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-some 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 it into Thelypteris in 1967, and recent molecular work (Fawcett and Smith, 2021) has shifted it again into Pelazoneuron, though the older binomial remains the one in common horticultural use.
It is also one of the most adaptable native ferns in the American South. Its 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 it 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 when 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 our climate, going bronze at first frost and disappearing entirely by mid-winter, then unfurling fresh in April.
The fern travels by both short and long creeping rhizomes, which means a single plant will, given a few seasons, become a colony. It is the rare fern that genuinely earns the word groundcover — soft, continuous, and self-knitting, but not aggressive enough to overrun a planting. The Southern Living article that first sent gardeners looking for it in the 1990s suggested it could take full sun. It can, in the deeper South, provided the soil stays consistently moist. We plant ours in shade or semi-shade with rich, humusy soil and steady water through the first season, and recommend the same. Deer ignore it. It holds slopes near water exceptionally well. Pair it with hosta, heuchera, woodland phlox, trillium, and native azaleas, or let it run beneath high-pruned hardwoods as a clean green floor.