Wednesday, July 25, 2012

Stanhopea Morphology

For many of you who grow Stanhopeas, the specific botanical terminology used to identify parts of orchid plants may not be particularly interesting.  However, several species of Stanhopea differ dramatically in physical characteristics.  I think it is always a good idea to know and learn as much as you can about the plants that you are growing to ensure you can accurately identify them to species.  This will give you a great advantage in knowing what conditions the plant would prefer, ensuring that the plant will grow to ultimate size and maturity, and providing you with several blooms.  It will also reduce the chances that you will purchase a plant and not be able to provide the proper conditions to allow the orchid to grow and bloom.

I will be using some botanical terminology from time to time to discuss the physical characteristics of these orchids, so I thought it would be appropriate to provide a post that outlines some of this terminolog.

Stanhopea anfracta flower
Orchids have four main parts to the flower and these include the sepals, petals, labellum (lip), and column. The sepals in Stanhopeas are some of the largest flower structures and are the outer most portion of the flower. The next inner structures are the petals, which are usually thin and often ribbon-like and twist or roll back when the flower is mature. The next inner structure  is the lip which has three parts. The upper portion of the lip that is connected to the rest of the flower is called the hypochile, and is often rounded, cupped, or cylindrical. This is the part of the orchid where the fragrance is produced. The central portion of the lip is called the mesochile and is usually a short piece of tissue that usually has two projections attached to it that are called horns (absent in the hornless species). The lower portion of the lip is called the epichile and is usually spade shaped or tri-lobed depending on the species.   


The column in orchids is the organ where the reproductive parts are placed, is the union of both male and female structures, and is the innermost structure.  In Stanhopeas, the column is an elongated cylindrical organ that creates a tight space between the horns and epichile that allows the pollinating insect to be positioned so that the pollen cap is removed, and the pollen sac deposited on the back of the insect. This action also opens access to the stigma to allow pollination to occur by the next insect carrying a pollen sac.

Stanhopea graveolens pseudobulb

Stanhopeas have pseudobulbs that sit at the surface of growing medium and are often rounded or egg shaped. These storage organs are used to store water and nutrients for the plant. The larger the pseudobulb, the more mature the plant is, and the more likely that the pseudobulb will produce an inflorescence (flower stalk). At the top of the pseudobulb is the cylindrical base of the leaf called a petiole, and at the top of that is the blade of the leaf. Below the pseudobulb, roots are produced to allow the plant up take up nutrients and water.

Stanhopea embreei leaf
Leaves of Stanhopeas can be large and widely lanceolate in shape or smaller and almost linear.  Stanhopea leaves can be rather thick and leathery or in some species thin and delicate.  The larger leaved and thin leaved species ( e.g., S. embreei and S. insignis) seem to tolerate less sun, while the narrow and leathery leaved species (e.g., S. oculata and S. tigrina) tolerate a bit more sun, though they can still burn easily in part day sun. Part shade to full shade is best for most species, and I have found an hour or two of very early morning sun tolerated by most species.

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