Ansellia

Ansellia is considered a monotypic genus of detrivorous orchid, with only one species, Ansellia africana, commonly known as African Ansellia or Leopard Orchid, however, it is in fact a complex group of species which share common floral structure and growth habit.
The plants are found throughout neotropical and subtropical Africa. It was named after John Ansell, an English assistant botanist. who found the first specimens in 1841 on the Fernando Po Island in West Africa. This genus is abbreviated as Aslla in horticultural trade.
It is referred to along with Grammatophyllum as a "trash basket" orchid due to its odd habit of creating a makeshift container of aerial roots to catch and digest falling leaf litter for nutrients. Not exclusively confined to orchids, there are many neotropical detrivorous species which have developed the ability to collect and digest leaf litter, such as Platycerium and Nepenthes ampullaria, with ferns and bromeliads observed as being more efficient decomposers than orchids or other epiphytic species.^[1]

Distribution and habitat

This orchid is native to tropical and southern Africa,^[2] found alongside coasts and rivers in the canopy of trees, usually at elevations lower than 700 m (occasionally up to 2,200 m).^[1]

Description

This is a large, perennial, detritivore, and epiphyte, or at times a terrestrial plant, growing in sometimes spectacular clumps, attached to the branches of tall trees. The white, needle-like, aerial roots are characteristic for this orchid. They point upwards, taking the form of a trash basket around the tall, many-noded, fusiform, canelike, yellow pseudobulbs, catching the decaying leaves and detritus upon which the plant feeds. These pseudobulbs can develop a gigantic size, up to 60 cm long. This robust orchid can grow very large, sometimes with an estimated weight over a tonne. Even eagle owls (Bubo bubo) have been seen to make their nest in such a clump.
The roots which penetrate the substrate can become very thick and cord-like to support the weight of the plants, and are typically very different in form than the roots which comprise the trash basket as the aerial roots are non-absorbing. Breakdown and absorption of nutrients by the plant from the trash basket is performed by its fungal symbiots and the active absorbing roots.^[1]
These pseudobulbs carry on their top 6 to 7, narrowly ligulate-lanceolate, acute, plicate, leathery leaves. They give rise to a paniculate inflorescence, up to 85 cm long, with many (10 to 100), delicately scented flowers, 6 cm across.
The three-lobed lip grows into three yellow projections. The tepals are yellow or greenish yellow, lightly or heavily marked with brown spots. The flowers are short-lived, seldom lasting longer than 10 days, but are produced in abundance provided the plants have received high light levels throughout the year.

Cultivation

An easy species to grow, in cultivation the plants usually bloom with a terminal inflorescence from the older pseudobulbs, some plants however, will produce flowers from newer pseudobulbs in odd years. These plants are shy to flower in cultivation unless they receive very bright light of around 2000 foot candles and given a dry rest for about 6 weeks in the fall. In habitat, the plants can go periods of several months without water, and are very drought tolerant, but the plants tend to perform better if kept evenly moist throughout the year. Plants which are receiving enough light will take on a yellowish coloration in the leaves. This is normal as these plants use CAM photosynthesis. Plants with very green leaves are not receiving enough light.
The plants are detritivores and fungal magnets in habitat and in cultivation and tend to culture mychorhizzial fungi they pick up from their environment since this species is a trash basket orchid that in nature creates a network of interlocked airborne roots to collect leaf litter and digest it, they have a tendency to rapidly break down their growing medium more so than other species of orchids. Addition of 50% dried spagnum moss and 50% bark keeps the medium from souring with this species. It is common for the growing medium of these plants to have a very strong mushroom-like odor, and this is normal for these plants. Unlike most epiphytic orchids, the roots of this species are not appreciably photosynthetic, are white and pale, and resemble the roots of terrestrial and saprophytic orchids.^[1]
When the plants are not getting enough nitrogen, they will start growing a trash basket with numerous non-absorbing roots growing upwards. These plants do not produce a trash basket if they are receiving sufficient nitrogen regularly. They are very heavy feeders in cultivation and require regular fertilization and have high nitrogen requirements. These plants can be difficult to repot without damaging the plants root mass and they have a tendency to grow very rapidly. These plants can and will crack their pot open as the roots fill and their roots tend to not be deciduous and remain alive on older pseudobulbs and these clinging roots usually have to be cut away from the walls of the pot during repotting.
These plants in habitat usually bloom at the end of dry spells, however, this species has a unique habit of blooming at any time of the year and several times a year if the plants have been grown in high light levels and are subjected to short dry spells of 4–6 weeks every 6 months. There is wide variability of flower shape, color, and markings, and this species is widespread across Africa. Although it is considered as a single species due to floral structure and plant habit, it is in fact a complex group of species which can all hybridize with each other and the plants grow through most of neotropical and subtropical Africa. This group like Encyclia, Bulbophyllum, and Epidendrum is in a state of active speciation.
The plants can take light frost but drop their leaves, and should not be exposed to freezing temperatures. These plants are also somewhat heat sensitive and have a lower thermal death limit than many orchids, and temperatures above 120 degrees F will severely damage them and kill the tops of the pseudobulbs if the plants do not have sufficient air movement and are subjected to intense heat. They prefer moderate temperatures. The species is tolerant of low humidity and can be grown as a houseplant quite successfully provided they receive high light levels. The plants tend to form crisscrossed, impenetrable mats of aerial roots completely covering the top of the bark substrate. They can be large, very attractive, stately plants provided their trash basket of aerial roots is kept trimmed down to bark level and they are in a very large, shallow clay pot. They are low maintenance plants in cultivation, and like to be kept lightly moist all the time, but not wet.
Ansellia africana