Culture
This is a perennial fern that is winter hardy to USDA Zones 10-11. In the St. Louis area, it is typically grown as a houseplant, where it seems to respond best in bright indirect light including diffused sun, but dislikes direct sun. If grown in full shade, foliage will lose its vitality. Use a consistently moist but well-drained potting soil. Roots must never be allowed to dry out. This can be a difficult plant to grow in St. Louis because it needs a very humid atmosphere. Avoid placing plant in drafty areas or in locations near heat registers. Pots may be set in a tray of wet pebbles to increase humidity. Consider siting pots in bathrooms where atmospheric humidity is generally higher. May be grown as a houseplant year around, but sometimes benefits from a winter rest. Remove any browned foliage immediately.
Noteworthy Characteristics
Adiantum raddianum, commonly called Delta maidenhair fern, and its cultivars are perhaps the most commonly grown of the non-winter hardy maidenhair ferns. Triangular, 3- or 4-pinnate fronds with dark stalks emerge from a dense rootstock of short, branching rhizomes. Fan-shaped pinnae (leaflets) emerge light green but darken with age. Fronds typically grow to 12” wide and 18” long. Cultivars of this species come in different colors, shapes and forms. Synonymous with and formerly known as Adiantum cuneatum.
Genus name comes from the Greek word adiantos meaning unwetted in reference to the water repellent foliage.
Specific epithet honors Italian botanist Giuseppe Raddi (1770-1829).
Problems
Watch for scale and mealybugs. Leaves may scorch in direct sun. Fronds will die back quickly if soils are allowed to dry out.
Uses
Houseplant that may be considered for bathroom areas and bright areas with some diffused sun. Hanging baskets, pots or containers.