Asplenium vespertinum is a species of fern known by the common name western spleenwort. It is native to southern California and Baja California, where it grows in moist, shady, rocky places, such as the shadows beneath cliff overhangs.

The leaves grow in dense clusters and are up to about 30 centimeters (12 in) long. Each is made up of 20 to 30 narrow leaflets with lobed edges. There are a few sori on the underside of each leaflet.

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