What is an Orchid?
Orchids are monocots which evolved 40 - 80 million years ago from a lily-like relative. As a group, the orchid family is a young, rapidly evolving family. Many species have complex pollination mechanisms, such as pollinator-specific structures; these include parts for insect mimicry, pollinator traps, and/or nectar rewards. These mechanisms suggest co-dependent relationships between plant and pollinator. 

Orchids occur on the ground (terrestrials), on rocks (lithophytes) and on trees (epiphytes). Epiphytes do not damage or derive any nutrients from their tree hosts. All of Indiana's 43 species of orchids are terrestrial.

 Unique Orchid Characteristics
One of the most striking features of the orchid flower is one (often) showy, large petal, called the lip or labellum (Fig 1). Another key character of the orchid family is known as the column (Fig. 2). The column is a fusion of reproductive parts (anthers, filaments, stigmas and styles) that are normally separate in other plants. Orchids, like all monocots, have their parts in three and veins parallel. Pollen is not dusty, but massed together in hard or waxy structures called pollinia. They ovary is located below the petals. Seed capsules produce 1,000 to over 1,000,000 tiny dust-like seeds (Fig. 3), which have no endosperm (stored food). In the wild, nutrition is provided by mycorrhiza(e), which is a symbiotic relationship between plant and fungus. The mycorrhizal hyphae invade the developing orchid embryo, and provide sugars and  carbohydrates necessary for the orchid seed to grow. Without the mycorrhizae, orchid seeds cannot germinate in the wild.

Figure 1. Large showy labellum	Figure 2. Column	Figure 3. Seed capsule x 35

 Illustrations Copyright 1994 CMVLeBlanc; used by permission.
 

Orchid Diversity
Orchids exhibit an incredible range of variability in shape, color, size and fragrance. Even orchid leaves, notably less showy than the flowers, vary; thick and leathery or thin and flexible, folded at the midvein, or pleated, round in cross-section, or flattened laterally.

Orchid flowers can be as small as the head of a pin (Platystele sp. Central America) or greater that 10" (Grammatophyllum  sp., New Guinea). The vine Vanilla planifolia  of tropical America is the source of vanilla extract. Fragrances vary from citrus-like (Polystachys pubescens ), to fetid (Satyrium pumilum, a fly-pollinated species from South Africa). And perhaps the most unusual is the Australian species Rhizanthella gardneri, which lives and flowers completely below the earth's surface!

The diversity of this group of plants is truly amazing. In addition, over 60,000 hybrid orchid exist, created from over 150 species, and more are being created every day!

Orchid Pollinators
Although orchid pollinators tend to be insects (86%), birds and bats visit orchid flowers as well. Bees and wasps are the most common orchid visitors, tending to pollinate yellow and green flowers which often provide nectar for the pollinator, and visual color or "nectar guides" to direct the bees to the column. Flies pollinate brown, maroon and full green flowers that often are (sometimes unpleasantly) fragrant (fruity, fetid, or of carrion) but have no nectar. Butterflies pollinate pleasantly fragrant flowers that are yellow, orange, red and bluish. These flowers often have nectar guides and spurs (equal in length to the long tongues of the butterflies) filled with nectar! Moths visit night-fragrant white flowers. Some orchid flowers never fully open (cleistogamous), and are self-pollinated.

Some orchid flowers mimic their pollinator: Trichoceros species (fly mimics) and Ophyrs  species (bee mimics) look and smell like a female of the species and thus the male species attempts to mate with the flower, and in doing so, pollinates it. Orchid flowers can trap their pollinator (Paphiopedilum species), with exit only possible by brushing against the pollinia. Another trap species (Coryanthes speciosa) has bucket traps where the only exit from a pool of liquid is first past the stigma, then the pollinia. Still other orchids (Cycnoches species) have spring loaded pollinia, that are projected onto the back of the visiting bee.