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Linda Naeve, Reiman Gardens, (515) 294-8946,
Jean McGuire, Continuing Education and Communication Services, (515) 294-7033,

Oncidium Orchids Make Good Cut Flowers and Houseplants

Linda Naeve
Extension Coordinator
Reiman Gardens

What do anthuriums, bird-of-paradise, ginger and oncidium orchids have in common? They are tropical plants with flowers that are not only beautiful, but make excellent cut flowers in exotic floral arrangements. We commonly see orchids, such as the cattleyas or cymbidiums, used by the floral industry as single blossoms for corsages on Mother's Day and other special events. However, orchids with spikes containing several flowers, such as oncidium and dendrobium orchids, are gorgeous and last several days in a vase.

This week's Reiman's Pick, oncidium orchids (pronounced on-sid-EE-um), is a genus that contains more than 600 species. Many species produce long, branched spikes containing dozens of dainty flowers. Oncidium varicosum, is one of many species that is referred to as "dancing dolls" because it produces up to two hundred delicate flowers on a 5-foot long, branched spike. A young visitor viewing the Reiman Gardens' Orchid Show appropriately described a bright, yellow-flowering oncidium as a "branch covered with butterflies."

Most oncidium species are epiphytes, which mean they are not soil dwellers. They are native to tropical forests where they have adapted to living high in the tree canopy because of lack of sunlight on the forest floor. Epiphytes only use the trees for support, they are not parasites on the trees. Many epiphytic orchids have aerial roots that are covered with a layer of dead cells known as the "velamen," which absorb water from the humid atmosphere. When filled with water, the velamen becomes transparent allowing light to reach the green tissue in the roots, triggering photosynthesis. Epiphytic orchids absorb nutrients from dust washed off of tree leaves by rainwater.

Since they are not adapted to soil culture, oncidium orchids and other epiphytes need a loose, well-drained growing medium. An all-purpose orchid medium contains one part perlite, one part coarse sphagnum peat moss and six parts pine or fir bark in 1/4- to 1/2-inch pieces. It may be necessary to repot oncidium orchids every two years. Ideally, they should be repotted immediately after flowering, and the growing medium should be kept moist at all times.

Oncidium orchids have a "sympodial" growth habit in which a rhizome grows along the top of the medium from which new shoots and roots sprout. Like many sympodial orchids, the stem on the oncidium orchid has a thickened portion called a pseudobulb, which functions as a water and food storage device.

Oncidium orchids thrive in bright light, such as an east-facing or a lightly shaded, south-facing window. They prefer warm temperatures during the day and cool night temperatures between 50 to 60 degrees F.

The long arching spikes of oncidium orchids can be staked upright to enjoy the beauty of the flowers. You can see dozens of onicidium spikes rising above the tropical ferns during the Orchid Show in the conservatory at Reiman Gardens, through October 19.

To learn more about the Reiman Gardens at Iowa State University visit us on the Web at:


Reiman Gardens Orchid Sale
Saturday, Oct. 25, 9 to 4 p.m.
More than 300 orchid plants, novelty and hybrids of various species will be available for sale. Non-members must pay admission to be admitted to the Orchid Sale.

Editors: A color photo, suitable for publication, is available at right. Click on the thumbnail photo to go to the fullsized photo. The picture's fullsize photo is 296K.

Caption: Oncidium Orchid


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