A fernery, is, as its name implies, a specialised garden featuring ferns.
Ferns are found in rainforests, so they have specific climatic needs and cannot survive in adverse conditions. They are frost, heat, and light-sensitive, so In many countries ferneries are indoors or at least sheltered or kept in a shadehouse to provide a moist environment and filtered light.
Because ferns are tricky to grow and propagate, ferneries are usually maintained by more experienced gardeners and horticulturalists.