Kingdom: Plantae
Division: Pteridophyta (Filicophyta)
Class: Osmundopsida
Order: Osmundales
Family: Osmundaceae
Genus: Osmunda

Osmunda claytoniana

Common name: interrupted fern

(Drawing from How to Know the Ferns by Frances Parsons)

The interrupted fern is a beautiful plant, with softer foliage than its similar cousin, the cinnamon fern. The interrupted fern is so-called because the highly-modified pinnae which bear the spore, which have the lamina entirely replaced by sporangia, are in the middle of the frond. After the spore ripens and these pinnae wilt, a gap is left in the pinnae of the frond.

The interrupted fern is pinnate-pinnatifid, with the lobes being more rounded than on the cinnamon fern. On large, well-developed specimens, smaller sterile fronds first form a vase-like appearance, with the larger, fertile fronds then forming a secondary vase inside.

You'll most often find this plant in moist pockets on hillsides, and especially on moist, well-drained shelves above sandstone ledges, in humus-rich soil.

The only hybrid known within the genus Osmunda is between the interrupted fern and the royal fern, O. regalis, which is ironic since these two are usually placed in separate sections of the genus while the cinnamon fern, which does not hybridize with the interrupted fern, is placed in the same section! However, the hybrid, known as O. Xruggii, is rare, only ever having been found twice.

This is a good fern for the garden, but appreciates rich soil which is not allowed to dry out.


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This page was last revised on 11-10-1997.