In favourable conditions the royal fern will grow into regal size. Among the native Finnish ferns, an old lady fern rootstock may grow 1.5 metre tall fronds but still not reach as high.
The sterile fronds of royal fern make a leguminous impression but it soon disappears on the discovery of the fronds with tassel-like clusters of spores, hence the English nickname Flowering Fern. The green sori turn brown by autumn. In deep shade there will be less of these fertile fronds. The royal fern spreads via rhizomes and spores.