Garden Mastery Tips
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March 2008 |
Native Orchids
Calopogon species, Grass Pink
For many gardeners, the word Orchid is scary. We think of them as tropical plants that only people using specialized techniques and greenhouses can grow, and we are sure that we have killed our share! However among the over 30,000 orchid species, there are over 200 species that grow wild in the woods and swamps of North America. There are even 25 species in Alaska! We can enjoy these beauties in their native environments if we know where to look and how to identify them. Exploring the native habitat and discovering orchids in the wild can be extremely rewarding and make for some interesting road trips! Some of these native beauties are now available to grow in our gardens here in the Northwest, and make stunning additions to the landscape. In this article, we will concentrate on growing the native species that adapt well to the Northwest garden.
First, a word of caution: native orchids are often rare or even endangered, and grow naturally only in specific habitats. The only way to legitimately obtain them is from a reputable nursery that grows them from seed or division, or rescues plants from destruction of habitat. Never dig them from their native habitat. The Washington Native Orchid Society website, http://www.wanativeorchids.com, has a list of Native Orchid Growers, including sources for purchasing native orchids.
Orchids native to North America are referred to as hardy terrestrial orchids. As with other plants, successful growth requires mimicking the native environmental conditions for the specific orchid; i.e. sun/shade, pH, and moisture requirements. William Mathis, Ph.D. in his book The Gardener’s Guide to Growing Hardy Perennial Orchids (http://www.wildorchidcompany.com/index.html) describes three groups of species: Upland, Transition, and Wetland. Upland species, like the Lady’s Slippers (Cypripedium species) grow best in some shade, and do not like constantly wet soil. Transition species, like Ladies Tresses (Spiranthes species) and Stream Orchids (Epipactus gigantea), tolerate constant moisture but can survive in drier conditions. Wetland species, like Grass Pink (Calopogon species) require constant moisture and full sun. Root systems of all orchids are especially susceptible to disease, and must have good clean water and access to air space, so all native orchids require excellent drainage. Even those that live in constant moisture must have soil that allows fresh water to continuously flow so that their roots are bathed in clean oxygenated water.
Epipactus gigantea, Stream Orchid
Soil drainage being key to growing hardy terrestrial orchids, the first thing a gardener must do is prepare the planting area. Choose a site that meets the sun/shade requirements of the species. The site must have good drainage. Excavate the area or use a raised bed and add rock to increase drainage. Pre-mix wood or leaf compost with sand and/ or PerliteTM as the basic planting medium. Often the nursery where the plant is purchased can supply you with the specific soil mix requirements of the species. Terrestrial orchids can be grown in containers, again with excellent drainage.
Water your orchids with low-chlorine, low-mineral content water. Rainwater works well. Orchids obtain their nutrients from compost and water, and do not need much, if any, fertilizer. Dilute fertilizer (about 25% of full strength) about once a month while actively growing is enough. Remove excess fertilizer by watering well. Browning of the leaf tips indicates over-feeding or mineral salt build-up in the soil.
Most of the terrestrial orchids bloom from May to June in our area. After bloom, cut back the flowers and allow the roots to gain strength from the leaf growth. The orchids will die back for the winter. Vernalization is a necessary part of most terrestrial orchids normal growth cycle. This means they require two to four months of temperatures below 40° F. to stimulate flowering the following year. When the plant dies back, mulch over with 1–2 inches of wood or leaf compost to protect them for the winter, and add nutrients for spring growth.
Cypripedium reginae, Showy Lady Slipper
Using these techniques, successful growth of many of the native orchid species obtained from nurseries is possible. Starting with a mature plant, rather than a seedling will give even more assurance of success, although the cost increases with the size of the plant purchased. As the techniques for orchid propagation are becoming more available to a wider variety of nurseries, the hardy terrestrial orchids will become a garden “must have”.
References
Brown, Paul Martin. Wild Orchids of the Pacific Northwest and Canadian Rockies, University Press of Florida, 2006.
Keenan, Philip E. Wild Orchids Across North America,Timber Press, 1998.
Mathis, William Ph.D. The Gardener’s Guide to Growing Hardy Perennial Orchids, The Wild Orchid Company, 2005. http://www.wildorchidcompany.com/index.html
Oregon Orchid Society. Native Orchids of Oregon, 2000.
Washington Native Orchid Society. (http://www.wanativeorchids.com)