Have you caught the orchid bug yet? When I first started my business, orchids were a rarity in the marketplace. Although there have always been excellent specialty growers, it was uncommon to see orchids for sale in most garden centers, never mind grocery stores and chain stores. Now, orchids are readily available. Yet these exotic looking plants intimidate most people. I used to be that way too, until last year when I was asked to assist in an orchid class. The instructor had an in depth knowledge of these plants and had grown hundreds of them. She agreed to teach the class but realized that teaching intimidated her. So, we formed the dynamic duo, taught the class together, and in the process, I took a crash course in orchids. What I learned absolutely fascinated me.
Basically, the majority of the world’s orchids live in tropical rainforests. There are hardy orchids here in Connecticut, most notably the lady slipper (Cypripedium) and Lady’s Tresses (Spiranthes). But those outdoor orchids are for another column. The orchids that we are focusing on in the winter months are the indoor orchids.
A majority of the tropical orchids are epiphytic. An epiphyte lives in the trees, supported by branches or trunks of the tree. It is NOT a parasite, but instead uses the tree for support and derives all of its nutrients from the rain and the air. Epiphytic orchids attach themselves by a series of strong aerial roots that not only cling to the tree but also grow out into the air. The outside surface of these roots is made up of a spongy material called velamen. As velamen ages and matures, it forms thick, corky, thin bark-like substance. The aerial roots of epiphytic orchids contain specific mycorrhizal fungi which, working in harmony with the plant (a symbiotic, or mutually advantageous relationship) help them convert the nutrients and minerals in the air and rainwater into food for the orchids. If you have ever closely examined orchid plants in a greenhouse, you most likely have observed these aerial roots. I find my customers automatically assuming that these plants need repotting, because they see “roots sticking out” of the pot. Now that you understand the growing habit of epiphytic orchids such as the common moth orchid (Phalaenopsis) you can understand why this would not be the case. Most epiphytic orchids have swollen storage areas on the plant to retain water during dry seasons.
Orchids that grow on the floor of the rainforest in soil or decomposing humus are called terrestrial. This is easy to remember as terra means earth. These usually do not have swollen storage organs and tend to derive their nutrients in a more “traditional” way, from the growing media itself.
The second basic classification of orchids that is vital to understand before you can begin to know their care is the way in which they grow. Sympodial orchids have a creeping growth habit. Podi means foot, and you can think of these plants as many- footed. These orchids crawl along the growing surface by a forming a long rhizome or thick, swollen, basal root-like structure. A rhizome is actually not a root at all, but instead is a modified stem that grows horizontally. Outdoor gardeners only have to think of bearded or German irises, as they too form rhizomes on the surface of the soil in the flower garden. Growing upwards from this rhizome are secondary stems. These mature in one season and it is from these stems that the flowers arise. When the stems of sympodial orchids are large and swollen, they are termed pseudobulbs. These are water storage organs and help these orchids to survive the naturally occurring dry spells in the rainforest. Examples of sympodial orchids are Cattleyas, Dendrobiums, and Cymbidiums.
Monopodial orchids do not form rhizomes and they do not have pseudobulbs for the storage of water. Instead, they grow from a single growing point in a fairly vertical fashion. Their leaves grow opposite each other along the main stem and aerial roots arise from along the entire length of the stem if the orchid is epiphytic. Because they do not have pseudobulbs for water storage, monopodial orchids grow where the water supply is fairly constant, without the extremes of the rainy season and dry spells. Those that grow in the shade have fleshy, succulent leaves. Those that thrive in the sun have thick stems and leathery leaves to conserve water. Examples of monopodial orchids are Phalaenopsis and Vandas.
If this sounds complicated, don’t panic! It really isn’t hard to understand. By starting with these basic facts you can slowly build up a basic understanding of these amazing plants and determine which are best suited to your home environment. In the next column we will learn about the cultural conditions that orchids need based on the botanical classifications explained above. In the meantime, go to your local library or bookstore and browse through the countless books on orchids that are now available. I have gleaned much of my information from an older reference, Rodale’s Encyclopedia of Indoor Gardening, edited by Anne Halpin. A more contemporary book that is fun to read is Orchid Growing for Wimps by Ellen Zachos.
This article was originally published in the Shore Publishing newspaper as a part of Nancy DuBrule-Clemente’s column “In the Garden”.
In an effort to provide horticultural information, these educational documents are written by Nancy DuBrule-Clemente and are the property of Natureworks Horticultural Services, LLC. You are granted permission to print/photocopy this educational information free of charge as long as you clearly show that these are Natureworks documents.