Tree spider orchid facts for kids

Quick facts for kids Tree spider orchid
Dendrobium tetragonum var. tetragonum
Scientific classification
Genus:	Dendrobium
Species:	tetragonum
Synonyms
Synonyms Callista tetragona (A.Cunn. ex Lindl.) Kuntze * Dendrocoryne tetragonum (A.Cunn. ex Lindl.) Brieger * Tropilis tetragona (A.Cunn. ex Lindl.) Butzin * Tetrabaculum tetragonum (A.Cunn. ex Lindl.) M.A.Clem. & D.L.Jones * Dendrobium tetragonum var. tomentosum Nicholls * Dendrobium tetragonum var. variabile P.A.Gilbert

The tree spider orchid, also known as Dendrobium tetragonum, is a special type of orchid. It grows on other plants, like trees (this is called being an epiphyte). Sometimes, it can even grow on rocks (this is called being a lithophyte). This unique orchid is found only in eastern Australia.

Tree spider orchids have unusual stems called pseudobulbs. These stems hang down and are thin at the bottom. Then, they get wider and have four sides before getting thin again at the top. Each pseudobulb has a few thin, tough leaves at its end. The plant produces up to five flowers on short stems. Because this orchid can look quite different from one place to another, there are five main types, called subspecies, and one variety. Some of these even have their own special names!

Dendrobium tetragonum var. cacatua (yellow tree spider orchid)

What Does the Tree Spider Orchid Look Like?

The tree spider orchid is a herb that hangs down. Its pseudobulbs are usually between 150 and 600 mm long. They are about 6 to 9 mm wide. The base of the pseudobulb is thin and wire-like. But the upper part is thick and has four sides. Each pseudobulb ends with a pointed tip. It has two to five leaves that are thin but feel like leather. These leaves are about 50 to 90 mm long and 15 to 40 mm wide.

Flowers and Their Colors

The flowering stems are short, only 10 to 35 mm long. Each stem can have up to eight flowers. The flowers can be very different in size and color. This depends on which type of tree spider orchid it is. Flowers can be from 30 to 120 mm long and 20 to 80 mm wide. Their colors range from green to light yellow. Some flowers might have red spots. The special lip-like part of the flower, called the labellum, can be white or yellowish. It often has red, brown, or purple marks.

The outer parts of the flower, called sepals, are 20 to 70 mm long. They are 2 to 5 mm wide. The inner parts, called petals, are 10 to 40 mm long. They are 1 to 2 mm wide. The labellum is 8 to 15 mm long and 6 to 20 mm wide. Tree spider orchids usually bloom between April and November.

How Was the Tree Spider Orchid Named?

The Dendrobium tetragonum was first officially described in 1839. A botanist named Allan Cunningham found a sample of the plant. He found it "hanging loosely from the stems of small trees" near Moreton Bay. The description was then published in a science magazine called Edwards's Botanical Register. This magazine was put together by John Lindley.

Different Types of Tree Spider Orchids

Since the tree spider orchid can look so different, scientists have divided it into several types:

• Dendrobium tetragonum var. cacatua is known as the yellow tree spider orchid. Its flowers are green to light yellow. They have a few thin reddish-purple marks. The labellum is white, usually without any marks. It flowers from July to September.
• Dendrobium tetragonum subsp. cataractarum has yellowish-green flowers. These flowers have red, purple, or brown marks on the edges of their sepals. The labellum is a pale, creamy color with reddish-purple marks. It flowers from August to September.
• Dendrobium tetragonum subsp. giganteum is called the blotched tree spider orchid. It has greenish-yellow flowers with big red blotches. Its labellum is white with red and purple lines. It flowers from April to November.
• Dendrobium tetragonum subsp. melaleucaphilum is the flared tree spider orchid. It has the largest flowers of all the types. The flowers are green to greenish-yellow with reddish blotches. The labellum is white or pale yellow with red or purple marks. It flowers from May to October.
• Dendrobium tetragonum subsp. serpentis has flowers that start green and then turn yellow. They have few or no marks, except on the labellum. The labellum is white to pale cream with reddish-purple marks. It flowers from August to September.
• Dendrobium tetragonum subsp. tetragonum is the banded tree spider orchid. It has the smallest flowers. These flowers are green to greenish-yellow with dark reddish-brown bands on their edges. The labellum is cream-colored or yellow with brown, red, or purple marks. It flowers from May to October.

Where Do Tree Spider Orchids Live?

Tree spider orchids usually grow on trees in rainforests. They also like shady spots next to streams. Sometimes, they grow on paperbark trees, especially a type called Melaleuca styphelioides. You might even find them growing on rocks. Different types of this orchid live in different areas. These areas are along the coast or near the coast in New South Wales and Queensland.

• Dendrobium tetragonum var. cacatua is found from the Mount Windsor Tableland near Cape Tribulation. It stretches down to the Eungella National Park in Queensland.
• Subspecies cataractarum only lives in the Connors Range. This is west of the Cape Palmerston National Park in central eastern Queensland.
• Dendrobium tetragonum subsp. giganteum grows between the Iron Range and Mackay in Queensland.
• Dendrobium tetragonum subsp. melaleucaphilum is found from the Blackdown Tableland National Park in Queensland. It goes all the way to the Blue Mountains in New South Wales.
• Dendrobium tetragonum subsp. serpentis is only found in the northern parts of the Blackdown Tableland.
• Dendrobium tetragonum subsp. tetragonum ranges from Fraser Island in Queensland. It goes down to Tomerong in New South Wales.