Greenhouse propagation of the endangered hemiparasite Schwalbea americana (American chaffseed): experimentation and botanical studies

Schwalbea americana pictured during spring 2016 after a fire at the Woods Bay HP restoration site. Displayed is one of the plants that we grew and outplanted. In addition to the large flowering and non-flowering S. americana plants, note the native host plant—Pityopsis graminifolia (Michx.) Nutt. (Asteraceae; narrowleaf silkgrass)—surrounding the chaffseed. Photo by Jeff Glitzenstein

Timeline of the Schwalbea americana research and botanical observations conducted with a single cohort of seeds from 2 South Carolina source populations. Schwalbea americana is an endangered species, therefore any plants alive after an experiment were made available to restoration professionals. In addition, several hundred plants not used in experiments were also grown and made available to restoration professionals. Approximately 2000 S. americana plants were successfully germinated and grown ex situ during this 21-mo series of experiments.

Greenhouse seed germination and establishment experiment, 2013–2014. Photo by Danny J Gustafson

Average number of Schwalbea americana plants (± 1 SE) from 2 different source populations (Longlands and Scotswood Plantations, SC) growing in commercial (Jungle Grow) and nursery growth media, with (shaded lines) and without native soil microbes introduced. There was a significant three-way interaction (F^1,287 = 7.60, P < 0.01) among population source, growth media, and microbe addition. Addition of microbes differentially affected Scotswood plant establishment based on the growth media. Error bars represent one standard error of the mean.

Significant Schwalbea americana population source by growth media (F^1,387 = 3.83, P = 0.05) (upper) and population source by microbes (F^1,387 = 4.90, P = 0.03) interactions (lower). Bars represent average height (cm) and the error bars represent one standard error of the mean.