Typically called spider orchids, the 50 species of plants in the genus Brassia belong to the orchidaceae, or orchid, family. These plants are native to wet forest habitats in parts of Central America and regions of South America. Their spider-like look attracts a parasitic, spider-killing wasp that usually lays its eggs on spiders. Confused by the plant's spidery appearance, the wasp lays its eggs on the flowers, thereby transferring pollen from flower to flower and pollinating the plant. Many varieties of the orchids are popular with gardeners.
Brassia plants are epiphytic, meaning that they live on a host plant but do not feed on the host; they derive their nourishment from the air. The epiphytic plant usually clings to the host plant with aerial roots. Another characteristic of a Brassia plant is its pseudobulb, or false bulb. In spider orchids, the pseudobulb is a large stem that rises from the rhizome, which is a root-like stem that produces stems and roots. They generally range in color from yellow-green to mid-green and can be cylindrical, spherical, or ovoid.
The leaves and flower stem arise from the pseudobulb. Depending on the species and the variety, Brassia orchids usually have two to three long narrow, leathery leaves. These leaves often range between 7 to 16 inches (about 18 to 40 cm) long, but the size varies with the variety and species. Typically, they are up to 2.5 inches (about 6 cm) wide and solid in color.
When the plant blooms, a long slightly arched stem rises from the pseudobulb and bears flowers from the top of the stem. These stems usually range from 16 inches (about 40 cm) to more than 18 inches (about 46 cm) long and might bear 12 fragrant flowers. When the rhizome has several nodes, each producing leaves and flowers, the plant can resemble an exotic bouquet. Growers often separate the rhizomes in order to produce singular, simple plant specimens.
The shapes of the petals and sepals, or segments of the calyx, create the exotic shape of the flowers of the Brassia orchids. They are so long and narrow that they resemble spider legs; when massed together, they look like a spider web. On most Brassia plants, a short tongue-like lip hangs down between the lower sepals, looking like the imaginary spider's body. Sometimes the flowers are so closely spaced on the stem that they resemble a giant, spiked caterpillar crawling out of the leaves.
The color of the Brassia flowers ranges from species to species and differs within the cultivars of the different species. The B. caudata has light green sepals and petals that are spotted and barred with brown, especially near the base. The triangular lip is light yellow with reddish brown spots. B. lawrenceana has green or yellow flowers with red-purple spots and a white, diamond-shaped lip with very few purplish spots at the base.
The B. verrucosa's arching stem may grow from 12 to 30 inches (about 30 to 75 cm) long, sprouting from a medium green pseudobulb that averages 3 inches (about 7 cm) long by 2.5 inches (about 6 cm) wide. The flowers are yellow to green, marked with reddish brown spots, and may measure from 4 inches (about 10 cm) wide and 5 or 6 inches (about 12 to 15 cm) long. Some cultivars have flowers that measure up to 10 inches (25 cm) long. The tongue-like lip often is white and spotted with dark green or brown, wart-like spots. In the wild, it typically grows in southern Mexico and Venezuela, but growers throughout the world possess it as a houseplant.