Caleana
Caleana
Caleana, commonly known as duck orchids, is a genus of terrestrial orchids found in Australia and New Zealand. These orchids are distinctive for their single, dull-colored, inconspicuous flowers with an unusual, insect-like labellum that mimics female thynnid wasps. This mimicry is crucial for their pollination by male thynnid wasps, which are lured by pheromones emitted by the flower.
Key Facts
- ›Caleana are terrestrial, perennial, deciduous herbs typically found in sandy soil or woodland habitats.
- ›They possess a single, linear to egg-shaped leaf that develops near the base and withers late in the flowering season.
- ›The flowers are inconspicuous and dull-colored, featuring a unique, insect-like labellum on a sensitive stalk.
- ›Pollination is achieved by male thynnid wasps, attracted by pheromones, which become trapped in the flower's labellum and column mechanism.
- ›Species are distributed across Australia (all states except Northern Territory) and one species extends to New Zealand.
- ›The genus name Caleana honors George Caley, an early collector of Australian flora.
Duck Orchids
Terrestrial
Dull-Colored, Brownish Maroon, Black, Maroon, Greenish
Spring
Male Thynnid Wasps
About Caleana
What are Caleana?
Caleana, commonly referred to as duck orchids, constitutes a genus of flowering plants within the orchid family, Orchidaceae. These plants are found natively in Australia, with one species extending its range to New Zealand. The genus is recognized for its terrestrial growth habit, typically featuring a single, inconspicuous leaf and one or a few dull-colored flowers.
Description and Unique Features
Duck orchids are perennial, deciduous herbs characterized by a dark red, oval-shaped tuber and fine, inconspicuous roots. They produce replacement tubers known as "droppers" at the end of long, root-like stolons. During the growing season, a single, linear to egg-shaped leaf emerges, which folds lengthwise and may display purple markings. This leaf typically withers late in the flowering season. The flowering stem is wiry and brownish maroon, bearing one to a few flowers on short stalks. The flowers themselves are non-resupinate and glabrous. A key characteristic is the highly modified labellum, which is insect-like and attached to the flower by a sensitive stalk. This labellum is held above the flower in a "set" position and is connected by a flexible "claw" that bends under the weight of a pollinating insect.
Pollination Mechanism
The pollination mechanism of Caleana orchids is particularly noteworthy. The labellum is designed to trap visiting insects, specifically male thynnid wasps, which are attracted by pheromones emitted from glands on the labellum. When a wasp lands on the labellum in an attempt to copulate, the labellum rapidly flips downwards, trapping the insect between itself and the column wings. This action forces the insect to come into contact with the sexual parts of the column, allowing pollinia to adhere to its back. Subsequent visits to other duck orchids by the same wasp lead to pollination.
Distribution and Habitat
In Western Australia, duck orchids are commonly found growing in sandy soil in proximity to areas that are swampy during winter, often sharing their habitat with other orchid genera like Leporella, Drakaea, and Pyrorchis. In eastern Australia and New Zealand, species such as Caleana major and Caleana minor inhabit woodland, damp heath shrubland, and grassland environments. They can sometimes be found on rocky slopes, in gravelly soil, or even along road verges.
Taxonomy and Naming
The genus Caleana was first formally described by Robert Brown in 1810. The genus name honors George Caley, an early collector of Australian flora. There has been ongoing discussion regarding the taxonomic classification of Caleana and its relationship with the genus Paracaleana, with some research suggesting they may be congeneric, although some authorities continue to recognize them as separate genera.
Source: Wikipedia ↗
Frequently Asked Questions
What are duck orchids?
Duck orchids, belonging to the genus Caleana, are a group of terrestrial orchids native to Australia and New Zealand. They are characterized by their single leaf and inconspicuous, dull-colored flowers that have a distinctive insect-like appearance.
How are duck orchids pollinated?
Caleana orchids are pollinated by male thynnid wasps. The flowers emit pheromones that attract these wasps, and when a wasp attempts to mate with the labellum, it is trapped between the labellum and the column, facilitating pollination.
What is the habitat of Caleana orchids?
Their habitats vary, but they are often found in sandy soils near swampy areas, particularly in Western Australia. Other species grow in woodland, damp heath shrubland, and grassland, sometimes on rocky slopes or in gravelly soil.
What makes the flower of a duck orchid unique?
The most distinctive feature is the labellum, which is highly modified to resemble an insect. It is attached by a sensitive stalk that allows it to flip downwards, trapping visiting insects and ensuring contact with the flower's reproductive parts.
Where are duck orchids found?
Duck orchids are found across Australia, with most species occurring in Western Australia. One species, Caleana major, is found in eastern Australia, and another, Caleana minor, occurs in both eastern Australia and New Zealand.
Related Orchid species
Leptotes
Leptotes is a genus of nine small orchid species native to the dry jungles of south and southeast Brazil, Paraguay, and Argentina. These epiphytic plants are characterized by their thin, terete leaves and delicate, often showy flowers, some of which are used as a vanilla substitute. While some species are widely cultivated, many remain rare and recently described.
Leporella
Leporella fimbriata, commonly known as the hare orchid or fringed hare orchid, is the sole species within the genus Leporella in the Orchidaceae family. It is endemic to mainland southern Australia and is distinguished by its unusual labellum, lack of hairy leaves, and unique pollination mechanism involving bull-ants. This terrestrial orchid typically blooms from March to June.
Appendicula
Appendicula, commonly known as stream orchids, is a genus of flowering plants in the Orchidaceae family. These orchids are found in tropical and subtropical Asia, extending to the western Pacific. They are distinctive for their many flat, often twisted leaves and small, resupinate white or greenish flowers with fused lateral sepals and labellum at the base of the column.