Boston Fern, Nephrolepis exaltata
Holly Fern, Cyrtomium falcatum
Nephrolepis ferns are a good choice for a groundcover under oaks and in shady locations.  There are many varieties of different sizes and shapes available.  Clumping ferns need to be removed periodically to maintain them within their bounds.
Use Japanese holly fern in place of the traditional Boston fern for a more unique look.  Holly fern is more tolerant of sunlight then other ferns.
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Alex Driscoll
Certified Arborist #1249A
Plant Guide / Groundcovers / Boston Fern