Flowers have bright yellow petals with pale brown or violet veins. There are no bracts on the inflorescences. The entire, mature fruit is 3.5-8.5 cm in length. The fruiting pedicel is rarely erect. The fruit contains a single row of 8-10 seeds.
Seeds are subspherical to oblong and can be black or brown in color.
The fruiting C. monensis plants growing in Humboldt Co., California ranged from 4 cm to 1 m tall. Basal rosettes varied from 2 to 40 cm in diameter. Coincya is very similar to a number of other mustards found in eastern North America. In contrast, Coincya inflorescences generally lack bracts, and the fruit-beaks are broad and somewhat flattened. While the flowers of Sinapis has uniformly colored petals and spreading sepals, Coincya petals have colored veins and the sepals are erect and converging.