Orchids can be quite flamboyant, sensual or downright sexy — some more so than others. The name orchid literally means testicle in Greek (ὄρχις/órkhis), a rather suggestive but suitable name it would seem. Linnaeus categorized the family as Orchidaceae, but the common name “orchid” came about later when John Lindley (incorrectly) aimed to extract the Latin stem (orchis) from Orchidaceae in 1845.
History & taxonomy
There are over 25,000 species of orchids in the world, some say as many as 30,000 and several hundred new species are discovered each year. There is evidence of orchids dating back as far as the age of the dinosaurs, 120 million years ago, making them not only the second largest but also the oldest flowering plant family in the world. Orchids are found on every continent except Antarctica (but is found on Macquarie Island, very close to Antarctica) and grow pretty much everywhere except for in the driest deserts and on glaciers. A majority of orchids are found in the tropics, mostly in Asia and South- and Central America. On top of this staggering number of natural species there are about 120,000 registered manmade hybrids, and more are registered all the time. Orchids are primarily grown for their beautiful flowers, with one exception. The seed pods from the Vanilla orchid (yes, vanilla is an orchid) are harvested as a spice, and vanilla is the second most expensive spice in the world after saffron.
The taxonomy changes all the time as science evolves, but the family Orchidaceae is currently placed in the order Asparagales with five recognised subfamilies. They are: Apostasioideae (2 genera, 16 species) from south-western Asia, Cypripedioideae (5 genera, 130 species) from the temperate regions as well as tropical America and tropical Asia, Vanilloideae (15 genera, 180 species) from humid tropical and subtropical regions as well as eastern North America, Epidendroideae (500+ genera, 20,000+ species) cosmopolitan*, Orchidoideae (208 genera, 3,630 species) also cosmopolitan*. (*Found more or less all over the world.)
Many orchids have a unique relationship with a single type of bird or insect that can pollinate their flowers. Charles Darwin reasoned that the orchid family was exceptionally adept at the mechanism of natural selection. For example, he argued that pollinator for the Angraecum sesquipedale orchid must have a tongue or proboscis long enough to reach from the mouth of the 30 centimeter long spur to the apex where the nectar was held. Scientists of the day laughed at this ridiculous notion, but a sphinx moth (Xanthopan morgani praedicta) equipped with a tongue of the appropriate length was actually discovered on Madagascar in 1903. Many of Darwin’s observations regarding orchid pollination can withstand critical scrutiny even today – almost a century and a half later.
How orchids grow
There are five basic types of orchids based on their growing conditions: Aquatics (grow in water), Epiphytes (grow on branches/mossy trees but are not parasitic), Lithophytes (grow among rocks/on stones), Saprophytes (grow in leaf litter) and Terrestrial (grow in sand/clay/soil). Most orchids are perennial epiphytes however and grow attached to trees or shrubs in the tropics and subtropics. The placement provides nice filtered sunlight, even moisture during the rainy periods, and constant air circulation.
Orchids has two growth patterns, monopodial and sympodial. Monopodial orchids grow one stem from a single bud. Leaves grow from the apex and the stem and grow longer accordingly. Once the monopodial orchid flowers from the centre top leaves, it has reached its maturity and will not grow any more. Sympodial orchids grow laterally rather than vertically, producing a series of adjacent shoots. The mature shoot will bloom and then stop growing and is later replaced. The growth continues by development of new leads along the rhizome, a creeping rootstock that is usually found underground.
Many orchids have pseudobulbs that can store water and nutrients for drier periods. Some species have big fat bulbs, others are narrow and tall. The whole base of the stem of sympodial epiphytes actually serves as a pseudobulb. Older pseudobulbs often shed their leaves and become dormant, called backbulbs. Other active pseudobulbs exploit the last reserves accumulated in these backbulbs until they eventually die off. In warm and humid climates, pseudobulbs are not necessary. Epiphytic orchids have modified aerial roots surrounded by a spongy epidermis called a velamen. The velamen is really good at absorbing humidity in the air. When the velamen fill with water it changes color from silver to a healthy green. The same thing happen when we water.
Orchids are distinguished from other plants by some very evident apomorphies, such as they are bilaterally symmetric (zygomorphic), many resupinate, one petal (labellum) is always highly modified, stamens and carpels are fused, and the seeds are extremely small.