Ophioglossum petiolatum or Stalked Adder's-Tongue Fern is a very small fern found naturalized in Florida northward to Virginia and westward to Oklahoma and Texas. The fern also occurs in the West Indies, Mexico, Northern South America, Tropical Africa, India, China, Japan, Philippines, and New Zealand to name just a few locations. Most likely the fern was introduced to the U.S. through the horticulture trade. In containers, the fern remains very small, with its 2-3 sterile fronds about 1.25 inches (3.2 cm) long and about 0.50 inches (1.3 cm) wide. Leaves are erect to spreading, with broadly lanceolate leaves with an acute apex. We are not quite sure how this fern got introduced into the greenhouse. At first glimpse, it is a welcome visitor, but such spontaneous plants can become greenhouse pests with a strong likelihood of becoming invasive. The fern is hardy in USDA zones 5-10.
Blooming: Fertile fronds are up to 4 inches (10 cm) long, tipped with a cylindrical fertile spike that resembles the rattle of a rattlesnake, but much smaller, elongating to 0.75 inches (1.9 cm) long.
Culture: Ophioglossum petiolatum needs a moist fertile soil with full sun to partial shade. In the greenhouse, we use a soil mix consisting of 2 parts peat moss to 1 part loam to 1 part sand or perlite. Plants are watered and allowed to dry slightly before watering again. Due to the need of mycorrhiza to grow properly they are not fertilized. Once the fern dies back, pots are kept fairly dry until new ferns pop up. With the use of supplemental lighting you can have this cute fern all year long in the greenhouse. Just remember that they can become very weedy.
Propagation: Ophioglossum petiolatum are propagated by division of large colonies or from spores. Spores need total darkness to germinate and unsterilized soil because of the mycorrhizal symbiont.
Ophioglossum petiolatum was featured as Plant of the Week December 3-16, 2010.
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Cal's Plant of the Week was provided as a service by the University of Oklahoma Department of Microbiology & Plant Biology and specifically the late Cal Lemke, who used to be OU's botany greenhouse grower and an avid gardener at home as well. If the above links don't work, then try the overview site. You may also like to look at the thumbnail index. ©1998-2012 All rights reserved.