Green-comb spider-orchid facts for kids

Quick facts for kids Green comb spider orchid
Scientific classification
Genus:	Caladenia
Species:	dilatata

The Caladenia dilatata, also known as the green-comb spider orchid, is a special plant. In some Indigenous languages, it's called koolin. This orchid belongs to the amazing Orchidaceae family. It grows only in south-eastern Australia, which means it's endemic to that area.

This unique orchid has a single leaf and one yellowish-green flower. The flower often has pretty reddish stripes. You can find the green-comb spider orchid growing in Victoria and Tasmania. It looks a bit like other spider orchids, such as C. necrophylla from South Australia and C. concinna from New South Wales.

What Does It Look Like?

The green-comb spider orchid is a perennial plant. This means it lives for more than two years. It's also a deciduous herb, which means its leaves fall off at certain times. This plant grows from an underground tuber, which is like a storage root.

It has one leaf that is about 60 to 130 millimeters (2.4 to 5.1 inches) long. The leaf is 6 to 8 millimeters (0.24 to 0.31 inches) wide. You might see small red spots near the bottom of the leaf. Often, the leaf dries up by the time the flower blooms.

The Flower's Features

A single, beautiful yellowish-green flower grows on a stem. This stem can be 200 to 350 millimeters (7.9 to 13.8 inches) tall. The flower has reddish stripes that make it stand out.

The parts of the flower that look like petals are called sepals and petals. They have thin, thread-like tips that are 5 to 15 millimeters (0.20 to 0.59 inches) long. These tips are covered in tiny glands.

• The top sepal, called the dorsal sepal, stands upright. It is about 35 to 50 millimeters (1.4 to 2.0 inches) long. It's narrow, only 2 to 3.5 millimeters (0.079 to 0.138 inches) wide, and its tip droops down.
• The two side sepals, called lateral sepals, are also 35 to 50 millimeters long. They are about 3 to 3.5 millimeters (0.12 to 0.14 inches) wide near their base. Then they get thinner, like threads. These side sepals can be parallel to each other or even cross over.
• The petals are 25 to 35 millimeters (0.98 to 1.38 inches) long and curve downwards. They are quite thin, about 1.5 to 2 millimeters (0.059 to 0.079 inches) wide.

The most interesting part is the labellum. This is a special lip-like petal. It is 13 to 17 millimeters (0.51 to 0.67 inches) long and wide. The labellum is green near its base and turns white, with a dark maroon tip. It has four or five pairs of thin teeth along its sides. These teeth are about 4 to 5 millimeters (0.16 to 0.20 inches) long. In the center of the labellum, there are four rows of small bumps called calli. These calli are packed closely together and are up to 1.5 millimeters (0.059 inches) long.

This orchid usually blooms from November to January.

How It Was Named

The Caladenia dilatata was first officially described in 1810. A famous botanist named Robert Brown gave it its formal name. He found a sample of the orchid near Port Dalrymple, which is close to the mouth of the Tamar River in Tasmania. His description was published in a book called Prodromus Florae Novae Hollandiae.

The second part of its scientific name, dilatata, comes from a Latin word. It means "widened" or "expanded," which might describe a feature of the flower.

There's another similar orchid, the C. tensa, which is an endangered species. It grows in New South Wales, Victoria, and South Australia. For a while, people thought it was the same as C. dilatata.

Where It Lives

The green-comb spider orchid grows in Victoria and Tasmania. You can find it in different places:

• In heathlands near the coast.
• In open forests further away from the coast.

Reproduction and Life Cycle

After the green-comb spider orchid's flower is pollinated, it closes up. It then forms a papery capsule. Inside this capsule, tiny, dust-sized seeds are produced. These seeds can be yellow, brown, or black. When the capsule is ready, it dries out and splits open. Millions of these tiny seeds are then released and carried away by the wind or water.

However, these seeds are very particular! They can only start to grow into a new plant if they get infected by a special type of mycorrhizal fungus. Because of this, only a few of the millions of seeds actually grow into full plants.

How It Interacts with Nature

The green-comb spider orchid has some interesting ways of interacting with other living things.

Attracting Pollinators

The long, thin tips of the orchid's flower produce special scents. These scents act like "attractants" that trick pollinators. The orchid uses a clever method called pseudocopulation. This means the flower looks and smells like a female insect, making male insects think it's a mate. For example, a type of wasp called a Thynnid wasp is often fooled by the flower. The wasp tries to mate with the flower, and in doing so, it helps to pollinate the orchid.

Relationship with Fungi

This orchid has a special partnership with mycorrhizal fungi. This is a mutualistic relationship. The fungus gets some food from the orchid. In return, the orchid absolutely needs the fungus to help its seeds sprout and grow. Without the fungus, the seeds won't germinate. Scientists are still learning exactly how much the orchid depends on this fungus.

Fire and the Orchid

Forest fires can seem scary, but they might actually help the green-comb spider orchid. While scientists don't fully understand how fire affects this orchid, they believe it can be beneficial. Fires help to clear away other plants around the orchid. This means more sunlight can reach the ground, and the temperature at ground level might increase. With fewer plants competing for resources, there might also be more moisture in the soil, which could help the Caladenia dilatata to thrive.

Food Source

The Indigenous name for Caladenia dilatata is koolin. The Coranderrk Aboriginal people have traditionally eaten the tubers (the underground storage roots) of this orchid. They can be eaten either raw or cooked.