Orchids belong to the largest and most diverse group of plants on earth, according to Paul A. Thomas, a horticulturist with the University of Georgia. Beautiful and exotic, these plants are popular with both professional and home gardeners everywhere. With more than 28,000 species and 300,000 cultivars, orchids vary widely in appearance and growth habits. Still, the basic anatomy of an orchid plant remains the same, regardless of the specific species or cultivar.
Like most plants, orchids receive nutrients and water through their roots. Some orchids absorb these through soil, while others attach themselves to a host plant or even a rock and get their nutrients from the humid air of the tropical rain forest. The roots are composed of the main roots and smaller "hair roots" through which the absorption of the minerals and water takes place. Some orchids also have pseudobulbs on the roots, which also absorb and store water for later use.
Orchids have one main stem that rises from the primary root. This stem may be very thick, or rather thin and fragile, depending on the type of orchid. This stem is the main passageway for water and nutrients to travel to all of the other parts of the plant. Small water passageways, often simply called veins, carry water through the stem to the flowers and leaves.
Orchid leaves can vary greatly in size and color. The more light an orchid is exposed to, the darker green leaves will appear. The purpose of the leaves is to photosynthesize, or make food, for the orchid. Once unfurled, the leaves capture sunlight. Very simply, the sunlight combines with the water carried to the leaves through the veins to produce sugar.
The spike rises from the leaves and carries the flower buds. In some orchids, the spike is indistinguishable from the stem. In others, it is entirely separate. The spike may have just one flower perched atop it, or a cluster of flowers. Or, the spike may be lined with buds up and down both sides of it as is the case with Phalaenopsis orchids.
Orchid's flowers are complex and distinctive. While all orchids have the same parts to the flower, the shape and number of these parts will vary depending on the species. The sepals (modified leaves) lie behind the flower and frame it. There are usually three of them. Three petals form the remainder of the flower. The lower petal is called usually called the lip of the orchid and is where insects perch when pollinating the flower. The lip is usually the most colorful part of the flower to attract the insects. The throat is located at the base of the lip and contains the reproductive organs of the flower, including the ovaries and stamen, which is where the pollen is located.