WHAT IS AN ORCHID?
Despite their exotic sounding name, orchids occur in almost every range of habitat apart from deserts and glaciers. The great majority are found in the tropics, although there are a few species that can be found above the Arctic Circle. They are also one of the largest plant families on the planet consisting of over 25,000 species – second only to the aster family ‘Asteraceae’.
Although its name may sound exotic, the word orchid comes from the Greek word Orchis – meaning testicles! This unfortunate label arrived because it described the two rounded tubers that were commonly found on many of the native European orchid species.
As you can imagine orchids come in many different shapes and colours. The characteristics that they all have in common however is that the male and female parts of the flowers (the stamens and pistol) are fused together to form the column.
Other characteristic include the arrangements of the flower. There are three similar petals and three petals. The third petal - known as the lip or labellum – is different to the other two and usually the most eye- catching. The lip has evolved to attract the pollinators which – depending on the species – can include ants, bees, wasps, gnats, butterflies, moths and even birds!
All orchids are classed as perennial herbs and lack any permanent woody structure. They can grow according to two patterns:
Monopodial: The growing stem is formed from a single bud, with the leaves being produced at the apex of the apex. As more leaves are produced, the stem grows longer accordingly. The stem of orchids with a monopodial growth can reach several metres in length, as demonstrated by examples in the Vanda and Vanilla species.
Sympodial: The plant produces a series of adjacent shoots which grow to a certain size. Once in bloom the shoot will stop growing, however the orchid will continue to grow in size by producing a new shoot. Sympodial orchids grow will laterally rather than vertically - following the surface of their support. The growth continues by the development of new ‘leaders’s which have with their own leaves and roots. These will be found sprouting from - or next to - those of the previous year, as noted in Cattleya species. While a new lead is developing, the rhizome may start its growth again from a so-called 'eye' - an undeveloped bud found at or near the base of the plant.
Although many orchid flowers are indeed spectacular, most varieties produce seeds are in fact tiny – approximately 0.5mm in diameter, although some species can produce seed as big as 5mm!
While the seed produced is generally small, orchid plants make up for this in sheer quantity of seed produced- so much is produced that it can look like thousands of dust particles floating on the air!
Strangely for such a successful plant, the seeds of many orchid varieties cannot germinate or grow on their own. Research has shown that these seeds have a symbiotic (mutually beneficial) relationship with specialist fungi so that they can receive the nutrients required to germinate. This is because the seed lacks an endosperm - the tissue found in other seeds which provides nutrition in the form of starch.
Advances in horticultural production techniques have now advanced to such a point that they are able to germinate far more seeds than would otherwise happen in the orchid’s native habitat. This is why orchids are now commonly available in supermarkets and retail plant centres.