Marah fabacea vs Marah oregana - an identification guide

I frequently see people attempt to identify Marah based on leaf shape, which is not a reliable technique. Marah leaves are incredibly variable, and you will often find more similarity between two individuals of completely different species than you will between two of the same species.

To demonstrate, compare the following selections of leaf shapes:

California Man Root, Marah Fabacea

Coastal Man Root, Marah Oregana

So how do you tell them apart? The key is in the flowers, fruits, and range.

California Manroot, Marah fabacea, is primarily found between Mendocino County and the Santa Barbara area, with some extension into the northern half of the Central Valley. Coast Man Root, Marah oregana, is found in coastal areas north of Santa Cruz. It extends northward all the way to Vancouver, and is the only Marah species known to occur in the Pacific Northwest.

Marah fabacea range

Marah oregana range

In short, if it's north of Northern Mendocino County it's probably not M fabacea, and if it's south of Santa Cruz it's probably not M oregana. 

(There are 3 other species of Marah in California as well - M watsonii circles the edges of the northern portion of the Central Valley, M horrida is found in the Sierra foothills from Sonora south to the Transverse Ranges, and M macrocarpa is found throughout SoCal south of the Santa Barbara area. I'll do more posts eventually on identifying these, but M oregana and M fabacea have the largest range overlap and thus are the most frequently misidentified).

When plants are in bloom, they can be distinguished by their flower shape, particularly when viewing the side profile of the flowers.California man root has flattish, plate-shaped flowers, and Coastal has cup-shaped flowers. 

California man root:

   

Coast man root:

   
   

The other major difference is the fruit. California man root has uniformly colored, round fruits, sometimes slightly wider than they are long, which are completely covered in stiff spines. Coast man root has elongated fruit which is shiny, has very few spines, and often has pale and darker green stripes.

California man root fruit:

Coast man root fruit:

Photo by ericah971 on iNat

If you find a Marah plant growing in an area where the ranges overlap, and it lacks fruits or flowers, it probably can't be accurately identified below genus level.