Osmunda, also referred to as the "flowering fern," is a genus of ferns that can survive in a wide range of climates and appear to flower when the spores begin to change color. The group consists of approximately ten different species, with the most commonly known being the cinnamon fern, the interrupted fern, and the royal fern. It is uncertain where exactly the name "Osmunda" came from, but one theory suggests it comes from Saxon mythology. The Saxon god Osmunder, the equivalent of Thor from Norse mythology, hid his family inside a large group of ferns to protect them from danger, and thus the ferns were referred to as Osmunda after the great god.
Ferns in the Osmunda genus grow in climates both freezing and tropical, survive in sun or shade, and can tolerate certain wet or dry soils. The fern's fronds grow large and leafy in appearance. The term "flowering fern" comes from the misconception that the ferns produce flowers. What actually happens occurs due to the way the ferns reproduce.
Typically, a fern creates tiny spores on the undersides of its fronds, or leaves, which the wind carries away to grow away from the parent fern. In the Osmunda genus, instead of producing small, dot-like spores underneath the leaves, the ferns produce rusty-red, large, spherical clusters on top of the leaves. All the clusters appear at the same time and soon drop off, causing the fern to appear as if it has flowered. Many of the ferns themselves also turns a yellow or reddish color in the fall.
The most popular fern in this group is the royal fern. Originally grown in Europe, its scientific species name is "regalis" and forms thick clusters of leaves. It can grow up to 63 inches (160 cm) tall. Another common Osmunda fern is the interrupted fern, scientifically known as the "claytoniana." It grows tall and straight, and takes its name from the spores which form halfway up the fronds and seems to interrupt the green pattern of the fronds.
Finally, the Cinnamon Fern, known as cinnamomea, is widely known for its red colored fronds which appear only in the middle of the plant and grow straight up. The red fronds appear to be flowering and it is the most likely of the group to be confused for a flower instead of a fern.
For the ferns to grow properly, they need nutrient-rich soil, and extra moisture if placed in sunlight. Shadier areas can support ferns in dryer soils. Each fern thrives in a different range of temperatures. Gardeners should research ferns available to them and see which thrive in their climate zone as well as what specific requirements for that fern might differ from the others in the Osmunda genus.