What Makes an Orchid an Orchid?

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A question we often get asked is: What makes an orchid an orchid...or, how are orchids different from other plants?

There are nearly 30,000 species of orchids in nature, and well over 100,000 man-made hybrids. The variation in sizes, shapes, and colors are staggering to the mind. With this much variation, what's the common denominator that makes them an orchid?

Besides the various parts of the plants such as the leaves, the roots, or even the pseudobulbs or rhizomes, there are two basic characteristics that define an orchid, and once you learn them you will see them repeated in every new orchid you come across. In many orchids, they are not obvious at first, but learning to recognize them is a lot of fun. To do so, we will have to look closely at the flowers.

The plant above and the flower to the right is a Cattleya orchid, the orchid that was used for corsages for the past hundred years. They're native to Central and South America where they grow as epiphytes and lithophytes. Its an orchid you'll encounter fairly often, and its fairly large so you can see the flower parts easily.

The parts of all orchid flowers occur in threes...three petals, and three sepals.

The sepals are the outside covering of the flower bud which opens, and they protect the petals inside. In an orchid, the third petal is always very different from the other two...so different that we don't call it a petal at all, we call it a labellum...or lip. The lip is involved with the polliation process, its used to guide the pollinator, whether its a bee, a butterfly, or a hummingbird, to the pollen. This lip is the first character that makes an orchid an orchid...all orchids have a lip.

To the left is a Phalaenopsis flower. Do you see the same flower parts? The lip is very different from the rest of the flower, but there it is.

You'll notice that near the center of the flower we have something labeled a "column". The column is the second character that makes an orchid an orchid. The column contains the reproductive organs...the "male" parts...the anther with its pollen...and the female parts...the stigma.

Orchids have very interesting and often bizarre ways to get the work of pollination accomplished. Pollinators are attracted to either the flower's color, its fragrance, or its shape. Some species of orchids have the shape and smell of a female wasp or fly and they are pollinated by the male wasp or fly trying to mate with it. Others have sweet fragrances to attract moths or butterflies, and others smell like rotting flesh to attract fly and beetle pollinators.

To get a good look at the column, we're going to have to remove the lip, which we did for the photo to the right.

The tip of the column is where the pollen is. The pollen is protected by the anther cap which comes off when the pollen is removed by the pollinator. The pollen is contained in tiny sacs called "pollinia" and the pollinia usually have a small amount of "glue" to help attach them to the pollinator.

Behind or below the anther cap is the stigma, where the pollen is deposited to accomplish pollination. Usually, the pollen is removed when the pollinator leaves the flower and then its deposited into the stigma of the next flower the pollinator visits. The stigma contains a sticky, sugary substance that traps the pollinia and holds it.

After pollination, the pollen grains extend small tubes which grow several inches down into the ovary where the eggs are which then become seeds. The ovary swells and can contain millions of seeds. Millions? Yes! Orchid seed is microscopic...like tiny flecks of dust...smaller than the period at the end of this sentence. Many orchids, especially the tropical ones, live high up in the treetops and the seed must be tiny and lightweight so that it can float in the air and land on another tree where it can grow.

Here's a close-up the column with its anther cap removed, the anther cap with its pollinia, and a single pollinia.

These belong to the Cattleya flower above, and Cattleyas are fairly large flowers, about seven inches across, with large pollinia...which are about 1/8th inch across. There are orchid species whose entire flower is only 1/8th inch across...just imagine how tiny their pollinia are.

The flower to the right is a Paphiopedilum, the asian ladyslipper orchid. Although it looks very different from the Cattleya or the Phalaenopsis, all the flower parts are there. The lip is shaped like a pouch, which is used to temporarily trap insects, and then the insects climb up the back of the pouch and slip past the stigma and then the pollen in order to escape. The two lateral sepals are fused into one. The flowers range in size from three to ten inches across.

 
Let's do one more orchid flower, the one to the left is a Gongora orchid. Its an epiphytic orchid from Central and South America. It produces long, pendant flower stems that hang straight down, carrying a dozen or so sweetly fragrant flowers that are upside down. (The "big" word for an orchid flower that grows upside-down is..."non-resupinate".) The lip is uppermost and the column hangs downward. The flowers are about two inches across.

Now that you've seen some few of the thousands of varieties, perhaps you're ready to recognize these two characteristics in other orchid flowers.

Have fun!



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