum gibbum)
Blechnum gibbum is an evergreen, small tree-fern-like upright fern with a trunk-like erect rhizome.
Overview
Blechnum gibbum is an evergreen, small tree-fern-like upright fern with a trunk-like erect rhizome.
Origin and habitat
Sources differ on its native range: it occurs on southwestern Pacific islands around New Caledonia and Vanuatu, while some sources also include Fiji in its distribution or native range. It is reported from tropical, relatively warm and humid environments.
Characteristics
Sources differ, with few sources supporting a mature height of about 50–100 cm; its mature spread is reported to be about 50–100 cm, based on few sources. The glossy, thick, leathery, bright green leaves cluster at the top of the upright stem; vegetative leaves are obovate and deeply pinnately divided with numerous pinnae, while fertile leaves are similar in size but have distinctly narrower pinnae. It has an erect rhizome.
Light
It grows in partial shade or bright filtered, indirect light, and outdoors can grow from full shade to partial shade or part sun.
Watering
Keep evenly moist in a moist but well-drained medium, avoiding dry conditions; it prefers a moist, humus-rich environment.
Humidity and airflow
It prefers high humidity and has a high humidity need. It is reported to need good airflow.
Temperature and dormancy
Sources differ, with few sources supporting a minimum temperature of about 15 °C. It is generally classed as RHS H1A. It is tender.
Growing medium and mounting
Use loam or a humus-rich medium that stays moist but drains well, with acidic to neutral conditions.
Propagation
It is reported to be propagated from spores in summer or by division, although divided plants may take some time to re-establish growth. The sori are reported to form long linear rows on both sides of the midrib of the lobes or pinnae.
Common problems
It is generally reported to have few notable pests and few notable diseases, but to be sensitive to dry conditions. It is sensitive to low temperatures and frost; outdoor cultivation requires a very sheltered, warm position, while protected greenhouse or indoor cultivation is more suitable in temperate regions.
Identification
Blechnum gibbum has a conspicuous upright, trunk-like rhizome with leaves clustered at its apex, including vegetative leaves and narrower fertile leaves; its sori are long and linear, arranged along both sides of the pinna midrib.
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