Thelypteris palustris (Marsh Fern)

A confirmed deer-resistant fern with a genuinely singular ecological relationship, marsh fern is the only known host plant for the Marsh Fern Moth (Fagitana littera) - an exceptional degree of larval specificity for any plant in this catalog, let alone a fern.

Species Overview

Thelypteris palustris, or marsh fern, is a deciduous fern native to wetlands across eastern North America and Eurasia, with erect to ascending, finely-textured, light green fronds reaching 1 to 2 feet tall. Unlike most ferns, it prefers sunny wetland habitats, spreading by creeping rhizomes to form dense colonies along streams, ponds, and marsh margins.

Application

• Sunny wetland, stream, and pond-margin restoration - unusual among ferns for tolerating full sun
• The sole documented larval host for the Marsh Fern Moth
• Deer-pressured wetland plantings
• Woodland garden and water garden massing plantings

Growing Conditions / Specification Data

• Light: Full Sun to Part Shade
• Soil/Moisture Tolerance: Wet, sandy, acidic soils; moist to wet conditions
• Plant Type: Fern
• Mature Height: 1-2 ft.
• Fall Color: Insignificant/None - deciduous
• Wetland Indicator Status: OBL (Obligate Wetland)
• Native Range: Northeast/Mid-Atlantic (full list)
• Hydrology: Moist-Wet
• Root Depth: Shallow (Under 12 in.)
• Salinity Tolerance: Low
• Growth Rate: Rapid
• Drought Tolerance: Low
• Flood Tolerance: High - Rated Moist-to-Wet hydrology in a formal stormwater vegetation reference table, consistent with this species' already-confirmed saturated-soil tolerance from earlier work.
• Shade Tolerance: Tolerant - prefers shade, tolerates sun with ample moisture
• Growth Habit: Spreading - creeping rhizomes
• USDA Hardiness Zones: 5-8
• Deer Resistance: Yes (Rarely Damaged)
• Pollinator Value: Larval host, supports moths

Planting Guidance

• IMPORTANT: the only known host plant for the Marsh Fern Moth (Fagitana littera) - exceptional larval specificity worth highlighting for insect-focused restoration work. Spreads by rhizome to form dense colonies; does not tolerate excessive standing water or heavy shade despite its wetland habitat.