Pterostylis rubiginosa facts for kids

Pterostylis rubiginosa is a special type of orchid that only grows in northeastern New South Wales, Australia. It's often called a "greenhood" because of the shape of its flowers. When this plant is not flowering, it has a small group of leaves shaped like a circle, called a rosette. But by the time the flowers bloom, these leaves have usually dried up. The flowering plants can have up to seven white flowers with cool rusty brown stripes, growing on a thin, strong stem.

What Does This Orchid Look Like?

Pterostylis rubiginosa is a plant that grows from the ground, not on trees. It's a perennial plant, meaning it lives for more than two years. It's also deciduous, which means its leaves fall off at certain times of the year. This plant is a herb with an underground tuber (a swollen part of the stem, like a small potato).

When the plant is not flowering, it has a rosette of two to seven egg-shaped leaves. These leaves spread out and are about 5 to 10 mm (0.2 to 0.4 in) long and 4 to 8 mm (0.16 to 0.31 in) wide. When the plant is ready to flower, new leaves might grow on a side shoot, but the older leaves usually dry up before the flowers open.

The Flowers

This orchid can have up to seven flowers spaced out along a thin, wiry stem. The stem grows to be about 100 to 250 mm (4 to 10 in) tall. Usually, only about three flowers are open at the same time. The flowers are white with rusty brown stripes. They are about 8 to 9 mm (0.31 to 0.35 in) long and about 3 mm (0.12 in) wide.

The top sepal (part of the flower that protects the bud) and the petals are joined together. They form a hood-like shape over the column (the central part of the orchid flower). This hood is called a "galea." The top sepal is shaped like a spear or an egg, about 11 to 13 mm (0.43 to 0.51 in) long and 4 to 6 mm (0.16 to 0.24 in) wide. It curves forward and has a short point.

The side sepals stand upright and are held close to the galea. They are joined together for most of their length, leaving a small opening about 2 mm (0.08 in) wide. The tips of these side sepals curve forward and are about 2 mm (0.08 in) long, but they don't reach the very top of the galea. The labellum (a special petal in orchids) is not visible above the gap (called the sinus) between the side sepals. People have seen this orchid flowering between mid-November and early December.

How This Orchid Got Its Name

This greenhood orchid was first officially described in 2016. Two botanists, David Jones and Lachlan Copeland, gave it the name Speculantha rubiginosa. They published their description in a magazine called Australian Orchid Review, based on a plant they found in the Dorrigo National Park.

Later that same year, the same botanists changed the name to Pterostylis rubiginosa. They did this to fit different ways that scientists group similar plants together. The second part of the name, rubiginosa, comes from a Latin word that means "rusty." This name was chosen because of the rusty brown stripes on the orchid's flowers.

This orchid is similar to a few other types that haven't been officially named yet. These include P. recta, found near Wauchope, and P. oresbia, found in the Barrington Tops and Werrikimbe National Parks.

Where Does This Orchid Grow?

This greenhood orchid grows in open forests and nearby grassy areas. It is found in a small part of the Dorrigo National Park in New South Wales.