INTRODUCTION TO ORCHIDS

Background

Orchids are members of the family of monocots known as Orchidaceae. This is by some accounts the most diverse family of plants in the world, with over 25,000 species. Here are a couple of quick facts that give an idea of the size of the orchid family: between 6 and 11% of all species of seed plants are orchids, and there are about four times the number of species of orchids as there are mammals on the planet (Pillon and Chase, 2007). The vast majority of these species are found in the humid tropics (like here in the islands!) but you can find orchids nearly everywhere on earth except for glaciers–even some deserts and tundra host some orchids (Schuiteman, 2014).

The enormous amount of species of orchids has made their classification difficult, to say the least. Among the most popular of the over 800 genera are the Phalaenopsis, which has a monopodial growth habit, meaning that it grows straight up from the roots into a single stem (Rogers, 2012).

The Cattleya orchids, on the other hand, have a sympodial growth habit, meaning that they have a modified stem called a rhizome from which multiple stems arise. The rhizome also stores water, so this type of orchid, when cultivated, has different watering requirements (Rogers, 2012).

The Paphiopedilum, also sympodial orchids, are known as lady slippers, due to the pouch-like structure on the flower. This structure fills with sap that traps insects, who are then obliged to climb up over the flower, pollinating it (2012). Clever!

Cypripedium is another sympodial orchid, also known as lady slippers, but these are mostly native to temperate North America, Asia, and Europe, while the Paphiopedilum are a tropical Asian species (Rogers, 2012).

Most orchids, like those above, are grown purely as ornamental plants or for cut flower production, but they have other uses as well. The Vanilla genus of orchids produces an extremely important flavoring agent, one of the most valuable spices in the world (CNN, 2015). Some East Asian cultures use various species of orchids for medicinal purposes; excessive collection for both medicinal and horticultural uses has threatened the survival of some endangered orchid species (Schuiteman, 2007).

PROPAGATING ORCHIDS

There are certain aspects of orchids’ lifestyles that require special treatment when propagating and growing them. In nature, many orchids are epiphytes, growing on other plants, and some are terrestrial, growing in the ground. The epiphytes are not parasites of the plants they grow on—they obtain water, air, and nutrients from the surrounding environment—but it does make them unusual in that their roots grow in the air instead of in the ground (Rogers, 2012). Hey, I’m not gonna judge them, mon. Additionally, in their natural environment many terrestrial orchids form mutually beneficial relationships with fungi, which are required for the orchids’ seeds to germinate. Many times the seeds do not contain any nutrients for the embryos, unlike almost all other seed plants. The fungus provides nutrition for the embryos; in the absence of the fungus, as is the case when you are cultivating orchids, special measures must be taken to germinate the seeds (University of Sydney, 2004). The seeds must be grown in culture that provides nutrients; a disadvantage of this method of propagation is that the seedling that is produced will then take many years to flower (Hartmann et al, 2011).

Some sympodial orchids, such as the genus Dendrobium, develop enlargements on the rhizome, called pseudobulbs, which can be removed and grown into new plants (Hartmann et al, 2011). Some other sympodial orchids can be propagated by simply slicing off part of the rhizome and growing it (Chugh et al, 2009). These and other vegetative methods work well with some species at some times, but the most success with propagating orchids will be achieved by tissue culture.

Now listen up, brethren and sistren, I’m gonna speak the truth. Tissue culture is hard. It’s even harder if you don’t have a lab. But here’s the deal with orchids: some of them are very rare and very, very expensive. And with tissue culture you can turn one orchid into thousands, if it works. So it might be worth the effort.

The first thing, and the main thing, is you have to be really, really clean, or it’s just not going to work. Everything in the vicinity of your work area–the table, the tools, your hands–clean everything with alcohol. Before you do that, even, sweep the floor and dust everything. Close that window. Kick out the cat. Anything floating around in there could contaminate your culture.

You need a sharp scalpel or other very sharp blade, and some forceps or tweezers (sanitized!). You’ll probably have to order the rest of your supplies. Get some petri dishes, paraffin tape, and specially-made orchid nutrient medium from an online supplier. Follow the manufacturer’s instruction to prepare the medium in the plates. Remember to clean everything! That nutrient medium for your plants is also the favorite food of bacteria, so instead of this:

You will end up with this if you don’t keep everything clean:

And that is no good for growing plants. Ok, now you have the plates ready to go on your nice clean work area. Choose the plant you want to reproduce, find a young shoot, and slice it off. Drop that guy in a 10% bleach solution for 15 minutes and rinse with sanitized, or at least distilled, water (Hort 202 staff, 2015). Sanitize your blade and forceps by dipping in alcohol and then lighting on fire for a couple of seconds. Allow them to cool, but make sure you don’t recontaminate them while they’re cooling! Place the sanitized shoot in a new, empty, sterile petri dish and hold with your forceps while slicing off the thinnest layer you can manage. With the forceps, place this slice on the medium in a petri dish, and close the dish and seal it with parafilm. If you keep this dish closed in a dark, warm place for about 9 months or so, with some luck the slice of shoot will produce some “protocorm-like bodies,” little knobs that each have the potential of growing into a plant. Using the same sterile technique, these can be separated and either micropropagated into more clones or allowed to grow into orchids.

Good luck!

Sources

Chugh, Samira, Satyakam Guha, and I. Usha Rao. “Micropropagation of orchids: A review on the potential of different explants.” Scientia Horticulturae  122. (2009): 507–522.

CNN Money. “The World’s Priciest Foods.” Cable News Network (2015).

Hartmann, Hudson T., Dale E. Kester, Fred T. Davies, and Robert L. Geneve. Hartmann & Kester’s Plant Propagation Principles and Practices (8th ed.). Upper Saddle River, NJ: Pearson Education, 2011.

Horticulture 202 staff. “Tissue Culture: Lab 7.” Pennsylvania State University (2015).

Pillon, Yohan, and Mark W. Chase. “Taxonomic Exaggeration and Its Effects on Orchid Conservation.” Conservation Biology 21.1. (2007): 263-265.

Rogers, Bruce. The Orchid Whisperer: Expert Secrets for Growing Beautiful Orchids. San Francisco: Chronicle, 2012.

Schuiteman, André. “Biodiversity and conservation of orchids: the importance of Kew’s fieldwork.” Kew.org blog post. Royal Botanic Garden, Kew (2007).

University of Sydney. “Function of Orchid Mycorrhizas.” University of Sydney (2004).

Cover photo courtesy of Reggae Marathon Ltd.