Common Pyrrosia , P. lingua var lingua (The original Japanese Tongue Fern) is extremely easy to cultivate. I have maintained this variety for over 30 years and have never experienced any problems with its care. It is extremely vigorous, and produces very large fronds and is totally cold hardy, enough that any area in the southern US could cultivate this fern in the ground out doors and never worry about winter loss. At maturity, individual leaves can be 16 inches long and 3 inches wide. The fronds are fairly symmetrical with very little twisting of the blade. It is mostly fertile and very commonly produces fertile fronds with spores.