pteridomania

from The Century Dictionary.

• noun A mania or excessive enthusiasm in regard to ferns.

from the GNU version of the Collaborative International Dictionary of English.

• noun rare A madness, craze, or strong fancy, for ferns.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A craze, in 19th-century England, for collecting ferns and for using images of ferns in the decorative arts