Thelypteris kunthii

The southern shield fern carries a longer pedigree than most ferns in cultivation. The type specimen was collected by Alexander von Humboldt and Aimé Bonpland near Cumanacoa, in the cloud-shrouded country around Caripe in northeastern Venezuela, during their five-year expedition through the equinoctial Americas. Decades later the German botanist Carl Sigismund Kunth, Humboldt's assistant in Paris and the man who would spend years describing the ten thousand and more specimens the explorers shipped home, became the namesake when Nicaise Auguste Desvaux formally described the species in 1827 as Nephrodium kunthii. C.V. Morton moved the fern into Thelypteris in 1967, and recent molecular work (Fawcett and Smith, 2021) has shifted the name again into Pelazoneuron, though the older binomial remains the one in common horticultural use.

This is also one of the most adaptable native ferns in the American South. The range runs from the fall line in the Carolinas across the Gulf Coast to east Texas, and on through the Caribbean and Mesoamerica into northern South America, essentially tracking the warm, humid, summer-rich half of the New World. In the wild the fern turns up on shaded streambanks, in rocky woodland, along sinkhole walls, and in the soft alluvial soils of bottomland forest. The fronds are pale, almost sea-green as they emerge in spring, finely cut, slightly triangular in outline, and rise in upright, arching clumps to three feet, occasionally four in rich ground. They are deciduous in the Upper South, going bronze at first frost and disappearing by mid-winter, then unfurling fresh in April.

The southern shield fern travels by both short and long creeping rhizomes, so that a single plant will, given a few seasons, become a colony. This is the rare fern that genuinely earns the word groundcover, soft, continuous, and self-knitting, yet not aggressive enough to overrun a planting. The Southern Living article that first sent gardeners looking for the fern in the 1990s suggested the plant could take full sun, which holds in the deeper South, provided the soil stays consistently moist.

Woodlanders plants ours in shade or semi-shade with rich, humusy soil and steady water through the first season, and recommends the same. Deer pass the fronds by, and the fern holds slopes near water exceptionally well. Pair the southern shield fern with hosta, heuchera, woodland phlox, trillium, and native azaleas, or let the colony run beneath high-pruned hardwoods as a clean green floor.