The Jungle: Orchids and their velamen

Wall of Orchids at Longwood Gardens, displaying some of the diversity

The orchid family is one of the most diverse groups of flowering plants, essentially in a tie for first with the asters. They can roughly be split into two groups based on their growth habit: the terrestrial, or those that live in the ground, and the epiphytic: those that live aerially, often planting themselves in the crotches of branches of canopy trees within the jungle.

Paphiopedilum, a terrestrial orchid

The Jungle was the second biome featured in the Living Planet, and one I found particularly interesting as it depicts a compound ecosystem consisting of three distinct "stacked" habitats where an organism might live: the forest floor, the trunks of trees, or the canopy of these trees. The epiphytic orchids reside in this second layer: not planted in the ground as we tend to think of plants as always being, and not tall enough to have unrestricted access to the sun.

Due to their choice of habitat, the Orchids can't rely on ground water, so must instead draw water from the air of the humid environment around them. In order to accomplish this, they have modified roots, some of which are actually aerial, white or silvery-grey in color, and spongy in texture.  This color and texture results from a covering of velamen, actually the modified epidermis of the root which helps to absorb and hold in water.

An Aerial root on a Phalaenopsis I've acquired

These specialized roots are what often serve as a source of difficulty when many try to grow these in their homes. They assume that due to their native habitat the plant needs a lot of water, and overwater the plant resulting in these roots rotting. They do like this humid environment (some orchids actually wiliting as soon as they're removed from 70-80% humidity), but can't stand having their "feet wet", so to speak.

Probably the most common type of orchid grown, and probably the easiest as well, is the Phalaenopsis, or the Moth Orchid. The common name comes from the floweres, but I feel saying they resemble moths is an understatement. When I first had the opportunity to look at one of these flowers close up, I was taken aback by how accurate this mimicry seems to be, with the center of the flower so approximating the head and eyes of the insect.

Eye to eye, or rather eye column to with a Phalaenopsis

Aggregate of several Phalaenopsis at Longwood Gardens

Last time my Phalaenopsis flowered, I was curious enough to lift up the "moth face" (which is considered the "column" of the flower), curious as to what was underneath. Immediately upon lifting it up, two anther sacs popped out from underneath, exposing the reproductive parts of the flower. This stigma is further below in this structure. The pollinator would inadvertently lift up the "face" or cap of the column when inside the flower, then be covered with the pollen from the anthers, which would be deposited into the stigma when they do the same with another Phalaenopsis flower.

I wish I could show some detailed photos of the column, but couldn't this time around as I took all these at Longwood Gardens. Merkle's Orchids however has a great rundown on orchid flower morphology.

A hybrid containing Cattleya, another popular though more difficult orchid

I'm hoping to get a few more orchids for myself at some point. Planning on trying to grow a Paphiopedilum as well as a Bulbophyllum which I think I'll need to grow in a hanging basket. I was actually going to buy them last year but held off when I learned I'd be moving to Delaware, so I'll see if I can find the money this time around.

A little later this week we're going to revisit Tree ID, and learn how to identify a few Pines.