Arachnis, also known as Arachmanthe, is a genus of plants belonging to the Orichidaceae family that is native to a variety of locations throughout Southeastern Asia. There are 20 recognized species in the Arachnis genus, some of which are too large to be cultivated in a greenhouse. The Arachnis genus is named after its oddly shaped flowers that suggest the shape of a spider.
A healthy Arachnis orchid blossoms twice a year in the late spring and late fall. The blossoms of the Arachnis orchid have have spindly, brightly-colored petals that resemble the appendages of a spider. Most of these orchid flowers are colored with alternating shades of yellow and brown. These long-lasting flowers have a strong odor, and some species are cultivated for the cut flower market.
All of these types of orchids grow as either epiphytes or lithophytes. This means that they do not need soil to survive. Instead, they obtain their nutrients from the air, the tissue of other plants, or rain water. In its native environment, these orchids grow above the forest floor in lowland rainforests.
Members of the Arachnis genus have thick stems that sprawl along rainforest canopies to cover multiple trees. These fast-growing orchids are usually propagated by root cutting, but smaller species can be divided. Arachnis orchids produce foliage in the form of fleshy leaves that typically last throughout the year.
While Arachnis orchids are rarely available at the retail level, an experienced orchid enthusiast can successfully cultivate the smaller species under proper conditions. These plants require a considerable amount of heat and humidity and should be exposed to as much direct, bright sunlight as possible. When a new plant is being cultivated, it should be allowed to hang freely or on cork until it begins to become established. The plant can be then be introduced to an appropriate substrate like bark cuttings or tree fern.
The two best known species in this genus of orchids are A. flos-aeris and A. ahookeriana. A. flos-aeris is a native to Malaysia and has a thick stem that climbs up the sides of large trees in its natural habitat. The flowers of the orchid are yellow-green with purple lines. A. hookerania is a much smaller species that is an important plant in the commercial cut flower industry. This species has become rare in the wild, but horticulturalists have developed hybrids that are easier to cultivate.