Riverina rustyhood facts for kids

The Pterostylis petrosa, also known as the Riverina rustyhood, is a type of orchid plant. It is found only in New South Wales, Australia. This special plant has a group of leaves at its base. It can grow up to eight dark brown flowers. These flowers have clear "windows" and long, spreading tips. They also have a thin, brown part that looks like an insect.

What Does the Riverina Rustyhood Look Like?

The Riverina rustyhood is a plant that grows from an underground tuber (like a small potato). It is a perennial plant, meaning it lives for more than two years. It is also a deciduous plant, which means its leaves fall off at certain times of the year.

At the bottom of its flowering stem, it has a group of six to ten egg-shaped leaves. Each leaf is about 15 to 25 mm (0.6 to 1 inch) long and 6 to 9 mm (0.2 to 0.4 inches) wide. Often, these leaves have dried up by the time the plant flowers.

The plant grows a flowering stem that is about 90 to 150 mm (3.5 to 5.9 inches) tall. On this stem, it can have up to eight dark brown flowers. Each flower is about 30 to 38 mm (1.2 to 1.5 inches) long and 10 to 12 mm (0.4 to 0.5 inches) wide. Each flower sits on a thin stalk that is 14 to 20 mm (0.6 to 0.8 inches) long.

The top part of the flower, called the "galea," forms a hood over the center. This hood is made from the top sepal and petals joined together. The top sepal has a thin, thread-like tip that is 8 to 10 mm (0.3 to 0.4 inches) long. The side sepals point downwards and are wider than the hood. They are slightly curved, have tiny hairs on their edges, and end in a thin, thread-like tip that is 14 to 20 mm (0.6 to 0.8 inches) long.

The "labellum" is a special part of the flower that looks like a brown insect. It is 7 to 9 mm (0.3 to 0.4 inches) long and about 3 mm (0.1 inches) wide. It has two long hairs at one end (like a head) and 9 to 12 shorter hairs along each side (like a body). These orchids usually flower from September to November.

How Did It Get Its Name?

The Riverina rustyhood was first officially described in 1983. Two botanists, David Jones and Mark Clements, wrote about it after finding a sample near The Rock. They published their description in a science journal called Muelleria.

The scientific name petrosa comes from a Latin word meaning "rocky" or "stony." This name was chosen because the orchid grows in rocky places. It also refers to the exact spot where the first sample was found.

Where Does It Live?

The Riverina rustyhood lives in the Riverina area of New South Wales. It grows on a few stony hills, often found in cracks in rocks and on rocky ledges.