Pterostylis orbiculata facts for kids

The Pterostylis orbiculata, also known as the coastal banded greenhood, is a special plant. It belongs to the orchid family. This plant grows only in the south-west part of Western Australia.

When these plants are not flowering, they often have a circle of leaves close to the ground. This circle of leaves is called a rosette. In years when they do flower, they grow a tall stem with leaves and flowers. Each flowering stem can have up to twenty flowers. These flowers can be reddish-brown, greenish-brown, or green. They also have a unique lip-like part called a labellum. This labellum is usually reddish or brownish and covered with short, stiff hairs.

What it Looks Like

The Pterostylis orbiculata is a terrestrial plant. This means it grows in the ground. It is a perennial herb, so it lives for more than two years. It also loses some parts each year, which is called being deciduous. The plant grows from an underground tuber, which is like a small storage organ.

Plants that are not flowering have a rosette of three to six leaves. These leaves are shaped like an egg. Each leaf is about 8 to 15 millimeters long. They are also about 5 to 10 millimeters wide. These leaves grow on a stalk that is 10 to 20 millimeters long.

When the plant flowers, it has between two and twenty flowers. The flowers can be reddish-brown, greenish-brown, or green. They often have clear white areas. These flowers grow on a stem that is 100 to 250 millimeters tall. This flowering stem has six to twelve leaves on it. These stem leaves are shaped like a lance or an egg. They are about 35 to 45 millimeters long and 4 to 9 millimeters wide.

The flowers themselves are about 15 to 18 millimeters long. They are also about 6 to 9 millimeters wide. The top part of the flower, called the dorsal sepal, and the petals form a hood. This hood covers the central part of the flower. The dorsal sepal is 14 to 18 millimeters long and feels smooth. The petals are 9 to 11 millimeters long and about 4 millimeters wide.

The two side sepals, called lateral sepals, point downwards. They are joined together for most of their length. This forms a shape that is almost perfectly circular. This circular part is about 12 to 14 millimeters long and wide. The labellum is oblong, which means it's longer than it is wide. It is about 4 to 5 millimeters long and 3 millimeters wide. The labellum is reddish or brownish. It is also covered with short, stiff hairs. These plants usually flower from June to early August.

How it Got its Name

The coastal banded greenhood was first officially described in 2017. Two botanists, David Jones and Christopher French, gave it its first formal name. They called it Urochilus orbiculatus. This description was published in a magazine called Australian Orchid Review. The plant they studied was found near Mogumber.

In 2018, the same two authors changed the name. They renamed it Pterostylis orbiculata. They did this to fit different ways of classifying orchids. Before these official names, people knew it as Pterostylis sp. 'coastal'. The second part of its scientific name, orbiculata, comes from a Latin word. It means "circular." This name refers to the almost circular shape made by the joined side sepals of the flower.

Where it Lives

Pterostylis orbiculata grows in Western Australia. You can find it from north of Geraldton down to Bunbury. There are also a few groups of these plants further inland. It likes to grow in areas with shrubs, woodlands, and forests. Sometimes, you can even find it growing around large rock formations called granite outcrops.