Yes. While some ferns enjoy moist soil and humid conditions, they should never be allowed to sit in water. Overwatering causes the leaves to turn yellow, wilt, and fall off. On the other hand, watering too little causes wilt, too.  Indoor ferns need to be watered only every ten days, while outdoor ferns need to be watered weekly. A fern that is planted in clay soil can be watered once every two weeks.