The feasibility of later-generation hybrid production in ferns has not been previously studied, although it is a significant factor in relation to reproductive isolation. Osmunda x intermedia, a hybrid between O. japonica and O. lancea, is semifertile and has moderate spore germination rates. Under the artificial conditions of this study, F2 and F3 offspring were formed. Some of the F2 offspring showed precocity, and some of the F3 offspring also showed precocity. This fertility suggests that introgressive hybridization might be ongoing in nature. This also indicates a currently unknown genetic control over the timing of fertile frond production in Osmunda.