Swamp mignonette orchid facts for kids

The Microtis atrata, often called the swamp mignonette orchid or yellow onion orchid, is a special type of orchid. It is found only in southern Australia, meaning it is endemic there. This small plant has a single thin leaf and many yellowish-green flowers.

These flowers are the tiniest of all Australian orchids that grow on the ground. Swamp mignonette orchids often grow in huge groups after a bushfire. Even though they are small, their large numbers make them easy to spot against the blackened ground. Sometimes, this orchid is also known as Microtidium atratum.

What Does the Swamp Mignonette Orchid Look Like?

The swamp mignonette orchid is a herb that grows in the ground. It is a perennial plant, meaning it lives for more than two years. It is also deciduous, so it sheds its leaves at certain times. This orchid has an underground tuber, which is like a small storage root.

From this tuber grows a single, smooth leaf. This leaf stands straight up and is usually about 3 to 9 centimeters (1.2 to 3.5 inches) long. It is about 3 millimeters (0.1 inches) wide.

Tiny Flowers and Their Features

The orchid's flowering stem can be 1 to 4 centimeters (0.4 to 1.6 inches) long. It holds between two and forty or more yellowish-green flowers packed closely together. The whole plant can grow to be 5 to 12 centimeters (2 to 4.7 inches) tall. If it grows in water, it can even reach up to 20 centimeters (7.9 inches) tall.

Each flower is very small, about 2 millimeters (0.08 inches) long and wide. This makes them the smallest ground-dwelling orchids in Australia. As the flowers get older, they turn black. The top part of the flower, called the dorsal sepal, is shaped like an egg. It is about 1 millimeter (0.04 inches) long and wide and covers the central part of the flower, called the column.

The side sepals are longer and spread out. The petals are egg-shaped and curved inwards. The special lip of the flower, called the labellum, is also oblong or egg-shaped. These orchids usually bloom from September to December. Their flowering is often triggered by a bushfire that happened the summer before.

Where Do Swamp Mignonette Orchids Grow?

The swamp mignonette orchid can be found in several parts of Australia. It grows in the south-west of Western Australia. You can also find it in the south-east of South Australia, in southern Victoria, and in northern Tasmania.

These orchids prefer wet places. They often grow in swamps or in areas that get very wet during winter. Sometimes, they even grow in standing water. After a summer fire, they can form huge groups of plants in these wet areas.

Protecting the Swamp Mignonette Orchid

The Western Australian Government's Department of Parks and Wildlife says that Microtis atrata is "not threatened" in Western Australia. However, in South Australia, it is considered "endangered," meaning it is at high risk of disappearing. In Tasmania, it is listed as "rare." This means it is important to protect these special orchids in different parts of Australia.