Spider orchids facts for kids
Caladenia, also known as spider orchids, is a group of about 350 different kinds of plants in the Orchid family. These orchids grow in the ground and have a single hairy leaf and a hairy stem. Most spider orchids have a special lip-like petal called a labellum that is fringed or has teeth. They also have small bumps called calli on this labellum.
The flowers of spider orchids are designed to attract specific insects for pollination. Scientists divide these orchids into three main groups based on their flower shape: spider orchids, zebra orchids, and cowslip orchids. While you can find them in other countries, most spider orchids live in Australia. Western Australia alone has 136 species, making it the state with the most types of these beautiful orchids.
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What Spider Orchids Look Like
Spider orchids are ground-dwelling plants that live for many years. They lose their leaves each year and grow new ones. They have a few small roots and a special underground storage part called a tuber. This tuber is partly covered by a protective layer. Each year, the tuber grows two "droppers" which will become new tubers for the next year.
At the bottom of the plant, there is one hairy leaf. This leaf is usually medium to large, thick, or tough. It can be shaped like a spear or an oval, but it's always a single, simple leaf without any cuts or jagged edges.
Spider orchids usually have one to eight flowers on a stalk. The three outer leaf-like parts (called sepals) and the two side petals are separate and look similar in size and shape. In some types, the sepals or petals (or both) have narrow tips that end in a club-like shape.
Like other orchids, one petal is very special and forms the central labellum. This labellum is usually divided into three parts, and each part often has a fringed or toothed edge. The middle part of the labellum has small, stalked, or button-like bumps called calli, which are often arranged in rows. The parts of the flower involved in reproduction are joined together in a structure called the column, which has wing-like parts on its sides.
Most spider orchids bloom in early spring. However, some, like the winter spider orchid, flower in other months. After flowering, the plant produces a dry seed pod called a capsule. This capsule opens up to release many tiny seeds, sometimes up to 500!
How Spider Orchids Got Their Name
The first spider orchid plants were collected in Australia by Joseph Banks in 1777 and by Archibald Menzies in 1784. The first formal description of a spider orchid, then called Arethusa catenata (now known as Caladenia catenata), was made by James Edward Smith in 1805.
The group of plants known as Caladenia was officially named by Robert Brown in 1810. He described 15 different species of Caladenia at that time. Brown collected these plants while he was exploring Australia with Matthew Flinders. He spent over three years studying plants in Australia.
The name Caladenia comes from two Ancient Greek words: kalos, meaning "beautiful," and aden, meaning "a gland." This name refers to the colourful labellum of the flower.
Scientists have studied the DNA of these orchids to understand how they are related. Based on these studies, some orchids that were once in different groups, like Glossodia and Cyanicula, are now considered part of the Caladenia family.
Spider orchids are often grouped by how their flowers look. Some have long, narrow sepals and petals, like the white spider orchid. Others have short sepals and petals that hang close to the stem, such as the zebra orchid. A third group has short, spreading sepals and petals, like the cowslip orchid.
Where Spider Orchids Live
Most spider orchids are found only in Australia. However, eleven species grow in New Zealand, and one of those also grows in Australia. Two species, Caladenia catenata and C. carnea, can be found in New Caledonia, and C. carnea also grows in Indonesia.
In Western Australia, about 136 species of spider orchids grow in the south-west region. You can find them from the coast near Kalbarri all the way to the Nuytsland Nature Reserve on the southern coast. They live in many different places, from cool, damp Karri forests to coastal swamps and even dry mallee woodlands.
How Spider Orchids Attract Insects
Spider orchids are pollinated by insects, usually bees or wasps. Some species are very clever! They attract male wasps by smelling, looking, and feeling like female wasps that cannot fly. For example, the butterfly orchid (C. lobata) attracts male Thynnoides bidens wasps.
When a wasp lands on the flower, its weight pulls the labellum down. As the wasp moves up the labellum, it is tipped against the flower's column. This is where the wasp either picks up or drops off pollen. Many of these orchids are only attractive to one specific type of insect.
Sometimes, different types of spider orchids can mix and create new kinds of orchids (called hybrids). For example, C. patersonii smells like something fermenting and attracts several insect species. It can form hybrids with orchids that mimic insects, like C. lobata.
In some spider orchids, the sepals and petals (not including the labellum) are narrow and have expanded tips called "clubs." Scientists think these clubs produce the special smells that attract male wasps to the orchids that mimic female wasps. Most of these orchids don't have a smell that humans can detect, but they are very attractive to male Thynnid wasps. For some species, like C. multiclavia, it's the labellum itself that looks and probably smells like the female wasp.
Growing Spider Orchids
It has been quite hard to grow Caladenia orchids outside of their natural environment. Some people who love orchids have had a little success by growing the special fungus that the orchid needs to survive. They also carefully use fertilizer to keep the fungus and orchid healthy together. An old book from 1889, 'The Useful Native Plants of Australia', mentions that these and other orchids have edible tubers (the underground storage parts).
Images for kids
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Arrowsmith spider orchid (C. crebra)
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Clubbed spider orchid (C. longicauda) budding
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White fingers (C. chlorostyla), from New Zealand
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Several Caladenia species from Pelloe's West Australia Orchids
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C. atrovespa growing near Canberra
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Dancing spider (C. discoidea) growing near Perth
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Butterfly orchid (C. lobata) near Mount Barker
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Large white spider orchid (C. venusta)
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