It’s typically the elegant, distinguished yet sometimes bizarre flowers that tell us we’re looking at an orchid. But you might say, “other plants are epiphytes, and other plants are native to the tropics and have weird flowers, but what makes an orchid an orchid? What does it take for a plant to be considered an orchid?!
Taxonomists classify or group organisms based on similar characteristics. For plants, the features associated with the flower parts are considered very important when assessing taxonomic relationships. All “orchid” plants belong in the botanical family ‘Orchidaceae’. In very simple terms, plants of the Orchidaceae have flower parts uniquely arranged in a way unlike all other plants:
All orchid flowers have three petals: two lateral petals with the third modified into a “lip“, the part of flower that made orchids famous. Orchid flowers also have three sepals: two lateral sepals and a dorsal sepal opposite the lip. When the flower bud is still closed, what you see are the three closed sepals covering the petals inside.
You might say, well lots of flowers have three sepals covering three petals (e.g. Lilies); how are orchids different?!
OK! What makes orchid flowers distinct from non-orchid flowers is the unique fusion of male and female reproductive parts into a single structure called a “column”. (Once again, there are exceptions…just sayin’) The knob at the end of the column is called the “operculum”, which covers the pollen sacs underneath. Insects transfer pollen to the gooey stigmatic surface hidden on the underside of the column.
The above is an excerpt from my book How Orchids Rebloom. In addition, you will also find detailed photos showing the different flower parts (e.g. petal, lip, column, etc.) in Chapter 3.