The roots of orchids are unique in the plant kingdom. They are thick and mostly white, but are not produced with the same abundance as in other plants.

The chain may divide when two or more growths develop from the last pseudobulb in one year. This is how large clumps can form over several years. It is difficult to make comparisons with other structures and plants. A pseudobulb is unlike a daffodil or an onion bulb, which consists of a layer of sheafs, or false leaf bases, one on top of the other. It is also unlike a potato, which is a starchy, tuberous structure.

While the vandas can become considerably tall, and at some stage in their life need to be reduced in height, the phalaenopsis are selfregulating, never attaining much upward growth, because the older leaves are shed at the same rate as new ones appear. The leaves of vandas and other monopodial orchids are semi-rigid, while those of phalaenopsis are broad and flat. In the wild, the latter plants are not subjected to extreme temperatures or bright sunlight, and their wide surface is designed to catch as much of the filtered light as possible.

Pseudobulbs are the longest-living part of the plant and will exist in a dormant state long after the leaves have been shed. Leafless pseudobulbs are known as back bulbs. In evergreen types, such as cymbidiums, a healthy plant consists of more pseudobulbs in leaf than out of leaf. With the deciduous types, such as lycastes, a cluster of leafless pseudobulbs with only the leading one in leaf is normal.

In the same way as the leaves are shed from the plant after one or a few years, so the roots die naturally to be replaced by those from the new growth. In monopodial orchids such as vandas, the roots are made at intervals

Dendrobiums produce some of the longest pseudobulbs among cultivated orchids, and these become so elongated in some species that they are called “canes”. In this genus, they we mostly leafed along their entire length, as in Dendrobium pierardii. Many dendrobiums are deciduous and so remain in a leafless, dormant state for much of the year. Perhaps the longest pseudobulbs of all belong to the species Gramtnatophyllum speciosum. This giant orchid is known as the sugar cane orchid, a reference to its leafy canes that can reach a length of 5m (16ft), becoming pendent under their own weight. Between these ea-tremes are numerous orchids that grow to a, height of 1.2m (4ft), and as many again that are below 30cm (12in).

The purpose of this is not fully understood, but it may be that they are a protection from insects or a means of preventing water lying on the foliage, which could be detrimental on cold nights. Other monopodials, including vandas, have leaf tips that are serrated; these enable the plant to dispose of any excess moisture taken up through the roots.

The glow of light at the end of this hollow pseudobulb indicates the small hole at the bottom of the structure. In the wild, these orchids are infested with huge colonies of ants which live inside the hollow pseudobulb. The ant has a comfortable home, and the plant remains untroubled by parasites.