Sensitive Fern, Onoclea sensibilis L. , Minnesota native ferns, Eloise Butler Wildflower Garden

Onoclea sensibilis L.

Dryopteridaceae – Wood Fern family

Sensitive Fern grows in hardiness zones 2 to 10. The sterile fronds are pale sea-green in color and turn yellow in autumn. They are easily killed by frost and thus comes the common name "sensitive". Spores are produced on separate fertile fronds which are green in the growing season and turn brown in the autumn. The sori (spore producing organs) are bead like and arranged toward the top of these separate fronds, which persist through winter and release their spores the following spring. The sterile fronds are pinnatifid (the frond is once-divided with the divisions not reaching to the rachis [central stem]) to 1-pinnate (see photo for illustration). The leaves are quite broad and the veins form a network which is unusual in the fern world. The plant grows from a creeping rhizome in moist to wet soil, neutral to acidic and in sun or shade. They are fast growers and spread, thus needing frequent division if you wish to control them. In the garden they mix well with Siberian iris, hosta, or turtlehead. The fertile fronds work well in dried flower arrangements or provide winter interest in the landscape.

Above: Various shapes of the fronds. Note in right photo, the pinnea do not divide all the way down to the central rachis - referred to as "pinnatifid".

Below: The fertile fronds. Left - in the forming state in early August. The individual roundish structures are the "sori" - which contain the spore forming organs. Right - The developed fertile frond turning to the brown color of autumn (this one in early September). This frond will overwinter and release spores in the spring.

Below left: The emerging fiddlehead in late June.

Below center: The base of the fronds, emerging from the rhizome.

Below right: The fertile frond with developing "sori" in early September.

Below: Three views of the over-wintering fertile frond showing the mature round sori.

	Plants of the Eloise Butler Wildflower Garden
	Common Name	Scientific Name	Plant Family	Garden Location	Prime Season
	Sensitive Fern	Onoclea sensibilis L.	Dryopteridaceae – Wood Fern family	Woodland	Spring - Fall
Other names and notes	Sensitive Fern grows in hardiness zones 2 to 10. The sterile fronds are pale sea-green in color and turn yellow in autumn. They are easily killed by frost and thus comes the common name "sensitive". Spores are produced on separate fertile fronds which are green in the growing season and turn brown in the autumn. The sori (spore producing organs) are bead like and arranged toward the top of these separate fronds, which persist through winter and release their spores the following spring. The sterile fronds are pinnatifid (the frond is once-divided with the divisions not reaching to the rachis [central stem]) to 1-pinnate (see photo for illustration). The leaves are quite broad and the veins form a network which is unusual in the fern world. The plant grows from a creeping rhizome in moist to wet soil, neutral to acidic and in sun or shade. They are fast growers and spread, thus needing frequent division if you wish to control them. In the garden they mix well with Siberian iris, hosta, or turtlehead. The fertile fronds work well in dried flower arrangements or provide winter interest in the landscape.