Dryopteris intermedia

Species Native to Missouri
Common Name: intermediate wood fern 
Type: Fern
Family: Dryopteridaceae
Native Range: Northeastern United States
Zone: 5 to 8
Height: 1.00 to 3.00 feet
Spread: 1.00 to 3.00 feet
Bloom Time: Non-flowering
Sun: Part shade to full shade
Water: Medium
Maintenance: Low
Other: Winter Interest
Tolerate: Rabbit, Heavy Shade, Clay Soil

Culture

Easily grown in average, medium moisture, well-drained soils in part shade to full shade. Prefers fertile, moist, humusy loams that are rich in organic matter. Best with consistent moisture. Soils should not be allowed to dry out. Site in locations protected from strong winds to prevent damage to the fronds. Tolerant of high humidity. Fronds are evergreen to semi-evergreen in mild winter climates, but deciduous in the St. Louis area. Where deciduous, the old fronds should be cut off in late winter prior to the emergence of the new growth. Propagate by division or spores.

Noteworthy Characteristics

Dryopteris intermedia, commonly called evergreen wood fern, glandular wood fern to fancy fern, is a rhizomatous wood fern that is native to moist woodland areas, ravines, swamp margins and rocky slopes in Eastern North America from Newfoundland to Ontario to Minnesota south to Missouri and Georgia. It is common through much of its range, but uncommon in Missouri where it is typically found on shaded ledges and sandstone bluffs. It was formerly known as Dryopteris spinulosa var. intermedia, and is very similar in appearance to Dryopteris carthusiana (formerly known as Dryopteris spinulosa) from which it is primarily distinguished by (a) length of pinnules on lowest pair of pinnae being usually shorter than the length of the next pinnule and (b) glandular leaf blades.

This is a lacy evergreen wood fern that typically grows to 1-3’ tall with upright arching fronds to 40” long and 8” wide. Frond leaflets are lobed and toothed. Oval to narrow triangular, thrice-cut, finely dissected blade has 10-15 pairs of narrow lance-shaped pinnae (leaflets). Sori (fruit dots) appear on the leaflet undersides on fertile fronds in early to mid-summer.

Genus name from Greek dryas meaning oak and pteris meaning fern in reference to the presence of some species of wood ferns in woodland areas populated with oaks.

Specific epithet means intermediate in probable reference to this fern being between D. carthusiana and D. campyloptera.

Problems

No serious insect or disease problems.

Garden Uses

Excellent fern for woodland or shade gardens. Containers, borders, rock gardens. Grow along shaded walls or buildings. Mass in shaded areas. Tolerates dryish slopes.