About Adiantum raddianum C.Presl
Adiantum raddianum C.Presl, commonly called the Delta maidenhair fern, is one of the most popular ferns grown indoors. It is native to South America, and its common name comes from its shiny, dark leafstalks that resemble human hair. This fern typically reaches 17 to 19 inches (43 to 48 cm) in height, and can grow up to 22 inches (56 cm) wide. In its wild native range, it grows on forest floors, in rock crevices, along river banks, on coastal cliffs, and on basalt banks beside trails and streams. Its triangular fronds start semi-erect, then droop gracefully as they mature; individual fronds can grow up to 12 inches (30 cm) long and 6 inches (15 cm) wide. The genus name Adiantum comes from the Greek word "adiantos", which means "unwetted", a reference to the fern's leaves. This species is only hardy down to 5 °C (41 °F), so it must be grown indoors in temperate regions. It can be placed outside in a sheltered spot during the summer months. It requires high humidity, well-drained soil, bright indirect light, and a fairly constant temperature. It prefers neutral or slightly alkaline soil, and is suited to USDA hardiness zones 10 and 11. It can be prone to infestations from scale insects and mealybugs. Two cultivars, ‘Brilliantelse’ and ‘Kensington Gem’, have received the Royal Horticultural Society's Award of Garden Merit. A. raddianum is sometimes classified as an invasive species in Hawaii and French Polynesia.
