An intricate M. watsonii leaf with pointed
lobes in front of a greyblue-green stem

Marah watsonii is also called Taw Manroot. Its range is the northern counterpart to M. horridus covering an arc around the northern end of the Central Valley from the coast range around to the central Sierra Nevada foothills where the ranges of M. watsonii and M. horridus overlap.

M. watsonii has the most distinctive and ornate foliage of the genus. Leaves are deeply and intricately dissected with pointed or rounded lobes. Along with an unusual leaf-shape, the stems of M. watsonii are distinctively greyblue-green and nearly hairless.

Young leaf and female flower with male
bloomstem just starting to emerge.

Flowers are bellshaped with flattened white petals. Male bloomstems have fewer flowers than other manroots with widely spaced blooms on long stems. Single female flowers hang from the base of the bloomstems with a small, very smooth unfertilized fruit at their base.

Fruit with sparse and robust,
hornlike spikes

M. watsonii fruit are also distinctive: Usually round, the fruit hang from thick stems and show the least dense and most robust spikes of the genus. Some populations lack spikes entirely while others have sparse, robust, hornlike spikes. Seeds are somewhat more spherical than the genus-typical bullet shape, but are typically smooth and grey-brown.